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09

Technical Design Guide issued by Forest and Wood Products Australia

Timber FlooringDesign guide for installation

WoodSolutionsisanindustryinitiativedesignedtoprovideindependent,non-proprietaryinformationabouttimberandwoodproductstoprofessionalsandcompaniesinvolvedinbuildingdesignandconstruction.

WoodSolutionsisresourcedbyForestandWoodProductsAustralia(FWPA).ItisacollaborativeeffortbetweenFWPAmembersandlevypayers,supportedbyindustrypeakbodiesandtechnicalassociations.

ThisworkissupportedbyfundingprovidedtoFWPAbytheCommonwealthGovernment.

ISBN978-1-921763-19-9

Prepared by:DavidHaywardAustralianTimberFlooringAssociation

Firstproduced:April2009Revised:August2010,May2012

01


Timber-framed Constructionfor Townhouse Buildings Class 1aDesign and construction guide for BCA compliant sound and fire-rated construction

Timber-framed Construction

04


Building with Timber in Bushfire-prone AreasBCA Compliant Design and Construction Guide

09


Timber FlooringDesign guide for installation

© 2012 Forest and Wood Products Australia Limited. All rights reserved.

ThesematerialsarepublishedunderthebrandWoodSolutionsbyFWPA.

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WoodSolutionsAustraliaisaregisteredbusinessdivisionofForestandWoodProductsAustraliaLimited.

Technical Design GuidesA growing suite of information, technical and training resources created to support the use of wood in the design and construction of buildings.

Topics include:

#01 Timber-framed Construction for Townhouse Buildings Class 1a

#02 Timber-framed Construction for Multi-residential Buildings Class 2, 3 & 9c

#03 Timber-framed Construction for Commercial Buildings Class 5, 6, 9a & 9b

#04 Building with Timber in Bushfi re-prone Areas

#05 Timber service life design - Design Guide for Durability

#06 Timber-framed Construction - Sacrifi cial Timber Construction Joint

#07 Plywood Box Beam Construction for Detached Housing

#08 Stairs, Balustrades and Handrails Class 1 Buildings - Construction

#09 Timber Flooring - Design Guide for Installation

#10 Timber Windows and Doors

#11 Noise Transport Corridor Design Guide

#12 Impact and Assessment of Moisture-affected, Timber-framed Construction

#13 Finishing Timber Externally

#14 Timber in Internal Design

#15 Building with Timber for Thermal Performance

#16 Massive Timber Construction SystemsCross-laminated Timber (CLT)

Other WoodSolutions PublicationsR-Values for Timber-framed Building Elements

To view all current titles or for more information visit woodsolutions.com.au

#09 • Timber Flooring Design Guide

Table of Contents Introduction 4

1. Timber Flooring and Floor Finishes 6

1.1 MovementinTimberFloors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

1.2 TimberSpeciesandCharacteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

1.3 FloorsOverDifferentSub-Floors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

1.4 FloorFinishTypesandCharacteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

2. Pre-Installation Requirements 13

2.1 StorageandHandlingProcedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

2.2 TimberFlooringStandardsandSpecifications. . . . . . . . . . . . . . . . . . . . . . . . . . .13

2.3 EvaluatingSiteConditionsandtheInstallationEnvironment . . . . . . . . . . . . . . . . . . .14

2.4 ConsideringtheLikelyMovementAfterInstallation . . . . . . . . . . . . . . . . . . . . . . . .17

2.5 InstallationMoistureContentandAcclimatisation. . . . . . . . . . . . . . . . . . . . . . . . .17

3. Installation to Timber and Sheet Sub-Floors 19

3.1 Sub-FloorVentilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

3.2 AssessingFixingRequirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

3.3 AllowanceforExpansioninFloors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

3.4 FloorLayingPractices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

3.5 InstallationofStripFlooringDirecttoJoists . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

3.6 InstallationofStripFlooringoverExistingTimberandSheetFloorsonJoists. . . . . . . . . . .25

3.7 InstallationofStripFlooringoverPlywoodandBattensonConcreteSlabs . . . . . . . . . . . .27

4. Installation by Direct Adhesive Fix to Slabs 32

4.1 AssessingandPreparingtheSlab. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32

4.2 MoistureVapourBarriers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33

4.3 Adhesives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34

4.4 DirectStickInstallationPractices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

5. Sanding and Finishing Timber Floors 38

5.1 AssessingtheFloorPriortoSanding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

5.2 PreparationforSanding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

5.3 Sanding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39

5.4 CoatingSystemApplication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42

6. Overall Appearance to be Expected 45

6.1 AcceptableAppearance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45

7. Care and Maintenance 49

7.1 ANewlyFinishedFloor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49

7.2 OngoingCareandMaintenance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49

Appendices

AppendixA–MoistureContentandTimberMovement. . . . . . . . . . . . . . . . . . . . . . . . .51

AppendixB–MeasuringMoistureContentofTimberandSheetProducts. . . . . . . . . . . . . . .55

AppendixC–SlabMoistureAssessment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .62

AppendixD–AcousticPerformance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65

AppendixE–UnderfloorHeating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68

AppendixF–InstallationChecklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72

AppendixG–TroubleshootingGuide. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .75


Introduction

Scope

This publication provides a reference guide for the installation of solid timber strip flooring over bearers and joists, timber-based sheet flooring products and concrete slabs. Generally, floors of this type are of solid timber or a laminated product made from layers of timber, bonded together. Flooring fits together with a tongue and groove joint. After the flooring is in place, the floor is sanded and finished. There are a number of other timber flooring products that are not of this type and are not covered by this guide. These include parquetry, pre-finished floors and ‘floating’ timber floor systems. When installing a strip timber floor, many aspects must be considered, including the house design, environment in which the floor is to be laid and the desired appearance of the finished floor. Such aspects influence the choice of species, cover width, fixings and finish to be applied. Information relating to product selection, assessing the installation environment, floor installation, sanding and finishing are provided in the guide, together with additional information of importance to the floor installer, sander and finisher.

The Flooring Process

Striptimberflooringisavailableinawiderangeofspeciesandcolours,fromharderandsoftertimbersandavarietyofprofilesandcoverwidths.Priortothefinishedfloorbeinghandedover,thereareanumberofprocessesthatmustbecorrectlyundertakentoachieveafloorwiththeperformanceandappearancethatisofaprofessionalstandard.Eachstagegenerallyinvolvesdifferentsectorsoftheindustry,eachhavingspecificskills.Eachstageisofequalimportance,withdefinedresponsibilities.Alackofattentionatanyparticularstagecanadverselyaffectthefinishedfloor.Thestagesareasfollows:

• Manufacture–Usuallycarriedoutbyasawmiller,however,driedroughsawnboardsmaybemachinedintofinishedfloorboardsundertakenbyaseparateoperation.

• Distribution–Flooringisoftensoldtotimbermerchantswhoon-selltotheinstaller.

• Specification–Architects,designersandownersusuallyspecifytheproducttobeinstalled.

• Sub-floor–Buildersprovidethejoistsandbearersorslaboverwhichafloorislaid.

• Installation–Specialistfloorinstallersandcarpentersinstallfloorsoverthesub-floor.

• SandingandFinishing–Generallyundertakenbyprofessionalfloorsandersandfinishers.

Selective logging from sustainable managed forests often starts the process.


The Owner’s Choice

Aspectsrelatingtowhatcustomersdesireareofparamountimportanceandshouldnotbetakenlightly.Theyarerelyingontheexpertiseofthoseinthesixstagesoutlinedaboveandeachareacaninfluencetheowner’ssatisfactionwiththeirfloor.Eachfloorisuniqueandisoftenseenbytheownerasafocalpointoftheinteriordesign.Thoseselectingatimberfloorwilloftenchooseoncolour,withboardwidthinfluencinghowthenaturalcoloursareblended.Timberhardness,ormatchingtoanexistingfloor,canalsobeofprimeimportance.Aspectssuchastheoriginoftheflooringintermsofcountry,foresttypeorrecycled,canalsobeofimportancetotheowner.

Ownersaremoreawareandhavemoreaccesstoinformationthaneverbefore,howevertheyareunlikelytohavethesamedepthofknowledgeasthosedealingwithtimberflooringonaday-to-daybasis.Itisimportanttoaccommodatecustomerpreferences,howeverthisshouldnotbetothedetrimentoftheperformanceofthefloororitsfinalappearance.Wherecustomerpreferencescannotbeaccommodated,thisneedstobebroughttotheirattention.Wheretheirchoicescanbeaccommodatedbutmayaffecttheappearanceofthefloor,thenthistooneedstobebroughttotheirattentionandfollowedupinwriting.Colourvariationbetweenshowroomsamplesandtheproductprovided,provisionofexpansionjointsandhighlevelsofsunexposureonanareaofthefloorareallareasthataffectappearanceandmaynecessitatespecificdiscussionwiththeowner.

Left: The client’s wishes need to be accommodated but not at the expense of floor performance.

Right: Showrooms provide an excellent environment, where clients not only see many types of floors and finishes but where valuable information can be conveyed regarding floor systems, performance and care of timber floors.


1Timber Flooring and Floor Finishes

1.1 Movement in Timber Floors

Priortodiscussingtimberflooringproducts,itisimportanttounderstandtherelationshipbetweentimber,humidityintheairsurroundingitandthedimensionalchangesthatoccurastheresultofchangesinhumidity.Duringconsistentlyhighhumidityweather,timberwillabsorbmoisturefromthesurroundingaircausingittoswellorincreaseinsize.Conversely,duringdriertimeswhenhumiditiesarelow,timberwillshrink,reducinginsize.Unlesstongueandgroove(T&G)flooringisplacedinapermanentlycontrolledenvironment,itwillalwaysmoveinresponsetochangingenvironmentalconditions.GapsbetweenindividualT&Gboardswilloccurasthefloorshrinksindryweather.Similarly,duringeitherpersistentwetweatherorattimesofnaturallyhighhumidity,floorswilltendtobetightershowingfewerandsmallergaps.

Left: Cover width variation with changing relative humidity.Right: Small gaps at board edges may occur, particularly during dry weather.

A‘continuousmirrorfinish’cannotbeexpectedfromfloorfinishes.Localisedshrinkagemayalsooccurwhenareasofflooringareexposedtoheatsources,suchasfireplacesorsunlightthroughlargedoorsorwindows.Theoverallmovementandrateofmovementoftimbervariesdependingonthetimberspeciesandcuttingpatternofindividualboards.Smallmoisturecontentvariationsinboardsatthetimeofinstallationanddifferingconditionswithinthehouse(e.g.fromsunexposureorfireplaces)willalsocausevariationinboardmovement.

Consequently,gappingacrossafloorcanbeexpectedandmayberelativelyeven,dependingonindividualcircumstances,butactualgapsizebetweenindividualboardswillvary.Forthesamechangesinmoisturecontent,widerboardswillmovemorethannarrowerboards.Therefore,gapsinwideboardfloorsaregenerallywiderandmorenoticeable.Anunevendistributionofgapscandetractfromtheappearanceofthefloorandmayoccurifanumberofboardsarebondedtogetherbythefinishpenetratingintothejoints.Floorfinisheswillnotpreventtimbermovement,butmayreducetherateofresponsetoclimaticchanges.Applyingafinishtotheundersideofafloormayhelpreducetheimpactofsuddenchangesintheweather.

1.2 Timber Species and Characteristics

Species, colour, grade and hardness

Thespeciesorspeciesmixwillgenerallydeterminetheoverallcolourofthefloor.Mixesmaycontaindifferentspeciesfromoneproducertoanotherandmaythereforeappeardifferent.Evenwhenasinglespeciesischosentherecanbeawidevariationincolourandalimitednumberofboardsofadifferentspeciesmaybepresentduetosimilarityinappearance.Asaguide,Table1.1(page8)indicatestherangeofcoloursthatmaybeexpected.Thesapwoodofmanyhardwoodscanbemuchlighterthanadjacentheartwoodandsomeboardsmaycontainbothlightanddarkcolours.Evenwithinasinglespeciesandwithinindividualtrees,largecolourvariationscanoccur.


Theageofthetreecanhaveasignificantinfluenceonthecolour,withyoungertimberoftenbeinglighterthanmorematuretimber.Theproductsuppliedmaydifferincolourtoshowroomsamplesandthisshouldbediscussedwithflooringsuppliersandowners.Itisalsopreferablethatflooringissuppliedfromonemanufacturingsourceandthatthepacksareofasimilarage.

SomeStates,includingQueenslandandNewSouthWales,requirethelyctid-susceptiblesapwoodofsomehardwoodspecies(e.g.SpottedGum)tobepreservativetreated.Sometreatmentsmayimpartabrowntingetosapwood,whileboronpreservativeisnon-colouring.Lightorganicsolventpreservative(LOSP)treatmentisalsoused.InthisinstanceH3treatmentmaybeusedinlieuofH2treatmenttoavoidthecoloureddiesoftenusedwithH2LOSPtreatments.

Thecharacterofthefloorisinfluencedbythespeciescharacteristicsandthereforethegrade.Gradingisaprocessthatsortsboardsaccordingtothenumberandsizeoffeaturespresent(e.g.gumveinsandknots).ThefollowingtableindicatesthegradescontainedinrelevantAustralianStandards,butitshouldbenotedthatmanufacturersoftenhavetheirowngrades.Often,flooringthatcontainsmorefeaturesismoremoderatelypriced,however,irrespectiveofthefeaturespresent,thereisnodifferencebetweenthegradesintermsofmachiningtolerances,permittedmachiningimperfectionsandmoisturecontent.

Itisimportanttorealisethattheoverallcolourorblendofcolourinafloorisdependentonthespeciesorspeciesmixchosenandthecharacterofthefloor,intermsofthefeaturespresent,suchasgumveins,isdeterminedbythegrade.Ifchoosinganalternativespeciesfromtheoneoriginallyconsidered,notonlywilltheoverallcolourdifferbutthedominanttypeoffeaturemayalsochange.Itisimportantthatsuppliers,installersandclientsworkcloselytogethertoensurethatthedesiredlookoftheflooringisclearlyunderstoodbyall.

Hardnessindicatestheresistanceofaspeciestoindentationandabrasion.Damagetotimberfloorsmayoccurduetocontinualmovementoffurniture,heavyfoottrafficandinparticular‘stiletto-heel’typeloading.Theselectionofahardtimberspeciesensuresimprovedresistancetoindentationandabrasion.Softtimberspecies,ifusedinfeaturefloors,canbeexpectedtoindent.Floorfinisheswillnotsignificantlyimprovethehardnessoftimberflooring.Insomespecies,thehardnessofyoungergrowthmaterialcanalsobemuchlowerthanmaturetimberofthesamespecies,butthisvariesfromspeciestospecies.

Tasmanian Oak – Medium Feature Grade. Cypress – Grade 1.

Jarrah – Select Grade. Blackbutt – Select Grade.

#09 • Timber Flooring design guide

Table 1.1: Australian Hardwoods to AS 2796 – Timber, Hardwood, Sawn and Milled Products.

Select Grade, Medium Feature/Standard Grade and in some species High Feature Grade

Species Origin Colour Hardness Common Thickness(mm) coverwidths(mm)

HardwoodflooringspeciesgrowninQueenslandandNorthernNSW(may also be supplied as a mix of similar colour)

Spotted Gum (Corymbia citriodora) Qld, NSW brown, dark brown, very hard 60, 80, 85, 130, 180 19, 12, 13, 14(Corymbia maculata) light sapwood

Blackbutt (Eucalyptus pilularis) Qld ,NSW golden yellow to pale brown very hard 60, 80, 85, 130, 180 19, 12, 13, 14

White Mahogany (Eucalyptus acmenioides) Qld, NSW pale yellow-brown very hard 60, 80, 130 19, 12

Grey Ironbark (Eucalyptus siderophloia) Qld, NSW dark brown or dark red-brown very hard 60, 80, 85, 130, 180 19, 12, 13, 14

(Eucalyptus paniculata) light sapwood

Red Ironbark (Eucalyptus crebra and fibrosa)

(Eucalyptus sideroxylon) Qld, NSW dark brown or dark red-brown very hard 60, 80, 130 19, 12, 14

Rose Gum (Eucalyptus grandis) Qld , NSW straw pink to light red-brown hard 60, 80, 85, 130 19, 12, 13, 14

Brushbox (Lophostemon confertus) Qld , NSW mid red-brown even colour hard 60, 80, 85, 130 19, 12, 14

Tallowwood (Eucalyptus microcories) Qld , NSW greyish yellow, olive green hard 60, 80, 85, 130 19, 12, 13

Turpentine (Syncarpia glomulifera) Qld , NSW pale reddish brown very hard 60, 80, 85, 130 19, 12

Forest Red Gum (Eucalyptus tereticornis) Qld dark brown or dark red-brown very hard 60, 80, 85, 130 19, 12, 14

Gympie Messmate (Eucalyptus cloeziana) Qld yellow brown very hard 60, 80, 130 19

New England Blackbutt (Eucalyptus andrewsii) NSW straw to pale brown very hard 60, 80, 85, 130 19, 12, 13, 14

Sydney Blue Gum (Eucalyptus saligna) NSW straw pink to light red-brown hard 60, 80, 85, 130, 180 19, 12, 13, 14

Manna Gum (Eucalyptus viminalis) NSW pale straw pinks mod. hard 60, 80, 130 19, 12

HardwoodflooringspeciesgrowninVictoria,SouthernNSWandTasmania

Victorian Ash (Eucalyptus regnans, Vic pale pink to yellow-brown mod. hard 63, 68, 80, 85, 108, 12, 14, 19, 20, 21E.delegatensis) 133, 160, 180

Tasmanian Oak (Eucalyptus regnans, Tas pale straw to light brown mod. hard 60, 65, 85, 108, 133, 10, 12, 13, 14, 19, E. oblique, E. delegatensis) 160, 180, 85, 112 20, 21

Messmate (Eucalyptus oblique) Tas pale straw to light brown mod. hard 60, 68, 85, 108, 10, 12, 13, 14, 19 112, 133

Mountain Ash (Eucalyptus regnans) Vic, Tas pale straw to light brown mod. hard 60, 63, 68, 80, 85, 12, 13, 14, 19 108, 112, 133

Alpine Ash (Eucalyptus delegatensis) Vic, Tas pale straw to light brown mod. hard 60, 63, 68, 80, 85, 12, 13, 14, 19 108, 112, 133

Southern Blue Gum (Eucalyptus globulus) Vic, Tas pale brown with some pink very hard 60, 63, 80, 85, 108, 12, 13, 19 112, 133

River Red Gum (Eucalyptus camaldulenis) Vic rich deep reds hard 63, 80, 85, 108, 133 12, 19

Yellow Stringybark (Eucalyptus muelleriana) Vic even, yellow-brown hard 63, 80, 85, 108, 133 12, 19

Manna Gum (Eucalyptus viminalis) Vic pale straw pinks mod. hard 63, 80, 85, 108, 133 12, 19

Shining Gum (Eucalyptus nitens) Vic pale brown some pinks mod. hard 63, 80, 85, 108, 133 12, 19

Myrtle (Nothofagus cunninghamii) Tas straw & light pink, mod. hard 60, 65, 85, 108, 13, 19 light sapwood 112, 133

Blackwood (Acacia melanoxylon) Tas light golden to deep brown mod. hard 60, 65, 85, 108, 13, 19 112, 133

HardwoodflooringspeciesgrowninWesternAustralia

Jarrah (Eucalyptus marignata) WA rich reddish-browns hard 80, 85, 105, 125, 130 12, 13, 19 to soft salmon pinksKarri (Eucalyptus diversicolor) WA rich reddish-browns hard 80, 85, 125, 130 12, 13, 19 to pale pinks

#09 • Timber Flooring design guide

Species Origin Colour Hardness Common Thickness(mm) coverwidths(mm)

CypresstoAS1810–Timber,seasonedCypress,milledproductsGrades No.1 and No. 2

Cypress (White) (Callitrus glaucophylla) Qld , NSW pale straw sapwood, mod. hard 62, 85 20

dark brown heartwood

AustralianSoftwoodstoAS4785–Timber,softwood,sawnandmilledproductsexceptAraucaria(HoopPine)forwhichindustrygradesapplyStandard Grade for AS 4785

Araucaria (Hoop) (Araucaria cunninghamii) Qld , NSW light straw soft 87, 89, 102,1 33, 152 19, 20, 21

Radiata (Pinus radiata) Vic, NSW, straw soft 104 19, 21 SA, WA

AustralianSoftwoodsImportedHardwoodstoAS2796–Timber,hardwood,sawnandmilledproductsSelect Grade, Medium Feature / Standard Grade and in some species High Feature Grade

Kwila / Merbau (Instsia bijuga) S.E. Asia dark brown hard 80, 130 19

Northern Box (Tristania obovata) S.E. Asia mid brown even colour hard 80, 130 19

Maple (Rock or Sugar) (Acer saccharum) Nth. America light straw mod. hard 50, 57, 83 19

Note: Not all species, width and thickness combinations are available. Check with suppliers before specifying.

Cover widths, profi les, spans and end-matching

TypicalcoverwidthsandthicknessesforT&Gstripflooringareasshowninthetableabove.Actualcoverwidthsmayvaryfromthoseshownandshouldbecheckedwithindividualsuppliers.TypicalT&Gprofilesareshowninthefigurebelow.Someprofilesareproducedwithgroovesorrebatesontheunderside.Wheretheundersideofafloorformsaceiling,theboardedgesmaybearrisedtoforma‘V’jointprofile.Bothprofilesareusedfortop(face)nailingandsecretfixing.The‘standardprofile’ismorecommonlyfoundonwiderboardsandsomemanufacturersindicatethatsuchboardsshouldbetop(face)nailed.Somewiderboardflooringhasthesecretnailprofilewhichallowstemporarysecretfixingpriortotop(face)nailing.

Ifthespeciesorspeciesmixcontainsasignificantvariationincolourstheappearanceofthefloorwilldifferdependingonthecoverwidth.Narrowerboardstendtoblendthecolourvariationstogether.Gappingbetweenindividualboardsduringdriertimesisalsolesswithnarrowerboardsthanitiswithwideboards.Aboardwidthof100mmorlesswilllimitpotentialgapsizeandothermovementeffectssuchascupping(edgesoftheboardhigherorlowerthanthecentre).Ifwiderflooringisusedthenwidergappingcanbeexpectedandundercertainconditionssomecuppingbecomesmorelikely.

End-matchingisaprocesswhereaT&Gjointisprovidedattheendsofboards.Themajorityofflooringisnowend-matched.Forfloorslaiddirecttojoistsorbattensthisallowsjointstobeplacedbetweenthejoistorbatten,resultinginlesswastagethanplainendflooring,whichmusthaveitsendsfixedoverthejoistorbatten.

Plain End End-matched


Floor lengths

Flooringisgenerallysuppliedinrandomlengthpacksupto4.8minlength.Theaveragelengthisoftenbetween1.8mand2.1m.Packsofshorteroveralllengtharealsoavailablefromsomesupplierstofacilitatefloorsinhigh-risebuildingsthatrequireproducttobetakentotheappropriatefloorbylift.Theminimumlengthfortimberbeingfixedtojoistsis900mm,basedona450mmjoistspacing.Insomeinstances,ifitisknownthatthefloorwillbelaidoverastructuralsub-floor,thenlengthsshorterthat900mmmaybeprovided.

Ordering flooring

Whenorderingtimberflooring,thefollowingdetailsshouldbeprovidedtothetimbersupplier:

• species(orspeciesmix)

• grade

• profileandend-jointtype

• coverwidth

• thickness

• quantity(inlinearmetres)

Flooringisgenerallysuppliedwithinthemoisturecontentrangefrom9%to14%.Forlargerjobsinspecificenvironmentsadifferentrangemaybespecified.

Tocalculatethelinearmetresofflooringrequired,thefollowingmethodisrecommended:

Totallengthofflooringrequired=Areaoffloor(m2)x1000+Wastage Coverwidth(mm)

Allowanceforwasteshouldbeapproximately5%forend-matchedflooringand10%forplainendbutt-joinedflooring.

1.3 Floors Over Different Sub-Floors

DependingontheT&Gsub-floorsupportingsystem(e.g.joists,plywoodonslabetc),timberfloorswillbothfeelandsounddifferentlywhenwalkedon.GenerallyT&Gtimberfloorslaidoverjoistsorbattenswillhavemorespringunderfootandthereislikelytobesomeverticalmovementatboardedgesandend-matchedjointswhenwalkedon.Somesqueakscanthereforebeexpectedfrommosttimberfloorsofthistype.Squeakscanoccurfrommovementofoneboardedgeagainstanotherorfromboardsmovingonnails.Squeaksareoftenmoreprevalentduringdrierweatherduetolooseningatthejoints.Floorsthatarelaidoverplywoodonaslabwillhaveafirmerfeelunderfootandsomeareasmaysounddrummy.Similarly,whenfloorsareglueddirectlytoconcretethefeelisfirmer,andagainsomeboardsmaysound‘drummy’whenwalkedon.

Incoolerclimates,slabheatingmaybepresent.Duetothedirectheatingeffectonthetimberandintermittentusethroughouttheyear,substantialseasonalmovementcanbeexpected.Althoughstripflooringcanbeused,ifcareistakenwithappropriateproductselectionandinstallationpractices(refertoAppendixE–UnderfloorHeating),itmaybepreferabletouseengineeredtimberflooringproductswherelessdimensionalchangeswouldbeexpected.Evenwiththeseproductscareisstillnecessary.

1.4 Floor Finish Types and Characteristics

Timberfloorfinishescanbegroupedintofourmaincategories:penetratingoilsandwaxes,curingoilsandalkyds,oilmodifiedurethanes,andpolyurethanes.Thelatterthreecategoriesareavailableinsolventborneandwaterborne.Thepolyurethanesarealsoavailableinyellowing(aromatic)andnon-yellowing(aliphatic)types.AllfourcategoriesareavailableinlowtohighVOC–volatileorganic(solvent)content.Glossleveloptionscanrangefromveryhighglosstomatt.

Performanceparameterssuchasdurabilitycanvarysignificantlywithinacategoryaswellasbetweencategories.Allcategoriescanberecoatedwithrefurbishmentcoats.Thedegreeofsurfacepreparationrequiredpriortorecoatingwillvarywithtimeandcoatingtype.

Penetrating oils and waxes

Theseareblendsofnaturaloilsandwaxeswithaddedchemicalsalt‘driers’.Theyaredissolvedintospirittypesolvents,withsomeoftheverylowvolatilityonesmeetingtheGreenBuildingCouncilofAustraliaguidelinesof140g/LVOCemission.Thiscoatingtypecanhavehighmaintenancerequirementsnecessitatingregularapplicationofmetalisedacrylicpolishes.


However,itisthenaturallookofthecoatedtimberthatisoftenthebasisofselection.Thesetypesofcoatingswilldarkensignificantlyonageingandareslowtocureincoldweather.Currentlytheydonotformalargepartofthefloorfinishmarket.

Oil-based finishes – curing oils and alkyds

Curingoilssuchas‘tung’or‘linseed’,dissolvedinmineralturpentineorwhitespirits,containaddedchemicalcuringagentscalledmetaldriers.Theyareusuallyselectedbecausetheyarelowcost,havegoodedgebondingresistanceandproducearichtimbercolour.Theycanbeveryslowcuringincoldweatheranddarkensignificantlywithage.Sometypescanalsoyellowinthedarkorwhencovered.Durabilityislowcomparedtotheothercoatingtypesandtheyrequirefrequentmaintenancewithuseofmetalisedacrylicpolishes.Glosslevelsvaryfromhighglosstosatinandtheyhavegoodedgebondingresistance.

Alkydsareproducedfromreactingcuringoilswithsyntheticresinanddissolvingintospirit-basedsolvents.Thisresultsindurabilitybeingimprovedfromalowtoamoderatelevel.Maintenancerequirementsareconsideredtobeofamediumlevel.Again,thisisalower-costoptionwhencomparedtothemoredurableoptionsfollowing,providinggoodedgebondingresistanceandarichtimbercolour.Thesemoretraditionaltypesoffinishesarenotascommonlyusedasthoseoutlinedbelow.

Oil modified urethanes (OMUs)

Thesespirit-basedsolventbornecoatingscombineanoilwithasmalleramountofaurethane.Thehighertheurethaneproportion,thelesstheoilproperties,suchashigherflexibilityandresistancetoedgebonding.Conversely,thehighertheurethanecontent,thehigherthedurabilityandthelesstheflexibility.Glosslevelsvaryfromhighglosstosatin.Inrecenttimes,waterborneOMUshaveappearedonthemarket.Althoughofhighercostthanthesolventborne,thewaterborneOMUshavetheadvantageoflowVOCemissions.

AllOMUsyellowsignificantlywithageandtheirslowcuringincoldweathermustbeconsidered.Thesecoatingsareoftenselectedduetotheirintermediatecost,beingisocyanatefree,havinggoodedgebondingresistanceandbeingofintermediatedurability.

Essentiallytheyrepresentacoatingthatisreasonablydurableandgenerallyfreefrompotentialconcernssuchasedgebonding.Theyholdamoderateshareofthemarket.

Polyurethane – solventborne

Thiscoatingtypeprovidesthehighestdurabilityandfilmbuild(%solids)ofallcoatingtypesaswellasthehighestglosslevelsfortheglossoptions.However,thereisastrongsolventsmellonapplicationandtheyarealsoofhighesttoxicity(isocyanatecontent)untilthecoatinghascured.Thisismoresowithtwopackthantheonepackmoisturecure(MC)variety.Withthecorrectuseofpersonalprotectiveequipmentthisaspectisnotconsideredanissue.Thereareyellowing(aromatic)andnon-yellowing(aliphatic)varieties,withfurtheroptionsofhighsolids,andglosslevelsfromultrahighglosstomatt.

Thesecoatingsareoftenselectedastheyprovidethebestwearresistanceordurability,resultinginlowermaintenance.Theycanbeusedwithfastdrysealers,providethehighestglossandfilmbuildoption,areofintermediatecostandgenerallyprovidetrouble-freeapplication.Theydo,however,havepooreredgebondingresistance.ThistypeoffinishiscommoninAustralia.

Oil modified urethane. Single pack solvent-based polyurethane.

#09 • Timber Flooring Design Guide Page 12

Polyurethane – waterborne

Thishasthewidestselectionofsub-categorieswithacrylic–polyurethaneblends,co-polymerurethaneacrylates,100%polyurethaneresins,bothyellowingandnon-yellowingtypes,andblendsofalltheprevious,withandwithoutwaxorsiliconewearadditives.Asaresult,thereisaspreadofpropertiesincludingwearresistancefrompoortoarguablyasgoodassolventbornepolyurethane.Greatercareisnecessaryinselection.Thosewithoutacrylicprovidebetterwearresistance.Theyareavailableinoneandtwopackoptions,thelatterutilisingeitheralowertoxicityhardeneroramoretoxiccrosslinker,whichisaconsiderationatthetimeofmixing.Mattthroughtoglossfinishesareavailableandthesefinishesgenerallydarkenlesswithtime.

Thesecoatingsareoftenselectedasahealthieroptionforbothcontractorandoccupierduetotheabsenceofanystrongsolventsmellsonapplication.

Theyprovidegoodedgebondingresistance.However,theyhavethehighestproductcost,canprovidealightertimberappearancedependingonthesealerandproductsused,andhaveahigherchanceoftanninstainapplicationmarks.Rapidshrinkageinthefloorandtheassociatedstretchingofthefinishatboardjointshas,onoccasions,causedtheappearanceoflight-colouredlinesatboardjoints.Thesefinisheshavedevelopedsignificantlyoverrecentyearsandtheirmarketshareismoderateandincreasing.

Waterborne polyurethane applied.

Thefollowingtableoutlinesthetypesoffinishavailableandlistsvariouspropertiesofeach.

Table 1.2: Timber Floor Coatings Selection Chart.

Property Penetrating Oilbased OMU Polyurethane oil/wax finishes Solventborne Waterborne

1pack 2pack 1pack 2pack

Wear resistance Low Low-Med Medium Very High Very High Med-High Med-VH

Ability of the floor to accept Low Low Medium Medium High Medium High careful foot traffic 3 days after coating. (Av. temp. 20°C)

Timber colour ‘richness’ Low-High High High High High Low-Med Low-Med

Resistance of the coating Low Low Low Low-High Low-High Med-High Med-High to yellowing with age

Ability to cure in cold/dry weather Low Low Medium Medium High Medium High

Ability to cure in Low Low Low Medium High Low Low cold and damp weather

Edge bonding resistance High High Med-High Low-Med Low High Med-High

Rejection resistance High Medium Medium Low-Med Low-Med Medium Medium

VOC emission at application Low-High High Med-High High High Low Low-Med

Inhalation hazard when Low Medium Medium High Very High Low-Med coating is applied

Odour on application Low-Med Medium Medium High Very High Low Low-Med

General product cost Med-High Low-Med Medium Medium Medium High Very High


Pre-Installation Requirements

2.1 Storage and Handling Procedures

Flooringshouldbedeliveredbythesupplierwithplasticwrapping(top,sidesandends)ingoodconditioninordertomaintaintheflooringattheappropriatemoisturecontent.Itisthefloorinstaller’sresponsibilitytocheckthatthetimberisattheappropriatemoisturecontentatthetimeofinstallation,soflooringproductsmustbeprotectedfromweatherexposureandothersourcesofdampness.

Ideally,deliveryduringrainshouldbeavoidedandflooringshouldnotbedeliveredtothesiteuntilitcanbeimmediatelystoredunderpermanentcover.Ifthisisnotachievable,otherprecautionsthatareequallyeffectivetopreventmoistureuptakeandexcessivesunexposurewillbeneeded.

Plasticwrappingiseasilydamagedandshouldnotbereliedupontokeeptheflooringdry.Ifmoisturepenetratestheplasticortimberisstoredoveramoistsurface,subsequentmoistureuptakecanresultinsignificantswellingofsomeboards.Flooringshouldnotbelaidinthiscondition,aswidegapsatboardedgesmayresultasboardsre-dry.Wrappedpacksshouldalsobeprotectedfromexcessivesunexposureasthistoocanhaveadetrimentaleffect.

2.2 Timber Flooring Standards and Specifi cations

Whentimberflooringisreceivedonsiteitshouldgenerallymeetthefollowingrequirements:• Grade–flooringtobesuppliedtothespecifiedgrade,whichmaybeamanufacturer’sgrade.Note

thatifamanufacturerhasgivenaspecificnametoagrade,theproductmaybesimilartooneofthegradescontainedwithinanAustralianStandardbutitislikelytodifferinsomerespects.Thismayormaynotbeimportanttocustomersandshouldberesolvedpriortosupply.

• Moisturecontent–shouldbeintherangeof9%to14%(10to15%forCypress)withtheaveragemoisturecontentforallpiecesapproximately11%(12%forCypress).

• Timbermoisturecontentsshouldbechecked.(Resistancemoisturemeterreadingsmustbecorrectedforspeciesandtemperature,andmaybeaffectedbyotherfactors.Correctedreadingsareapproximateonly.Ifindoubtconfirmresultsbyoven-drytests.)Watermarksorasignificantvariationincoverwidthwithinaboardmayindicatethatthetimberhasbeenmoistureaffected.

• Coverwidth–notmorethan1mmdifferencebetweenoneboardandanother.Coverwidthsshouldgenerallybewithin±0.5mmofthenominalcoverwidth.(Ifinexcessofthis,itcanreflectchangestoboarddimensionsthatcanoccuraftermillingandpriortoinstallation,andthereforebeoutsidethelimitsofAustralianStandards).

• Boardsshouldnotbevisiblycupped–AustralianStandardsallow1mmper100mmofboardwidth.

• Tongueandgroovetolerance–notlessthan0.3mmnorgreaterthan0.6mm.Boardsshouldslottogethertoforma‘snug’fit.Thefitshouldnotbelooseandsloppyoroverlytight.

• Undercutorrelief–thedifferencebetweentheupperandlowercoverwidthoftheboards.Generally,anundercutofabout0.5mmisappropriateforan80mmwideboardandalittlemoreasboardwidthincreases.Iftheundercutislargeandthereissignificantexpansionpressureafterinstallation,‘peaking’(pressure-relatedcupping)canoccur.Thesmallertheundercut,thelesstheeffect.

GradingrulesforsolidT&GstripflooringarecontainedinthefollowingAustralianStandards:

AS2796–Timber–Hardwood–SawnandmilledproductsAS1810–Timber–SeasonedCypresspine–MilledproductsAS4785–TimberSoftwood–SawnandmilledproductsAnyconcernsrelatingtothesespecificationsshouldbeaddressedpriortolayingthefloor.

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2.3 Evaluating Site Conditions and the Installation Environment

Evaluating site conditions

Everysiterequiresassessmentpriortotheinstallationofatimberfloor.Itisimportanttoknowtheclimateintheareawhereafloorisbeinglaid.Relativehumidityisthemajorinfluencedeterminingwhethertimberflooringwillabsorbmoisturefromtheairandswell,orlosemoisturetotheairandshrink.Ifthemoisturecontentofthetimberflooringisclosetotheaveragein-servicemoisturecontent,subsequentseasonalchangesinhumiditywillonlyresultinsmallchangesinmoisturecontent.Theclimatecanbeassessedfrom9amrelativehumiditydataavailablefromtheAustralianBureauofMeteorologywebsiteatwww.bom.gov.au/climate/averages.Thefigurebelowshowsannualrelativehumiditychartsassociatedwithatropicalclimate,temperateclimateandadryinlandclimate.Approximateaverageexternalequilibriummoisturecontents(EMC)arealsoprovidedonthegraphforeachclimate.Equilibriummoisturecontentcanbethoughtofasthemoisturecontentthattimberwillapproachundersetconditionsofrelativehumidityandtemperature.Itisevidentfromthesegraphsthattheclimatemayresultinmoisturecontentsthatcanbeeitherhigherorlowerthantheaveragemoisturecontentoftheflooringthathasbeensupplied.

RelativehumiditygraphsforthemajorcapitalsthroughoutAustraliaareprovidedinthefiguresbelow.Seasonalvariationabouttheaveragecanbeseentobegreaterinsomelocationsthanothers.Forexample,theseasonalvariationinSydneyismuchlowerthanMelbourne.Wheretherearegreaterseasonalvariations,greaterseasonalmovement(shrinkageandswelling)canalsobeexpected.

Climatic effects on timber floors – these must be considered when laying a floor.

Major centre climates and external EMCs.


TimberflooringisgenerallymanufacturedtosuittemperateclimateswithaverageexternalEMCsof12%to14%.Toprovideassistanceinassessingclimaticinfluencesthefollowingfigureoutlinesthegeneralrelationshipbetweentemperature,relativehumidityandmoisturecontent.AverageinternalEMCsaregenerallylowerthanexternalby1%to2%withoutheatingorcoolingsystemsoperatingandcanbe4%to5%lowerfortheperiodswhensuchsystemsareoperating.Therefore,inclimatesthathavecoldwinters,heatingsystemsoftenlowerthehumiditywithinthedwellingandreducetheeffectofhighexternalhumidityonthefloor.Similarly,intropicallocationsair-conditioningcanreducetheeffectofhighexternalhumidityonthefloor.Installationandfinishingpracticesneedtoaccommodateclimaticconditionsassociatedwithalocalityandtheseasonalmovementthatwilloccurinthatclimate.

Floors in moist environments

Inareasofhigherelevationthancoastalareas,averagemoisturecontentsareoftenhigherduetotheassociatedlocalweatherpatterns.Similarly,housesbuiltinbushysurroundingsorgulliesmayexperiencehigheraveragemoisturecontents.Moisterconditionsarealsooftenexperiencedwithhousesonfarmlandorinruralsettingsparticularlyincoastalandhinterlandareasexperiencinghigherormoreconsistentrainfall.Intheseareas,greaterallowanceforfloorexpansionisrequiredatthetimeofinstallation.

Relationship between temperature, relative humidity and EMC.

Higher levels of expansion are experienced in moist localities and must be accommodated.


Building and installation considerations

Closed in sub-floor space

Manydwellingsare‘brickedin’underneathandalackofsufficientventilationcanresultinhighhumiditiesinthesub-floorspace.Thismayresultinexpansionandcuppingoffloorboards.Quotedfiguresforsub-floorventilationarebasedonsub-floorspacesthatarenotsubjectedtoseepageorwhereventilationthroughthesub-floorspaceisinhibited.Wherehumidityremainsconstantlyhighbeneathafloor,coatingstotheundersideoftheboardswillnotreducethemoistureuptakeintotheflooring.Bushysurroundingsanddensegardensmayalsocausehighermoisturecontentsandreducedairflowthroughthesub-floorspace.

Houses with open sub-floors

Specialprecautionsmustbetakenwhentimberfloorsarelaidonjoistsinahousethatisopenunderneath,particularlywhenbuiltonsteeplyslopinglandorescarpments.Insuchlocations,verydrywindsorwind-blownrainorfogcandirectlyaffectthemoistureconditionofthelowersurfaceofthefloor.Thiscanresultineitherextremeshrinkageorextremeswelling.Inthelattercase,thefloormayliftoffthejoistsandstructuraldamagetothebuildingmayoccur.Also,wherethereislittlerestrictiontotheprevailingwind,floorscanreactmorerapidlytodrywinds.Thespeciesusedinthefloorandboardcoverwidthaffecttherateofmovementandshrinkage.Dependingontheseverityoftheexposure,optionstoprotectthefloorincludeprovidinganoil-basedsealertotheundersideofthefloor,whichmayprovideshortdurationprotectiontochangesinweather,andinstallingavapour-resistantliningtotheundersideofthejoistsorbuilding-intheunderfloorspace.

Internal environment

Withinadwelling,anumberofdifferingclimatescandevelop,causingareasofflooringtoresponddifferentlywithinthesamedwelling.Theclimateisinfluencedbylargeexpansesofglass,fireplaces,refrigerators,air-conditioners,appliancesthatventwarmair,theaspectofthehouseandtwo-storeyconstruction,allofwhichcanaffectthedimensionalmovementoffloorboards.Whenfloorsareexposedtothesunthroughlargeglassedareas,protectionshouldbeconsideredbefore,duringandafterconstruction.Evaporativecoolersaddmoisturetotheairandraisetherelativehumidity,andcanresultinhighermoisturecontentsintheflooring.

Araucaria (Hoop Pine) flooring and Araucaria floor framing

WhereAraucariafloorsandfloorframingarenotfullyencloseditisnecessarytosealtheframingmembersandlowersurfaceofthefloorboardstopreventattackfromtheQueenslandPineBeetle.AttackisspecifictotheAraucariaspecies(includingBunya)andgenerallyrestrictedtotheareafromBundabergtoMurwillumbahandeastoftheGreatDividingRange.Inthisregion,exposedframingandfloors(includingventilatedsub-floorspaces)requiresealingtomeetBCArequirements.Thesealerneedstohaveafilm-formingfinish,whichmayalsoreducetheeffectsofrapidweatherchanges.

Greater localised shrinkage and possibly some cupping can be expected with high sun exposure.

A dry sub-floor space and adequate ventilation is essential for good floor performance.


2.4 Considering the Likely Movement After Installation

Asdiscussed,timberisanaturalproductthatrespondstochangesinweatherconditions.Seasonalhumidityandtemperaturechangesintheaircauseboardstoshrinkandswellatdifferenttimesthroughouttheyear.

Theoverallmovementinindividualboardsandrateofmovementwilldependonthetimberspeciesandcuttingpattern.Smalldifferencesinmoisturecontentbetweenboardsatthetimeofmanufacture(a5%rangeisnormallyallowedbyapplicablestandards)andvariableconditionswithinthehouse(e.g.awest-facingroomcomparedtosouthfacing)willalsocausefurthervariationinboardwidth.Consequently,smallgapscanbeexpectedattheedgesofmostboards,particularlyduringthedriermonths,andtheactualgapsizesmaydifferacrossafloor.Incaseswhereshrinkageoccursafterinstallation,widerboards(e.g.130mm)willresultinlargergapsatboardedgesthannarrowerboards.Air-conditioninginstalledafterafloorhasbeenlaidmayincreasethesizeofshrinkagegapsatboardedges.

Somemovementusuallyoccursintimberfloorsafterlayingastheflooradjuststotheclimate.Althoughfloorfinishesmayretardmoisturecontentchanges,theywillnotpreventthismovement.Inapplicationswheregreatermovementisexpectedafterfinishing(e.g.fromseasonalchanges,useofwideboards,air-conditioninginstalledafterfloorinstallation),particularcareisnecessarytoensurethatthefinishdoesnotactasanadhesiveandbondanumberofadjacentboardstogether.Withsubsequentshrinkage,widegapsbetweengroupsoffourorfiveboardsmayoccurorboardsmaysplit.

Thewaydifferenttimberspeciesrespondinafloordependsnotonlyontheirmoisturecontentbutalsoontherateatwhichtheytakeupandlosemoisture,theassociatedmovementandtheirdensity.High-densityspeciesareextremelystrongandthosethattakeuporlosemoisturemorequickly(suchasBlackbutt)willalsofollowseasonalmoisturechangesmorecloselythanslowerrespondingspecies(suchasSpottedGum).Particularcareisnecessarytoaccommodateexpansionofthehigher-densityspecies.Inmoistlocalitiesthismaynecessitateprovidingsmallexpansiongapsevery6to10boardsduringinstallation,inadditiontonormalexpansionallowances.Lower-densityhardwoods(e.g.TasmanianOak,VictorianAsh)andsoftwoodswill,tosomeextent,compressattheiredgeswhenafloorexpands.Withthesetimbers,normalexpansionallowanceisgenerallyabletoaccommodatetheexpansioninmoistclimates.

2.5 Installation Moisture Content and Acclimatisation

Themoisturecontentoftimberisthepercentageweightofwaterinthetimbercomparedtotheweightoftimberwithallwaterremoved.Moisturecontentvarieswithchangesinthehumidityandtemperatureinthesurroundingair.Tominimisethemovementofafloor(swellingonmoistureuptake,shrinkageonmoistureloss)itisimportanttolayandfixtimberfloorsclosetotheaveragemoisturecontentoftimberintheenvironmentwhereitistobelaid.Alongcoastalareas,wherehigherhumiditiescanbeexpected,moisturecontentsofflooringmayvaryfrom9%to14%.Timberflooringisusuallysuppliedatanaveragemoisturecontentbetween10%and12.5%andmostboardscanbeexpectedtobewithinafewpercentoftheaverage.Whereconditionsaredrier,suchasinlandareasorinair-conditionedbuildings,averagemoisturecontentsofflooringmayvaryfrom7%to12%.Inthesesituations,flooringmayneedtobeacclimatisedon-site.

Edge bonding can result in wide irregularly-spaced gaps at board edges and split boards within the floor.


Wheretheaveragesuppliedmoisturecontentoftheflooringisneartheexpectedaveragein-servicemoisturecontent,acclimatisationisnotnecessary.

Inareaswherehigheraveragemoistureconditionspersistandwherefloorsareexpectedtohavehighermoisturecontents,additionalallowanceshouldbemadeforsubsequentexpansion.SuchareasincludetropicalnorthQueenslandandnorthernNewSouthWalesandareasofdensebushlandandrainforest,particularlyathigherelevationsandmountainareas.

Installationmethodstobeconsideredincludeeitherprovidingadditionalintermediateexpansionjointsoracclimatisingtheflooring.

Acclimatisingistheprocessofallowingpartialequalisationofthemoisturecontentofthetimberassuppliedtothatofthesurroundingsinwhichthetimberistobeinstalled.Increasingtheaveragemoisturecontentwillonlybeeffectiveifthehumidityintheairissufficienttocausemoistureuptake.Therateofmoistureuptakediffersfromspeciestospecies.Somehigher-densityspeciesareveryslowtotakeupmoisturefromtheair(e.g.SpottedGum)whileothersreactmorequickly(e.g.BlackbuttandBrushBox).IfflooringistobelaidinadryenvironmentsuchaswesternNewSouthWalesoraconsistentlyair-conditionedbuilding,thenacclimatisingcanbeeffectiveinreducingtheaveragemoisturecontentoftheflooringpriortolayingandtherebyreducinggapsizesatboardedgesfromboardshrinkage.Insuchclimates,futureexpansionofthefloormustbeallowedfortoaccommodateperiodsofwetweather.

Acclimatisingreliesoneachboardbeingexposedtothein-serviceatmospheresopacksmustatleastbeopenedupandrestackedinawaythatallowsairflowbetweeneachboard.Acclimatisingcanonlybeeffectiveinanair-conditionedbuildingiftheair-conditioningisoperatingatthetimeorindrylocalitiesduringdrierperiods.Thespeciesandperiodforwhichitisacclimatisedwillalsoinfluenceeffectiveness.Forsomehigher-densityspeciesthatareslowtoloseortakeupmoisture,acclimatisingmayhavelittleeffect.Acclimatisingindryclimatesdoesnotnegatetheneedtoprovideforfloorexpansionduringperiodsofwetweatherandwillnotovercomepoordryingpractices.

Asimpleguidetopre-installationconsiderationsisprovidedinthefigurebelowwhichshouldbereferredtoinconjunctionwiththeprecedingtext.

Acclimatisation can be effective if product moisture content and in-service conditions are known.


Installation to Timber and Sheet Sub-FloorsThis section outlines the recommended practices for laying timber strip floors over timber and engineered timber joists (it does not include steel joists), structural sub-floors such as plywood, particleboard and over concrete, but does not include direct adhesive fix to slabs (refer to Section 4).

When laying a timber strip floor over joists, either directly on the joists or on sheet flooring fixed to joists, adequate sub-floor ventilation is essential for the satisfactory performance of the floor. Sub-floor ventilation recommendations are therefore included in this section.

3.1 Sub-Floor Ventilation

Whenthelowersurfaceoftimberfloorsorstructuralsub-floors(overwhichatimberfloorislaid)areexposedtothegroundandthespaceisenclosed(bybrickworketc),thesub-floorspacemustbeadequatelyventilatedwithpermanentventsinstalledinthemasonryduringconstruction.Thehumidityinanenclosedsub-floorspacecanhaveaprofoundeffectontheperformanceofafloor.Ifconditionsareverymoist,thelowersurfaceoftheboardsmaytakeupmoisture,causingsubstantialswelling.Differentialmovementbetweentheupperandlowersurfacesoffloorboardsmayalsocauseboardstocup.Similarly,cautionneedstobeexercisedwithtimberfloorslaidinareaswherethemicroclimateisoftenmoist.Insuchlocationsthefloormayreachhighermoisturecontentsthaninothernearbyareasandadditionalallowanceforexpansionofthefloormayberequired(ReferSection2–Pre-installationRequirements).Timberfloorsshouldnotbelaidovermoistsub-floorspaces,andstructuralsub-floors(e.g.plywood)cannotbereliedupontopreventmoistureuptakeintheT&Gflooringifhumiditiesinthesub-floorspaceremainhighforextendedperiods.

Ventilation requirements

T&Gfloorsshouldbeprovidedwithsub-floorventilationthatexceedsminimumBuildingCodeofAustralia(BCA)requirements.TheBCAlevels(currentlylimitedto6000mm²permetrelengthofwallforhigherhumidityareas)areprimarilytolimitthemoisturecontentofsub-floorframingtimbers,whichcangenerallytolerategreaterfluctuationsinmoisturecontent,thantimberfloors.TherecommendedminimumventilationforT&Gtimberfloorsis7500mm2permetrelengthofwall,withventsevenlyspacedtoensurethatcrossventilationisprovidedtoallsub-floorareas(seefigurebelow).

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Adequate sub-floor ventilation and a dry sub-floor space are a must for timber floor performance.


Insomelocalities,tomeetconstraintsassociatedwithenergyefficiency,itmaybedecidedtoreduceventilationlevelstothevaluesprovidedintheBCA.TheBCAalsooutlinesthatamoisturebarrieroverthesoilbeneaththebuildingreducesventilationrequirementsandthisapproachisequallyapplicabletotimberfloors.Ifventilationisbelowtherecommendedlevel,dueconsiderationshouldbegiventoalternativemeasuresasoutlinedabove.Particularattentionshouldbepaidtoensuringthatthesub-floorspaceremainsdrythroughoutallseasons.Thetypeofventmayalsoneedtobeconsideredasinbushfireareasthemeshsizeusedinventsislimited.Somecommerciallyavailableventsofvarioustypes,theirdimensions,netventilationareaandrequiredspacingforcoastalZone3isprovidedbelow.BCArelativehumidityzonesandassociatedBCAventilationrequirementsarealsoprovidedbelow.Themaximumventspacingirrespectiveofnetventilationareais2mandanyscreensthatmaybenecessaryinbushfireareasorforverminproofingmayrestrictairflowandthismayneedtobecompensatedfor.

Ventilation efficiency and site drainage

Thesub-floorspacemustbefreefromallbuildingdebrisandvegetation.Obstaclesthatpreventairflowtoandfromventswillreducetheefficiencyofthesub-floorventilationsystem.Landscapingaroundtheexternalperimeterofthesub-floorspaceandstructuralelementsshouldnotlimitairflow.Ventsshouldbeinstalledinthemasonrycoursebelowfloorbearers,andshouldnotbeobscuredbyengagedpiersorpiers/stumps/columns,orbyanyservices.Whereexternalstructures(fences,etc)orlandscapemayreduceairflow,considerationshouldbegiventotheuseofmorethantheminimumnumberofvents.

Whereverandahsordecksareconstructedoutsidethedwellingperimeter,careshouldbetakentoensurethattheamountofventilationprovidedaroundtheverandahordeckperimeterisequivalenttoorgreaterthantheamountrequiredfortheadjacentexternalwall.Whereventilationisobstructedbypatios,etc,additionalventilationshouldbeprovidedtoensurethattheoveralllevelofventilationismaintainedandcrossflowisachieved.

Ifadequatenaturalventilationcannotbeprovidedtosub-floorspaces,amechanicalventilationsystemshouldbeinstalledwhichreplacesalltheairinthisspaceonaregularbasisandpreventstheformationof‘dead-air’pockets.


Iftherearedoubtsoverthesub-floorhumidity(areasofhighwatertable,reducedairflowduetominimumclearancesbetweenthesub-floorframingandground,externalstructures,etc)againapolyethylenemembranelaidoverthesoilshouldbeconsidered(tapedatjointsandfixedtostumpsandwalls).Asdiscussedabove,thiscansignificantlyreducemoistureuptakebythesub-floorair.Increasedlevelsofventilationshouldalsobeconsideredinsuchinstances.Withdwellingsonslopingblocksthathaveenclosedsub-floorspaces,thepossibilityofseepageshouldbetakenintoconsiderationandappropriatecontrolmeasurestakenpriortotheinstallationofthefloor.

Thedrainagesystemprovidedtothedwellingsite,shouldensurethatrun-offwaterwilldrainawayfromthebuildingperimeter(nottowardsit)andthatrun-offwaterispreventedfromenteringthesub-floorspace.Thegroundbeneathasuspendedfloorshouldalsobegradedsothatnopondingispossible.Wherespringsoraquifersarepresent(e.g.exposedbyearthworksonslopingsites)andcausewatertoenterthesub-floorspace,acloseddrainagesystemshouldbeinstalledunderthedwellingtoremovethiswater.Theventilationsystemwillnotcopewiththislevelofmoistureinthesub-floorspace.

3.2 Assessing Fixing Requirements

Duetoclimaticdifferencesthefixingrequirementsofthefloorneedtobecarefullyassessed.Applicablefixingrequirementsdiffertosomedegreebetweenstatesandbetweenlocationswithineachstate.

Top(face)nailingisamorerobustfixingmethodthan,say,floorssecretlyfixedwithbeadsofadhesive.Top(face)nailedfloorscanaccommodategreatermovementandexpansionpressurewithoutbuckling.Increasingtheamountofadhesiveusedwillalsoprovideamorerobustfixingandsomeinstallerselecttobondthefloorwithafullbedofadhesive.Wheregreaterfloorexpansionisexpectedafterinstallation,considerthemethodoffixingchosenandassociatedspacingoffixingsoramountofadhesive.Afullbedofadhesiveinhumidlocalitieswilllimitfloorexpansionbutcanalsocontributetohigherpressureatboardedgesmakingthefloormorepronetopeaking,resultinginacuppedappearanceandattimestentingofboards(refertoAppendixG–TroubleshootingGuideforexplanationofterms).

Itshouldalsobenotedthatthespecifiedrecommendationsinthismanualaregenericinnatureand,althoughfrequentlyused,installerswithknowledgeandexperienceinaparticularlocalitymayfixafloorinamannerthatdiffersfromthatoutlinedhere.Therearealsoanincreasingnumberofflooringmanufacturerswhoareproducingspecificproductswithaccompanyinginstallationinstructionsandsuchinstructionsshouldbestrictlyfollowed.Thisincludeswiderthinoverlayboardsandstandardprofileflooringforsecretfixing.Othermanufacturersrecommendthatstandardprofileflooringshouldnotbesecretlyfixed.Itshouldberecognisedthatspecificmanufacturingmethodsmayapplytocertainproducts,similarlookingproductsofdifferentmanufacturemaynotperformequivalentlyevenwiththesamefixingmethod.

TheinstallationmethodscoveredbythismanualareusedextensivelybymanyinstallersthroughoutAustraliaandformthebasisfortheindustry’srecommendations.


3.3 Allowance for Expansion in Floors

Fittedfloorsrequireaminimum10mmexpansiongapbetweenthefloorboardsandanyinternalorexternalwallstructures.However,whereboardendsabutdoorways,thegapmaybereducedtoaneatfitbutwithasmallgap(approximately1mm)topreventrubbing.Floorsupto6mwide(measuredatrightanglestotherunofboards)shouldnotrequireintermediateexpansionjointsprovidedthatitisanormalin-serviceenvironment(refertofigurebelow).Forfloorwidthsover6morwhereextraallowanceforexpansionisrequired(e.g.moistlocations)crampingpressureneedstobeconsideredaswellasprovidinganintermediateexpansionjointoraseriesofsmallerexpansiongapsevery800mmto1000mmtoprovideequivalentspacing.Ifcorkexpansionjointsareused,thecorkshouldbe2mmorsoproudofthefloorsurfacewheninstalled.Thiswillberemovedduringthesandingprocess.Corktotheperimetershouldbeinstalledlevelwiththetimbersurface.Itshouldbenotedthatcorktoaluminiumdoorjoinerycancausethejoinerytobowunderfloorexpansionandanaluminumangleasshowninthediagrambelowovercomesthis.Thisanglemayalsobeinvertedandadhesivefixedtothealuminiumjoinery.Alternatively,asmalltimberbullnosemouldingonflatfixedtotheflooringcanbeused.

3.4 Floor Laying Practices

Themoisturecontent,sizeandprofileoftheflooringshouldbechecked(Section2–Pre-installationassessment)priortolaying.Ifthemoisturecontentisnotcorrectortheboardsdonotfittogetherproperly,orareotherwiseconsideredtonotmeetthespecifiedgrade,theinstallershouldcontactthesuppliertoresolvetheseissuesbeforecommencinglaying.Similarly,anyboardfoundduringlayingthatisconsideredoutsidethegradespecificationshouldnotbelaid.

Top(face)nailingistobeundertakenuniformlywithrespecttoedgedistancesandalignmentacrossthefloor.Somevariationduetobattenandjoistlayoutmayoccur.

Cork intermediate expansion joints blend in well with timber fl oors.

Particularly for wide fl oors or in moist climates small regular gaps can be used to provide the additional expansion allowance needed. These often close during humid periods.


Whenlayingoverastructuralsub-floorsuchasplywoodorparticleboarditisimportantthatthefixingisadequate.Inmoderatelyhumidlocationsithasbeenfoundthatnailandadhesivefixedsheetflooringhasinsomeinstancesbuckledoffthejoists,evenwhenfixedinaccordancewiththerelevantnailingrequirementsofAustralianstandards.Screwfixingtothejoistsasoftenusedprovidesforamorerobustfixing.

Whenlayingoversheetflooringoranexistingfloor,boardsshouldbestaggeredtoprovidethelookofafloorsimilartothatlaidoverjoists.Itisgoodpracticetoensurethatendjointsareatleast450mmapartandthatjointsdonotclustertogetheroralign.Foraestheticreasons,closealignmentofendjointsinadjacentboardsshouldgenerallybeavoided.

Installersshouldconsiderhowtheboardswillbedistributedinthefloorintermsoflength,grade,featureandcolour,irrespectiveofwhetherthisisonjoistsorothersub-floor.Assuchitmaybenecessarytolayfrommorethanonepackatatimesothatthecolourrangeandgradefeaturescanbeblendedthroughthefloor.

3.5 Installation of Strip Flooring Direct to Joists

Construction method

Wherethetimberflooristobesandedandpolished(i.e.featurefloor)fittedfloorconstructionneedstobeused.Withthismethod,thetimberflooringisinstalledaftertheroofcladdingandexternalwallcladdingareinplaceandthehouseisweathertight.Thispreventsinitialdegradingduetowaterandsunlightexposure,andreducesdamagefromtradesduringconstruction.

Sub-floor framing – bearer size, floor joist size and flooring spans

ThesizeoftimbermembersusedtosupporttheflooringboardscanbedeterminedfromAS1684–Residentialtimber-framedconstruction.Forend-matchedflooringprofiles,joistswithaminimumthicknessof35mmmaybeused.Whereplainendflooringisbuttjoinedatfloorjoists,45mmor50mmthickjoistsarerecommendedtoreducesplittingproblemsatbuttends.

Ifinstallingasecretlynailedflooroverjoists,thejoistsneedtobeseasonedtimberorCypressassecretnailingcannotbere-punched.Ifthejoistsshrinkawayfromthefloor,movementofboardsonthefixingsislikelytocauseexcessivesqueaking.

Top(face)nailedfloorsmaybefixedintoeitherseasonedorunseasonedjoists.Iffixedintounseasonedjoists,thejoistsneedtobeofaspeciesnotexhibitinghighratesofshrinkageandbeinsingleorsimilarspecies.Speciesexhibitinghightangentialshrinkageratesorwhicharepronetocollapseordistortionshouldnotbeusedunlessseasoned.Thepotentialeffectsoffloorframeshrinkagerequireassessmentpriortospecifyingororderingunseasonedfloorframing,anddueallowancemadeinthebuildingdesignanddetailing.Similarly,afterinstallation,theeffectsofbothshrinkageandpossiblenailpoppingneedconsideration.

Thetopplaneofthejoistsmustbesufficientlyflattoacceptthetimberfloorandtoprovideafinishedfloorappearancethatalsoappearsflat.

Theallowablespanoftimberflooringisdependentonthetimberspecies,density,grade,thicknessandwhetherornottheflooringisendmatched.Thefollowingtablegivestheacceptablejoistspacingandmaximumspansforvariousflooringproductswhenfixedtotimberjoists.Maximumboardspan(thedistancebetweenwherethetimberissupported)needstobeconsideredininstallationswhereflooringisatanangletothejoists,asthisincreasestheboardspans.

Adequate sub-floor ventilation and a dry sub-floor space are a must for timber floor performance.


Allowable Joist Spacing and Maximum Span of Floorboards.

Installation direct to joists

Inmostinstances,whenlayingoverjoists,boardsaretobesupportedonatleastthreejoists,however,therewillbeinstanceswheresomeboardsmaynotbe(i.e.flooredgesortheoccasionalshorterboardwithinthefloor),butthisshouldbekepttoaminimum.Flooringshouldbelaidinstraightandparallellines.Buttjoinedboardsmustbecuttojoinoverfloorjoistsandjointsinadjacentboardsshouldbestaggered.End-matchedjointsinadjacentboardsshouldnotoccurwithinthesamespanbetweenjoists.Itisessentialthatboardsareincontactwiththejoistsatthetimeofnailing,particularlywhenmachinenailingisused,asthistypeofnailingcannotbereliedontopulltheboarddowntothejoist.

Itisgenerallyrecommendedthatnotmorethan800mmofflooringiscrampedatanyonetime,however,thismaybevariedbytheinstallerdependingontheflooringusedandconditionsinwhichthefloorislaid.Thepressureusedtocramptheboardstogetherwilldifferfromonefloortoanother,dependingonthemoisturecontentoftheflooringatinstallation,theairhumidityandtheaveragemoisturecontentconditionsforthelocation.Asageneralrule,crampingshouldbesufficienttojustbringtheedgesofadjoiningboardstogetherwhilemaintainingastraightline.

Top (face) nail and secret fixing direct to joists

Boardsfortop(face)nailingandcoverwidthsof65mmorlessshouldbetop(face)nailedwithoneortwonailsateachjoist.Boardsfortop(face)nailingandacoverwidthover65mmandupto135mmwideshouldbetop(face)nailedwithtwonailsateachjoist.Boardswiderthan135mmareoftentop(face)nailedwithtwoorthreenails.

Cramping should be sufficient to just bring the edges of adjoining boards together.

Buckling of 80 mm wide Spotted Gum boards secretly fixed to pine joists in a humid locality.


Top(face)nailingistobeundertakenuniformlywithrespecttoedgedistancesandalignmentacrossthefloor.Somevariationduetojoistlayoutmayoccur.Boardsupto85mmwidecanbesecretlyfixedwithastapleorcleatateachjoistandrequireagoodcoverageofflooringadhesivetothejoist.Inhumidandmoistlocalities,additionalcareisrequiredtocaterforpossiblegreaterexpansion.Considerationshouldbegiventoboardmoisturecontents,providingforexpansion,thespecies,joistmaterialandfixingmethod.Insomelocations,top(face)nailingwillbethepreferredoption.Fixingsizescommonlyusedfor19mmto21mmthickboardsareprovidedinthefollowingtable.

Notes: 1. Fixings may vary to some degree between locations due to installers’ experience of local conditions. 2. A continuous bead (6 mm to 10 mm approx.) of flooring adhesive to be applied to the joist.

Recommendedminimumedgedistancefornailingatbuttjointsorboardendsis12mm.Allnails,includingmachinenails,shouldbepunchedatleast3mmbelowthetopsurface.Duringfixing,thejointbetweenfloorboardsandthetopsurfaceoffloorjoistsshouldbecheckedtoensurethatgapsarenotpresent.Ifgapsarepresent,nailsshouldbepunchedtodrawboardstightlyontothejoists.

3.6 Installation of Strip Flooring over Existing Timber and Sheet Floors on Joists

Assessing the existing floor

TimberT&GflooringmaybelaidoveranexistingT&Gfloororsheetfloor(plywoodorparticleboard).Wheretheexistingfloorisstructurallysound,eitheroverlayflooring(generally11mmto14mmthick)orstructuralflooring(generally19to21mmthick)canbelaid.Floorsmaybefixedthroughthesub-floorintothejoistsorintotheexistingflooronly.Wherethereisdoubtoverthestructuraladequacyoftheexistingfloor:

• removetheexistingfloorandusestructuralflooringlaidat90°tothejoists,andfixintothejoists;

• replacethedefectiveboardsorsheetstomaketheexistingfloorstructurallysound(structuraloroverlayflooringmaythenbeused);or

• iftheexistingfloorisnotmadestructurallysound,usestructuralflooringat90°tothejoistsandfixthroughtheexistingfloorandintothejoists.

It should be checked that boards are tight on the joists.

Secret fixing is recommended for boards up to 85 mm in cover width.


Thenewboardsmaybefixedatanangle(otherthan90°)tothejoistsinthefirsttwooptionsabove,providedthatthethicknessofthenewboardsisappropriatetotheincreasedspanbetweenthejoists(asaconsequenceoftheangle).

Top(face)nailsinexistingflooringshouldbere-punchedwherenecessary.Theexistingfloormayneedroughsandingtoprovideanappropriatesurfaceoverwhichthenewflooristobefixed.Adhesivesrequireaclean,structurally-soundfloorthatisfreefromsurfacemoisture,looseparticlesandcontaminants.Insomeinstancessheetsub-floors(substrates)cansagbetweenjoistsandifnotlevelledthesaggingwillshowthroughtothenewfloor.

Itisnecessarytocheckthattheexistingfloormoisturecontentisappropriatetoacceptthenewfloor.Thecauseofanyexcessmoisture(wettingduringconstruction,leaks,inadequatesub-floorventilation,etc)needstobeaddressedpriortoinstallationofthenewfloor.Moisturemetersareunpredictableinsheetflooringandthismaynecessitateovendrytesting.Priortolaying,thenewfloorshouldbeofsimilarmoisturecontent(withinafewpercent)totheexistingfloor.

SqueakingpresentinanexistingT&Gfloormaybereducedbyprovidingabeadofflooringadhesivetofillanygapsbetweentheundersideofflooringandtopsofjoists(causedbycupping,shrinkage,etc).Furtherreductionsmaybeachievedbyfixingaseasonedbatten(approximatedimensions35x45mmor19x60mm),totheundersideofflooring(mid-spanbetweenjoists)andparalleltothejoistsfixedwithafull-lengthbeadofflooringadhesiveandscrewedatapproximately450to600mmcentrestoholdthebatteninplaceuntiltheadhesiveisset.

Installation

Themethodsbelowaregenerallysuitableforboardwidthsupto135mm,bothoverlayandstructuralflooring.

Thesecretfixingofboardsrequiresonestapleorcleatattheappropriatespacing.For(top)facenailingofboardsthroughthesub-floorandintothejoists,twonailsperboardarerequiredateachfixingforboardsexceeding65mmcoverwidth.

Inhumidandmoistlocalities,additionalcareisrequiredtocaterforpossiblegreaterexpansion.Considerationshouldbegiventoboardmoisturecontents,providingforexpansion,boardsize,thespeciesandfixingmethod.Insomelocationstop(face)nailingmaybethepreferredoptionorafullbedofadhesiveused.Overlayflooringcanbemorereactivetochangesinenvironmentalconditionsinducednotonlybyconditionsbeneaththefloorbutalsobysunexposurethroughlargewindowsabovethefloor.Somemanufacturersdonotrecommendthattheir130x19mmorwiderboardsbesecretlyfixedandothermanufacturershavespecificfixingrecommendationsprovidingforthesecretfixingofwiderflooringthatshouldbestrictlyadheredto.

Installationofflooringshouldnotproceeduntilotherconstructionactivities(particularlywettrades)arecompleteanduntilafterthebuildingisroofedandenclosed,withthetemperatureandhumidityascloseaspossibletotheexpectedin-serviceconditions.Asdetailedabove,expansiongapsof10mmminimumshouldbeprovidedatallwallsandotherfixedobstructions,whichareparalleltotherunoffloorboards.Intermediateexpansionjointsshouldalsobeprovidedinlargerfloors(widthatrightanglestoboardsexceeding6metres),togiveanequivalentgapof10mmevery6metres(approx.1.5mmevery800mm)oralternativelytheboardsshouldbelooselycramped.

Secret fixing into sub-floor (substrate) only

Whenrelyingonthesub-floororsubstrateforfixing,boardsshouldbesecretlyfixedwiththefirstandlastfewboardsthatdonotallowsecretfixing,top(face)nailed.WhenlayingoveranexistingT&Gsub-floorthenewflooringmaybelaideitherparallelwiththeexistingboardsorat90°tooratanyotherangletotheexistingboards,providingthesub-floor(substrate)iswithintherequiredflatnesstolerances.Thefixingofthefloormaybeundertakenrelyingonacombinationofmechanicalandadhesivefixing.

Whenfixingboardswithamaximumwidthof85mmatclosecentresupto225mm,beadsofadhesivetoprovideacushionbetweenthetwofloorsshouldbeusedtominimisepossiblesqueaks.Thisisachievedbyusingacontinuousbeadofadhesiveat90°toboardlength,midwaybetweenfixingpoints.Whereflooringadhesiveisusedtoprovidemoreofthefixing,staplesorcleatsmaybespacedupto450mmapartwithbeadsofadhesiveatthefixingpointsandmidwaybetween.

Withwiderflooringupto135mm,afullbedofadhesivewithfixingsupto300mmapartisapplicable.Duetotherelianceontheadhesivetoprovidemuchofthefixinginthisinstance,itisimportantthattheadhesivemanufacturer’srecommendationsforusingtheadhesivearefollowed.Surfacecleanliness,flatnessprovisionsandspreadrateareallimportant.FurtherinformationonadhesivesisprovidedinSection4.


For19mmthickflooringstaplesforboardsupto85mmwideshouldbeaminimumof32x15gaugeandcleatsshouldbeaminimumof32x18gauge.Forwiderboardsto135mmx19mm,38mmx15gaugestaplesor38mmx16gaugecleatsarerecommended.Foroverlayflooringwhichisgenerallyupto15mmthick,25mmlongfixingsarecommonlyusedforallwidths.Fixingisalsorequiredwithin50mmofboardends,howeveriftooclosesplittingatendsmayoccur.

Recommended Fixing of T&G Flooring to Sub-floors of Plywood, Particleboard and T&G on Joists(1)

Notes: 1. Fixings may vary to some degree between locations due to installers’ experience of local conditions. 2. Adhesive beads of 6 mm to 10 mm are often applied in a zigzag pattern. 3. Full bed adhesive to be applied to the adhesive manufacturer’s instructions. 4. For overlay flooring up to 15 mm thick a fixing length of 25 mm is commonly used.

Top (face) nailing into joists through the sub-floor (substrate)Whenstructural19mmflooringisused,thefloorshouldbetop(face)nailedwith65x2.5mmmachinenailsor65x2.8mmhand-drivennailsthroughtheexistingfloorandintothejoists.Forthinneroverlayflooring,50x2.5mmmachinenailsor50x2.8mmhand-drivennailsshouldbeused.Inallcases,continuousbeads(6–10mmapprox.)offlooringadhesiveshouldbeprovidedatthejoistsandmidwaybetweenthemtoprovideacushioningeffectbetweenthetwofloors.Boardendsadjacenttowallsshouldbefixedwithflooringadhesiveandnailedtothesub-floor.

3.7 Installation of Strip Flooring over Plywood and Battens on Concrete Slabs

Themethodsbelowaregenerallysuitableforboardwidthsupto135mmwide.Usestructuralflooringonbattensandeitherstructuraloroverlayflooringonplywood.Thesecretfixingofboardsrequiresonestapleorcleatattheappropriatespacing.Fortop(face)nailingofboardstothebatten,twonailsperboardarerequiredateachfixingforboardsexceeding65mmcoverwidth.Fixboardswiderthan135mmtobattenswithtwoorthreenails.

Inhumidandmoistlocalities,morecareisrequiredtocaterforpossiblegreaterexpansion.Considerationshouldbegiventoboardmoisturecontent,providingforexpansion,boardsize,thespeciesandfixingmethod.Insomelocations,top(face)nailingtothebattensmaybethepreferredoptionorafullbedofadhesiveusedonplywoodsub-floors.Overlayflooringcanbemorereactivetochangesinenvironmentalconditionsinducednotonlybyconditionsbeneaththefloorbutalsobysunexposurethroughlargewindowsabovethefloor.Somemanufacturersdonotrecommendthattheir130x19mmorwiderboardsbesecretlyfixedandothermanufacturershavespecificfixingrecommendationsprovidingforthesecretfixingofwiderflooringthatshouldbestrictlyadheredto.

Assessing the concrete slab

Timberfloorsmaybelaidonbattensorplywoodoveraconcreteslab,orbydirectfix.Directfixtotheslab(asoutlinedinSection4)isamorespecialistfieldandappropriateprofessionalsinthisfieldshouldbeconsultedifconsideringthismethod.ThefollowingcoversinstallationofT&Gflooringonplywoodoverconcreteoronbattensoverconcrete.Priortoinstallation,ensurethattheconcreteissufficientlyleveltoacceptthesystem.Wherethereisadeviationofmorethan3mmbelowtwohighpointsinaslabwithina1.5mlength,aconcretetopping(levellingcompound),grindingorpackingshouldbeused.Slabsongroundshouldbeconstructedwithacontinuousunder-slabvapourbarrier(inaccordancewithAS2780).


TimberfloorsshouldnotbeinstalleduntiltheconcreteslabhasbeenassessedinaccordancewithAppendixA3.Generally,theslabwillneedtohavecuredforatleast4months,however,ifduetomoistureassessmentsorageofaslabitisconsideredtobenearreadytoacceptafloor,appliedmoisturevapourbarrierscanprovidethenecessaryprotectionfromslabmoisture.

Methods to lay timber floors over concrete slabs include battens, direct adhesive fix and over plywood. Direct adhesive fix should be undertaken by professional floor installers.

Installation

Whenfloorsaretobefixedoveraplywoodsub-floor,overlayorstructuralflooringmaybeused.Whenfloorsaretobefixedtobattensat450mmcentres,structuralflooring(19mmorthicker)istobeused.Theplywoodsub-floororbattensneedtobeatamoisturecontentwithinafewpercentoftheflooringtobeinstalledatthetimeofinstallation.

Installationofflooringshouldnotoccuruntilotherconstructionactivities,particularlywettrades,arecomplete.Thebuildingshouldberoofedandenclosedwiththetemperatureandhumidityascloseaspossibletotheexpectedin-serviceconditions.Forsecretfixing,onestapleorcleatperboardateachfixingisrequired.Fortop(face)nailingtobattens,boardsexceeding65mmcoverwidthrequiretwonailsperboardateachfixing.Asdetailedaboveexpansiongapsof10mmminimumshouldbeprovidedatallwallsandotherfixedobstructions,whichareparalleltotherunoffloorboards.Intermediateexpansionjointsshouldalsobeprovidedinlargerfloors(widthatrightanglestoboardsexceeding6metres),togiveanequivalentgapof10mmevery6metres(approx.1.5mmevery800mm)ortheuseofloosecramping.

Asanaddedprotectionagainstmoisturefromtheslab(fromslabedgeeffects,beamthickening,etc)orminorbuildingleaksa0.2mmthickpolyethylenemembraneisrecommended.Thepolyethyleneshouldbelappedby200mm,tapedatthejointsandbroughtupthewalls(orfixedcolumns,etc)toorabovetheintendedtopsurfaceoftheflooring.Thepolyethyleneisthencoveredbytheskirting.Notethatfixingsofplywoodsub-floorsorbattensthroughthepolyethylenearenotconsideredtoreducetheoveralleffectivenessofthemembrane.Anappliedmoisturevapourbarrierovertheslabmayalsobeusedtoprotectagainstpossibleslabmoisture(seeAppendixC–SlabMoistureAssessment).

Fixing recommendations – plywood sub-floors to concrete slabs and flooring to plywood

Plywoodsub-floorsshouldbestructuralgrade,aminimum15mmthickandwithatypeAbond.Plywood12mmthickinalsousedbyfloorinstallersbutwiththisthicknessgreaterconsiderationneedstobegiventoslabevennessandthepossibleperforationofmoisturebarriersbeneaththeplywood.Sheetsmaybeinstalledina‘brick’patternorat45°tothedirectionofthestripflooringwithaminimum6mmgapbetweensheetsandaminimum10mmgaptointernalandexternalwalls.

Secret fixing to a plywood sub-floor. A polyethylene moisture barrier has been placed over the slab and both the plywood and flooring are clear of the wall.


Inmostcasestheplywoodisfixedtotheconcrete.Wherefortechnicaloracousticreasons,theplywoodcannotbefixedtotheconcrete,theplywoodsheetsarelaidat45°tothedirectionofthefloorboardsandtheendjointsoftheplywoodsheetsarestaggered.Variousmethodsoffixingtheplywoodsheetstotheconcreteareused,includingadhesivesandmechanicalfixing.

Theoptiondetailedbelowisforhand-drivenspikes,whichprovidessolidfixingtotheslab:

• Slabsshouldbeflat.Thereshouldnotbemorethan3mmbelowastraightedgespanningbetweentwohighpointsin1.5m.Ifnot,theeffectneedstobeassessedandatoppingcompoundprescribedforthepurposeorothermeasurestoprovideasatisfactoryfloorinstallationshouldbeused.

• Install0.2mmpolyethylenevapourbarrier.

• Fixplywoodsheetsthroughthemembranetotheslabwithhand-driven50mmlongby6.5mmspikes(‘PowersSPIKE’orequivalent).Aminimumof20spikestobeusedper2400mmx1200mmsheet,equallyspaced(4rowsof5spikesdownthelengthofthesheet)andwiththeouterspikes75mmto100mmfromthesheetedge.Ifabrickpatternisused,itispreferablethatsheetsbestaggeredby900mmsothatfixingsdonotlineupfromsheettosheet.

Thefixingofthefloormaybeundertakenrelyingonacombinationofmechanicalandadhesivefixing.

Whenfixingboardswithamaximumwidthof85mmatclosecentresupto225mm,beadsofadhesivetoprovideacushionbetweenthetwofloorsshouldbeusedtominimisepossiblesqueaks.Thisisachievedbyusingacontinuousbeadofadhesiveat90°toboardlength,midwaybetweenfixingpoints.Whereflooringadhesiveisusedtoprovidemoreofthefixing,staplesorcleatsmaybespacedupto450mmapartwithbeadsofadhesiveatthefixingpointsandmidwaybetween.

Withwiderflooringupto135mm,afullbedofadhesivewithfixingsupto300mmapartisapplicable.Duetotherelianceontheadhesivetoprovidemuchofthefixinginthisinstance,itisimportantthattheadhesivemanufacturer’srecommendationsforusingtheadhesivearefollowed.Surfacecleanliness,flatnessprovisionsandspreadrateareallimportant.FurtherinformationonadhesivesisprovidedinSection4.

For19mmthickflooringstaplesforboardsupto85mmwideshouldbeaminimumof32x15gaugeandcleatsshouldbeaminimumof32x18gauge.Forwiderboardsto135mmx19mm,38mmx15gaugestaplesor38mmx16gaugecleatsarerecommended.Foroverlayflooringwhichisgenerallyupto15mmthick,25mmlongfixingsarecommonlyusedforallwidths.Fixingisalsorequiredwithin50mmofboardends,howeveriftooclosesplittingatendsmayoccur.

Plywood mechanically fixed to concrete. Adhesive spread prior to fixing.


Notes: 1. Fixings may vary to some degree between locations due to installers’ experience of local conditions.2. Adhesive beads of 6 mm to 10 mm are often applied in a zigzag pattern.3. Full bed adhesive to be applied to the adhesive manufacturer’s instructions.4. For overlay fl ooring up to 15 mm thick the fi xing length of 25 mm is commonly used.

Fixing recommendations – battens to concrete slabs and fl ooring to battens

Battensaretobeseasonedandmaybeeitherhardwoodorsoftwood.Battensmaybefixedtotheslabusing75x6.5mmgunnailsat600mmmaximumspacing.‘PowersSpikeFasteners’withaminimumembedmentof32mmorequivalentfastenerat900maximumspacingorM6masonryanchorsat900mmmaximumspacing.Battenspacingisdependentonthespeciesandgradeoftimberflooringusedandthespacingshallbeuptothatforflooringbeingsupportedbyjoistsprovidedaboveinthesectiononthe‘InstallationofStripFlooringOverJoists’.Wherehigherexpansionforcesareexpectedafterinstallation(e.g.warmhumid,ruralandcoastalenvironments)battenspacingisoftenreducedtoprovidemorerobustfixingandfloorsecretlyfixed.Ifbattensareaminimumof35mminthickness,thespacingbetweenfasteningsmaybeincreaseduptoamaximumof1200mmprovidedminimalfloorexpansionforceisexpectedafterinstallation.Againwherehigherexpansionforcesareexpectedafterinstallationamaximumfixingspacingof600mmismorefrequentlyusedwithfixingineachadjacentrowoffsetby300mm.Thisistoreducetheriskofthebattensliftingofftheslabsurfaceunderfloorexpansionresultinginsmallsurfaceundulationsinthefloorandmorefrequentdrummysounds.


Boardsforsecretfixingupto135mmwidecanbesecretlyfixedwithonestapleorcleatateachbatten.Adhesiveisrecommendedforboardwidthsgreaterthan85mmandoftenusedwithboardsupto85mmwide.Boardsfortop(face)nailingandcoverwidthsof65mmorlessshouldbetop(face)nailedwithoneortwonailsateachbatten.Boardsfortop(face)nailingandacoverwidthof80mmandupto135mmwideshouldbetop(face)nailedwithtwonailsateachbatten.Boardswiderthan135mmaregenerallytop(face)nailedwithtwoorthreenailsintothickerbattens.Top(face)nailingistobeundertakenuniformlywithrespecttoedgedistancesandalignmentacrossthefloor.Somevariationduetobattenlayoutmayoccur.

Inwarmerhumidormoistlocalities,additionalcareisrequiredtocaterforpossiblegreaterexpansion.Particularconsiderationshouldbegiventoboardmoisturecontents,providingforexpansion,boardsize,thespeciesandfixingmethod.Thefollowingtableandfigureoutlinetheminimumbattensizeandrecommendedfixingrecommendationsforstructural19-21mmthickflooringtobattens.Thenotestothetableoutlinethatsomefixingoptionsaremoresuitableforsomelocationsandinstallationenvironmentsthanothers.

Notes: 1. Fixings may vary to some degree between locations due to installers’ experience of local conditions.2. High density refers to species with published densities above 750 kg/m3.

3. Cleats of an equivalent length (50 x 16 g, 45 x16 g, 38 x16 g) may be used in place of the staples.4. In localities where the internal environment is heated during colder winters (e.g. Sydney and Melbourne) the smaller fi xing size is more commonly used. In seaside locations, moist rural locations or where humid weather frequently enters the dwelling (Queensland) larger fi xings, adhesive and battens at reduced centres are often used.5. A continuous bead (6 mm to 10 mm approx.) of adhesive to be applied to the batten.6. The practice of top nailing into 19 mm battens constitutes a recommended practice in Sydney and surrounding areas. In warmer, more humid locations more robust fi xing is needed due to greater fl oor expansion forces.

Recommended fi xing of T&G Flooring to Battens over a Slab


Installation by Direct Adhesive Fix to Slabs This section outlines the recommended practices for laying timber strip floors by direct adhesive fix to concrete slabs. This is one of three methods of laying a timber floor over a concrete slab and practices within this category differ between states. Timber floors are also regularly laid on plywood or battens over a concrete slab and procedures for these two methods are covered in Section 3.

Whenlayingafloorbythismethod,whichmayincludeadditionalpinning(eithertemporaryorpermanent)thereareissuestoconsiderinadditiontothosewhenlayingoverplywoodorbattens.Greaterknowledgeandunderstandingofconcreteproperties,levellingcompounds,moisturevapourbarriersandadhesiveperformanceareallnecessary.Installationshouldnotbeattemptedwithoutthisknowledgeandsoundexperienceofgeneraltimberfloorinstallationpractices.

Oneoftheadvantagesofdirectadhesivefixisthatitcanovercomepossibleheightrestrictionsandthemethodisnecessarywithpre-finishedflooring.However,itisnotuncommonforsuchfloorstohavesome‘drummy’areasandthisneedstobeacceptedtosomedegree.

WesternAustralia,withitssandysoilsandpredominanceofslab-on-grounddoublebrickhouseconstruction,hasdevelopedaparticularmethodofinstallationandthevastmajorityofalltimberfloorsinthatstatearelaidbythatmethod.Inotherstates,methodsdifferandthereisamuchgreatermixoffloorsbeinglaidbydirectstick,overbattensandoverplywood.Itisnotuncommonforsomeindividualinstallersintheeasternstatestolayfloorsoverslabsbyeachofthesethreemethodsdependingonclientpreferencesandsiteconditions.Floorswillhaveadifferentfeelandsoundwhenwalkedondependingonwhattheyarelaidover.InWesternAustraliaATFA-WAhasaspecific‘BestPractice’guidewhichprovidesinformationonpracticesandflooracceptabilityinthatstateandsomeprovisionsinitmaydifferfromthoseprovidedbelow.

4.1 Assessing and Preparing the Slab

Slabassessmentrequirementsaredefinedbymostmoisturevapourbarrierandadhesivemanufacturers.Thesedifferbetweenproductmanufacturersbothincontentandspecificdetails.Practicesusedinslabassessmentshouldmeettherequirementsoftherespectiveproductmanufacturerandtheassessmentmayneedtogobeyondwhattheyrequire.

Aspectsthatcommonlyneedtobeassessedandwhatisrequiredtoprepareaslabareoutlinedbelow:

• Slab Moisture –DetailsregardingthemoistureassessmentofslabsisprovidedinAppendixCandthisneedstobereferredto.Itisimperativethatslabsaresufficientlydrytoacceptatimberfloortoavoidcupping,inadequateadhesionandexpansionrelatedissuesthatmayarisefromtheredistributionofmoistureinaslabafterthefloorislaid.Moisturevapourbarriersareoftenusedasanaddedprecaution.

4Spotted Gum direct stick overlay floor.


• Surface Contaminants – Itisexpectedthatthesurfacewillbeclean,dryandfreeofpaint,oil,grease,concretecuringsealers,previousadhesivesandloosematerial,etc.Therehavebeenanumberofinstanceswhereincompatibleslabcuringcoatingsthatarenotvisibleatthetimeoffloorinstallationhavepreventedadhesion.Waterdropletsonaslabshouldfreelysoakintothesurface;ifnot,thepresenceofasealerorsimilarshouldbesuspected.Mechanicalremovalisconsideredthemosteffectivemeansofcontaminantremoval(grindingandshotblasting,etc).

• Slab Construction and Soundness –ItisgenerallyacceptedthatthenewslabswillhavebeenconstructedtomeetAS2870forresidentialslabsandfootingswithasteel-trowelledfinishandwillbefreeoffloatingridges.Adhesive-fixedtimberfloorscanfailiftheslabisnotsuitablystrongandthepossibilityofweaksurfacelayersorpatchesoflowerstrengthneedstobedetermined.Wheresuspected,thesurfaceshouldbetestedforweaknessandhollowsounds.Anyweakmaterialneedstoberemovedandrepaired.

• Flatness and levelling – Flatnessprovisionsdifferbetweenadhesivemanufacturerswithmanyindicatingarequiredflatnessof3mmin3m.Themethodofmeasurementisnotgenerallyoutlinedbutitwouldbereasonablethatanydeviationisnotmorethan3mmbelowtwohighpointswithina3mlength.Self-levellingcompoundswithhightensilestrengthandrapiddryingtimesmayberequiredtoleveltheslaboralternativelyhighspotsmaybegroundoff.Ifamoisturevapourbarrieristobeapplieditisusuallyappliedbeneaththelevellingcompoundandprimedpriortothelevellingcompoundbeingapplied.Theprimerenhancesbondstrengthbutmaynotbecompatiblewiththeadhesive.Insuchinstances,careisneededtoensurethatallprimeriscovered.

• Insomesituations,particularlywhenthereissomeuncertaintyoverslabintegrity,ithasbeenbeneficialtoundertakebondtesting.Thisiswherehalfthelengthof300mmlongpiecesofflooringaregluedtotheslabandafter24hourslevereduptoensuresufficientstrengthandappropriatefailure.Theflooringshouldnotbeeasytoliftandfailurethroughtheadhesiveandthetimberwouldbeexpectedwithminimalfailurefromtheslab.

4.2 Moisture Vapour Barriers

Manyoftheadhesivecompaniesmanufactureacompatiblemoisturevapourbarrierorwillstatewhatmoisturebarrierisrecommendedwiththeirproduct.Moisturevapourbarriersarenotmandatorybutmayberequiredbyadhesivemanufacturersaspartoftheirwarrantedsystem.Manyinstallersassessslabmoistureandwilldeterminetheneedtoapplyoneornot.Thepurposeofthemoisturevapourbarrieristoreducetoasufficientlylowlevelanyresidualmoisturemigrationfromtheslabsothatthetimberflooringaboveisnotaffected.Amoisturevapourbarrierisnotawaterproofmembrane.Requirementsdifferbetweenproductsandusuallytheapplicationofoneortwocoatsisrequiredwithapplicationbybrushorroller.Aswithallcoatingsystems,temperatureandhumidityconstraintsapplyaswellasrecoatingintervals.Acuringperiodappliespriortotheapplicationofadhesivesorlevellingcompoundandthereisoftenatimewindowforapplicationfortheadhesive,outsideofwhichfurtherpreparationisnecessary.Aspectsrelatingtosurfacepreparationasapplicable,suchassoundnessandsurfacecontaminants,areoutlinedabove.

Intimberflooringapplications,itisoftennecessarytotemporarilyorpermanentlypinthefloortotheslab.Followingclarificationontheeffectofthisfromanumberofmoisturevapourbarriermanufacturersandaftertestingundertakenbythesecompanies,theyconsideredalimitednumberofnailpenetrationsasacceptablewiththeirproducts.


Effect of fi xings through moisture vapour barriers.Whenafixingisputintoaslabandthemoisturevapourbarrierisperforated,youwouldexpectsomeleakageofmoisturevapouraroundthefixing.Ifthefixingwasremoved,therewouldbeevengreatermoisturevapourtransmission.Theindicativediagramaboveshowstheeffectsofmoisturevapourtransmissionthroughmoisturevapourbarriersthathaveperforationsfromfixings.Asindicated,theeffectsaresmall.

Whenafixingisremoved,therewillgenerallybesomedamagetothemoisturevapourbarrier.Considerationmustbegiventothis.Damagecanexposeamuchlargerareathantheholesizeofthefixing.Forthisreason,itisbesttoleavefixingsinplace.Iftemporaryfixingisusedwithclampsorsimilarforcrampingthefloor,thismaymeangrindingthefixingoffflushwiththesub-floorsurface.Itisnecessarythatnailsarevertical.Anglefixing,aswouldoccurwithsecretfixing,invariablychipstheconcretesurfaceandmoisturevapourbarrier.

Companiesthathaveundertakentestingconsiderthatupto10fixingspersquaremetreofadiameterof3to4mmwouldnotsignificantlyaffecttheperformanceofthemoisturevapourbarrierorthetimberflooringabove.Providedthemanufacturers’recommendationsarecompliedwithinallrespects,thisnumberofpenetrationsshouldnotaffectthemanufacturer’swarranties.Toensurethatwarrantiesaremaintained,confirmationshouldbesoughtfromthespecificmoisturevapourbarriersupplierthatthisappliestotheproductbeingused.

Slabsthataredrierpresentlessriskfrommoisturevapourtransmissionanditisrecommendedthatallslabsbeatorneartherecommendedlevelsfortimberfloorsoverconcreteslabs,priortotheuseofmoisturevapourbarriers(refertoslabmoistureassessmentinAppendixC).

4.3 Adhesives

Mostoftheadhesivesonthemarketfordirectstickflooringareonepartmoisturecuringpolyurethaneproducts.Recommendationsfortheuseoftheseproductsdifferbetweenmanufacturers,bothincontentandspecificdetails.Itshouldnotbeassumedthateachproductisthesameinitsproperties.Somedifferencessuchascuredflexibilityandfoamingcharacteristicsareeasilyobserved,however,othercharacteristicssuchasinitialhold,curingrateandfinalstrengtharenoteasytodiscern.

Direct stick 80x19 mm Standard Grade Blackbutt.


Allmajormanufacturershavedatasheetsfortheuseoftheirproductsandtheseneedtobeadheredto,specificallynotingthattherequirementsinparticularaspectsofusemaydifferbetweenproducts.

Aspectstobeawareoforemphasisedinclude:

• Adhesivesarenotdesignedtobemoisturebarriersandwillnotperformthistask.

• Theadhesivemaynotbecompatiblewithprimersusedwithlevellingcompounds.

• Thecuringrateformoisturecuringadhesiveswillbeslowerinverydryconditionsandcandiffermarkedlybetweenproducts.

• Theworkingtimewilldifferbetweenproductsandneedstobeadheredto.

• Fullcuringcanrangeuptoabout7days.

• Cleanupiseasierwithsomeproductsthanothers.

• Trowelsizeandangleatwhichthetrowelisheldarebothimportantinordertoobtainthecorrectspreadrate.

• Itisnecessarythatsomemeansofholdingboardsisinplace(weightingorpinning)whiletheadhesivecuresisundertaken.

• Floorsandingisoftennotrecommendedtobeundertakenforabout3days.

Adhesivesprovidesignificantrestrainttoboardmovement(shrinkageandswelling),however,manyofAustralia’shardwoodsareverydenseandtheswellingforcesgeneratedcanexceedthatoftheadhesives.Irrespectiveofhowflexibleanadhesiveis,asimilaramountofmovementoftenoccurswithhigherdensityspecies.Inlocationswhereatmosphericmoistureuptakecausessignificantexpansionpressure,‘peaking’canalsooccur.Thisisapressure-inducedcuppedappearanceacrossafloor.Someflooringprofilesaremorepronetothisthanothers.Profileswithhigherlevelsofundercutorrelief(differencebetweenupperandlowercoverwidths)aregenerallymorepronetopeaking.Toreducein-serviceexpansionpressure,itisalsonecessarythattheaveragemoisturecontentoftheflooringatthetimeofinstallationisalignedascloselyaspossibletothatwhichtheinstalledfloorwillattainin-serviceduringhumidperiods.

4.4 Direct Stick Installation Practices

Practices in the eastern states of Australia

Installersmayuseavarietyofpracticestolayfloorsbythismethodandthefollowingoutlinesthemorecommon.

Generalcleanlinessisimportantandthefloorareamustbekeptcleanandfreefromdebrissuchasstonesthatcouldpreventadequatecontactbetweentheboardandtheslab.Similarly,itmustbeensuredthatpartially-curedadhesiveonthetroweldoesnotlessentherequiredspreadrateorheightoftheadhesive.Adhesiveheightisparticularlyimportanttoensurebondingwithvariationsinslabflatness.Theadhesivetobeusedmaybeineithersausageformorpail.Ifinapail,anyskinformedshouldbecarefullyremovedtothepointwheretheadhesiveissoftbelow.Theadhesivecanthenbesqueezedfromthesausageordistributedfromthepailontotheslabsurface.Withpails,thelidshouldbelooselyplacedonapailbetweenapplicationstoreducetheriskofcuringinthepail.Careisalsonecessarytokeepedgesoflidandpailcleanifovernightstorageofapart-usedpailisnecessary.Insuchinstancesthepailwithlidfirmlyattachedisplacedupsidedown.

Generally,forvisualandexpansionreasons,boardsarelaidparalleltothelongestwallintheroomorwhereboardswillrunlengthwisedownhallways.

Fromthewallwherethefloorisbeingstarted,achalklineparalleltothewallis‘flicked’onthefloorapproximately800mmoutfromthewall.Thedistanceneedstotakeintoconsiderationtheactualboardwidthandanallowanceofatleast10mmforexpansionbeneaththeskirting.

Temporarilyfixthe‘startingboard’withadhesiveandconcretenails,oftencalled‘mickeypins’,tothislinewiththetonguefacingthe‘startingwall’.Ensurethatthe‘starterboard’remainsinfirmcontactwiththeadhesiveuntiltheadhesivehascured.Thetemporarypinsmayberemovedaftertheadhesivehassufficientlycuredwhichisgenerallyatleast24hours.

Atbothendsofthefloor,therequiredminimum10mmexpansionallowanceisalsotobeprovided.Apieceoftimberoftherequiredexpansionwidth,placedalongthewallandlaterremoved,canbeusedtoassistinprovidinganevengap.


Onlyusesufficientadhesivefortheareathatcanbecoveredinabout20minutes.Thismaybeonly3to4boardsatatime.Adhesivemanufacturersrecommendthattheadhesiveshouldgenerallybespreadatrightanglestotheedgeoftheboard.Therecommendednotchedtrowelshouldbeused,takingcaretoensuretheappropriatespreadrateandheightofadhesiveismaintained.

Workingfromtheareabetweenthe‘starterwall’and‘starterboard’(nowfixedinplace),begininstallingthefloorlefttorightfromtheendwall,maintainingtherequiredexpansiongap.Laythefirstrowofboardsawayfromthe‘starterwall’byslottingthetongueofeachboardintothegrooveofa‘starterboard’andthenpresstheboardfirmlydownintotheadhesive.

Whenlayingtheboardsitisnecessarytopositionthetongueandgroovetogetherandpresstheboardintotheadhesiveassignificantslidingactionwillspreadtheadhesivemorethinly,loweringitsheight.This,inturn,canresultinpoorbondingbetweentheboardandslab.

Inthefirstroweachboardislaiduntilthewallisreachedwherethefinalboardwillneedtobecuttofit,ensuringtherequiredexpansiongapisalsoprovidedatthiswall.Aboardshouldbechosensothattheoff-cutislongenoughtobeusedatthestartofthenextrow.Witheachnewrowtheboardsshouldbegentlytappedtogether,usinganappropriateblocksoasnottodamageboardedgesandtoensureatightfit.

Continuetolaythefloorlefttoright.Foranydirectadhesive-fixedfloortoperform,theboardsmustbehelddownwiththeadhesivecontactingbothboardandslabwhiletheadhesivecures.Systemsgenerallyusethetemporaryconcretenails(asabove)orweights(filledbags,filledpailsorrailwayironsetc).Duringtheinstallation,temporarypinningwillberequiredevery800mmorsoorthefloorwillneedtobeweightedtoensurearelativelyevenweightdistribution.

Itisgoodpracticetoensurethatendjointsareatleast450mmapartandthatjointsdonotclustertogetheroralign.Thispracticeprovidesafloorthatismorevisuallyappealing.Iftherearemanyshortboardlengthsintheflooring,thismaynotbeeasyorpossibletoachieve.

Whenthewalloppositethe‘startingwall’isreachedthefinalboardshouldbescribedandcut,againensuringthattherequiredexpansionallowanceisprovidedalongthefulllengthofthewall.Notethatthewallsintheroommaynotbeparallel.

Oncethemainfloorareahasbeenlaid,theareanearthestartingwallcanbecompleted.Atanappropriatetime,alltemporaryfixingsorspacerscanberemoved.

Anumberofadhesivemanufacturersindicatethatfloorsshouldnotbesandedforatleastthreedays.Withsomeflooringproductslongerperiodscanbebeneficial.

Practices in Western Australia

InWesternAustralia,concretenailsapproximately3mmindiameterprovidemechanicalfixingthroughthetopsurfaceoftheboardsinadditiontoafullbedofadhesivebeneaththefloor.Thenailingisdonerandomlythroughoutthefloor,particularlyinareaswheredrummyspotswereobservedduringinstallation.Carefulcolourmatchingofthefillerresultsinthenailpenetrationsblendinginwiththefloor.Thefollowingoutlinesperformance-basedconsiderationsforacceptablepracticebyWestAustralianinstallers.Individualpracticeswillvarytosomedegreebetweeninstallers.

The nail penetration is to the bottom right of the photo.


Sub-floors and underlay

Surfacesmustbecleanandfreefromsubstanceswhichmaycompromisetheadhesivebond.Thesurfaceistobeinasoundconditionandsuitableforthepurpose,thatiscohesiveinstructureandabletowithstandtheforcesresultingfrompossiblefloorexpansionabove.

Cementitiousscreedsorconcretescreedingmayberequiredtopatchorlevelsub-floorswhichareoutsidetheflatnesstolerancesortorectifysurfacesunsuitableforgluefixedinstallations.Asub-floorisgenerallyconsideredsufficientlyflatwhennopartofthesub-floorismorethan5mmbelowa3mlongstraightedgeplacedatanylocationonthesub-floor.Screedapplicationshouldbeinaccordancewithmanufacturers’instructions.Primersorbondingadditivesarerecommendedtoenhancethebondstrengthofthescreed.Itisessentialthatallcontaminationssuchaspaint,plaster,oldadhesiveorPVAsealersberemovedcompletelypriortoscreeding.

Underlaymaybeusedasabaseforglue-fixedtimberflooringandcommonproductsarewoodfibreboard,cementfibreboardandplywood.Underlaysshouldbeglue-fixedandnailedtoachieveasoundbase.Underlaythicknesscanvaryandtheinstalledproductmustbewellbondedandsolid.

Removalofoldfloorcoveringssuchascarpet,vinyls,etc,isoftenrequiredpriortoplacingglue-fixedtimberflooringandtheslabmayneedfurtherworktoprovideasuitablesubstrate.

Ifthereisdoubtaboutthesuitabilityorotherwiseofasub-floorforglue-fixedtimberflooring,atriallaminationshouldbecarriedout.

Moisture testing

Moisturetestingisrequiredpriortotheinstallationofglue-fixedtimberflooring.Themoisturetestingsurveyshouldincludetheproposedtimberflooringandtheslab.Wherepractical,theaveragerelativehumidityassociatedwiththeinstallationsiteshouldbeestablishedwhichwillassistinconfirmingthesuitabilityofmaterialsandsiteconditions.

Whenmoisturevapourbarriersareappliedtotheslab,itisnotconsiderednecessarytoconductmoistureassessmentoftheconcreteslab,providingtheslabisatleast4monthsold.

Slab vapour barriers

Slabmoisturevapourbarriersareusedtoprotecttimberflooringfromcontaminationviaslabmoisturepresentatthetimeofinstallationandasinsuranceagainstmoisturethatmayentertheslabduringthein-servicelifeoftheflooring.Moisturevapourbarriersneedtobecompatiblewiththeproposedadhesivesystemandinstalledinaccordancewiththemanufacturers’recommendations.

Adhesives

Adhesive,generallypolyurethanebased,shouldbeappliedusinganotchedtrowelasrecommendedbythemanufactureroftherelevantproductandthetimberflooringshouldbewelladheredtothesub-floororunderlay/sub-floorsystem,achievingasolidbondwithnounderfootmovementdetectableafteradhesivecuring.Whenaboardisplacedintoabedofadhesiveappliedtorecommendedpractices,thetransferofadhesivetotheundersideoftheboardwithcontactbeingmaintainedbetweenthesurfacesshouldachieveaminimumof75%coverage.Some‘drummy’boardscanbeexpected.

Clamping

Clamping/crampingofglue-fixedT&Gtimberflooringisappliedtoreducethegapsbetweenboards.Thedegreeofclamping/crampingrequiredwillvarywitheachproductandconsiderationshouldbegiventositeconditionsandtheinstaller’sevaluationoftheproduct.Notallinstallationsaregap-freeandsomegapsareconsiderednormalandacceptableinglue-fixedtimberflooring.Thefillingorgapsinsuchfloorsresultinginanongoingcoherentsurfaceisanacceptablepractice.

Supplementary fixing

Supplementaryfixingiscarriedoutprimarilytoholdthetimberboardsortimbersectionsinplacewhiletheadhesivesets.Thesefixingscanbepermanentortemporaryandcanbeappliedmechanicallyormanually.Theamountoffixingscanvarysignificantlyandareoftenrandomlyappliedacrossthefloordependingontheflatnessofthesub-floor.Theamountandtypeoffixingsaredeterminedbytheinstallerandbasedonsiteandmaterialconditions.Allholesorpuncturemarksresultingfromsupplementaryfixingrequirefilling.


Sanding and Finishing Timber FloorsThe sanding and finishing process is particularly important to the overall performance and appearance of the timber floor, and offers a wide array of methodologies and coating systems. The practices outlined are those employed broadly throughout the industry, however variations on sandpaper grades and procedures are common.

Theaiminallcasesistoprovideasmoothsurfacewiththedesiredsurfacecoatingsuitablyappliedtogiveanevenlevelofsheenacrossthebodyofthefloor.Itisimportantthatwhenthefloorisbeingsandedandfinishedthefloorisnotwalkedonbyanyoneunlessunderthesupervisionofthesanderandfinisher.Simplethingssuchasflyspray,siliconesealer,bootsandbarefeetcandetrimentallyaffectthefloorfinish.Generallyfloorsareoutofboundstoeveryoneuntilthefinisherindicatesthattheycanbewalkedon.

5.1 Assessing the Floor Prior to Sanding

Priortosanding,theconditionofthefloorshouldbeassessedtoensurethatitissuitableforsanding.Thismayincludeassessingverticalmovementatboardorend-matchedjoints,anappraisaloftheoverallconditionofthefloor(e.g.degreeofcuppinginboards,gappingatboardedges,signsofmoisture)andiftherearesignsofabnormalmoisturecontent.Itshouldalsoincludetakingandrecordingmoisturecontentsoftheinstalledfloor.Thisensuresacompletehistoryofthefloor,shouldissuesariseinthefuture.Anyissuesshouldbeprovidedinwritingtotheapplicableperson(e.g.principalcontractor,owner)andanappropriatecourseofactiontaken.Itisgoodpracticetoletthefloor‘settle’foraperiod,whichmaybe3to14daysbeforethesandingprocesstakesplace.Thisperiodisalsobeneficialforcuringofadhesiveswhereutilised.

5.2 Preparation for Sanding

Punching nails and filling nail holes

Beforethesandingprocesscanbegin,ensurethatallnailsarepunchedaminimumof3mmbelowthesurfaceoftheboards.Anynailthatisnotsuitablypunchedwillpotentiallydamagethesandingequipmentandaffectthesandingprocess.Itisimportanttonotethatsecretnailedfloorsmayhavebeentop(face)nailedadjacenttoawallorotherareaswhereaccessislimited.

Thepunchednailholescanthenbefilledwitheitheroilornon-oilbasedfiller.Oil-basedfillersmaybleedoilintothetimberandaffectthecolourofthewoodsurroundingthenailholeormaynotbecompatiblewithvariouscoatingproducts.Thecolourofthefillershouldbecarefullyselectedinordertominimiseanyvisualimpactofthefiller.Manyoftheseproductsaresoldincolourspre-matchedtospecificspecies.Inmixedspeciesfloors,orwheresignificantcolourvariationsarepresent,itisusualtomixorselectaneutralcolourthatisslightlydarkerthanmid-rangebetweentheextremesofcolour.Generally,allfillersareslightlydarkerandthisallowsfortheboardstodeepenincolourfollowingfinishingandUVexposure.

Prior to sanding, the floor should be assessed to ensure that it is in a condition suitable for sanding.

Nails to be punched and holes filled.

5


Fillingcanbedoneatthisstageorafterthefirstcoatoffinishisapplied.Byfillingafterthefirstcoatanypotentialforthefillertoimpactonthesurroundingtimberthroughbleedormoistureisminimised.Inallcases,thefillermustcompletelyfilltheholesoasnottoaffectthefinishquality.

Cleaning

Thefloorrequiresthoroughcleaningtomakeitfreefromdirt,gritanddebris.Theseparticlescancausedeep,unevenscratchinginthetimbersurfacerequiringsubstantialadditionalsandingtoremove.Thefloorshouldinitiallybesweptfollowedbyvacuuming,payingparticularattentiontoareaswhicharenoteffectivelycleanedbysweeping,suchasgapsunderneaththeskirting,corners,windowsillsandthelike.Thevacuumshouldhavesufficientcapacityintermsofbothsuctionandfiltrationtosatisfactorilycleanthefloor.

Itisimportanttoremoveanymaterialsthatmaypotentiallyimpactoneitherthesandingorcoatingprocess.Additionalcareshouldbetakenwithsilicone-basedsealantsthatmayhavebeendroppedontothefloor.Theseproductscanpotentiallybewidelyspreadthroughthesandingprocess,affectingthebondbetweenthecoatingandthetimber.

Protection

Duringthesandingandfinishingprocessitisimperativethataccesstotheareaoftheworkberestricted.Anytradesworkinginoraroundtheareacanpotentiallygeneratedust,wetthefloor,introducesilicone-basedmasticsandsealants,walkovertheareaorgenerallycontaminateit.Clearinstructionsshouldalsobegiventotheowneroroccupantsregardingaccess,openingwindowswhichmayblowdustoverthearea,andthetimerequiredforcoatingsystemstoadequatelycure.

5.3 Sanding

Thesandingoperationwillvarybasedontheconditionofthefloorandthehardnessoftheflooringspecies.Wherethefloorisbeingsandedforthefirsttime,thesandingprocessismadeupofanumberofseparatesandingstages,whichgenerallystartwithacoarsepaperandprogresstoarelativelyfinegradeofpaper.Itshouldbenotedthatthesandingprocessiseffectivelyscratchingoffthesurfaceoftheboards,andthereductioningradesofpapermeansthatyoustartwithaseverescratchingactionandfinishwithamoresubtleaction.

Level/basic sanding

Thelevel/basicsand,asthenamesuggests,istocuttheboardslevel,takingoutanyridgesorhighpointsinthefloor.Ittypicallyinvolvesthreepasseswiththesandingmachine.Thelevelorbasicsandingistoprovidealevel,completelysandedfloor–eachofthesandingproceduresthatfollowthissteparedesignedtoremovethesandingscratchesgeneratedbythisinitialstep.

Pass1isdonefromasmallangleupto45°tothedirectionofthegrain(diagonally).Thisangleisdependentuponthelayoutandsizeoftheareatobesanded.Acoarsergradeofpaperisuseddependinguponthespeciesandtheconditionoftheboards.AlowergradeofpapermaybeusedtoenhancetheeffectivenessofthesandingprocessinafloorthatisveryunevenorwithhardspeciessuchasTurpentineorIronbark.

Eachroomissandedstartingatapointthatwillallowthelongestpathoftravelatapproximately45°(orasisdeemedappropriategiventheroomparameters)tothegraindirection(runofboards).Themachineisstartedensuringthatthedrumisnottouchingtheboards.Walkingslowlyforward,thedrumiseasedontotheboards.Aslowwalkingpaceandconsistentpressureismaintained.Attheendofthepass,thedrumisraisedsmoothlyoffthefloor.Thenbywalkingbackwards,pullingthemachine,itiseasedbackontothefloorforthereturnpass.Thepowerleadmustbekeptwellclearofthedrum.

Whentheoriginalstartingpointisreached,thedrumisagaingraduallyraisedoffthefloor.Themachineismovedtotherightorlefthandsideofthefirstpath,ensuringanoverlaptothefirstcutpath.Sandingcontinuesinthatdirection,sandingstripsandmaintainingasimilaroverlapineachforwardandbackwardpass.Whenthelimitofaccessibilityhasbeenreachedinthecorneroftheroom,themachineisbroughtbacktothestartingpointandtheremainderofthefloorissandedinthesamedirectionandmannerbuttotheopposingsideofthefirstcut.Thatis,ifsandedtotheleftofthefirstcut,sandingthentakesplacetotherightofthatfirstcut,ensuringthatthereisanoverlapofaround200mmbetweenthetwosidesofthefloor.

ThesecondpassiscarriedoutontheoppositediagonaltoPass1usingasimilargradepaper.


Thethirdpasscontinuesinthedirectionoftheboardsusingasimilargradepapertoremovethesandinglinesfromtheactionofpasses1and2.Typically,theoperatorshouldstartatapointthatisafewmetresoffthesidewall.Theprocessofwalkingspeedandeasingthedrumontothefloorisaspreviouslydescribed.

Onceaforwardandreversepathissanded,themachineismoved,ensuringanoverlaptothepreviouscutandsandingrecommencesinthesamemanner.Thisprocessiscarriedoutacrosstheroom.Whenthefullwidthoftheroomissanded,theoperatorshouldturn180°andsandtheunsandedbandoffloor.

Atthecompletionofthelevelorbasicsanding,theboardsshouldbegenerallysmoothandfreefromcuppingandmismatchingofsurfacelevelsbetweenadjacentboards.Ifthishasnotbeenachievedthefloorwillrequireadditionalpassestoachievethisstate.

Thesandingdrumshouldnevercontactthefloorunlessmovingforwardorbackward.Doingsowillcutagrooveintothefloor(drummark),whichmaynotberecoverable.Specialistequipmentandmanufacturers’recommendationsanduserinstructionsshouldbefollowed.

Edging

Thesandingmachinewillnotbeabletosandtheboardsalongtheedgesoftheroom,incornersorareasofreducedaccesssuchaswardrobes,etc.Intheseareastheboardsneedtobesandedlevelandgenerallyblendedintothebodyofthefloorusinganedgesander.Themachinemaybeadisc,orbitalorbeltsander.Inallcases,careisnecessarytoensuretheoperationdoesnotdiggroovesintotheboardsandthefinishededgeislevelwiththebodyoftheboards.

During the sanding process progressively finer papers are used.

Second pass of sanding at 45° to board direction.

First pass of sanding at 45° to board direction.

Third pass of sanding in the board direction.


Themostcommonlyusedmachinefortheedgingprocessisthediscsander.Whenusingthismachine,theoperatorshouldmovethemachineinasmooth,evenpatternatboardendsandacrossthegrain.Thepatternofsandingshouldoverlapandblendintothebodyofthesandedfloor.Itisimportantthatthemachineisheldlevelastheboardsareeasilygroovedwithanyunevenpressure.Oneachmovement,themachineshouldsandanapproximately50mmsectionofunsandedfloor.Alongwallsparallelwiththeboards,theedgesandingmachineshouldbesmoothlymoved,backandforth,inthedirectionofthegrainoverlappingsome100mmintothebodyofthesandedfloor.

Onnewandoldfloors,ingoodcleancondition,finergritpapersareusuallysufficientforedging.

Itmaybenecessaryinareasofverylimitedaccessoratthecornersoftheroomtohandscrapethefloor.Thescrapingactionshouldalwaysbeinthedirectionofthegrainwiththesurfacebeinghandsandedormachinesandedwithasmallermachine,i.e.orbitalsander.Withorbitalsanders,toomuchpressureoruseofanoverlyaggressivegradeofpapercanresultindeepswirlmarks,whichwillshowupinthefinish.Onceagain,careneedstobetakentoblendinthesehand-scrapedareaswiththebodyofthefloor.

Thisprocessisrepeatedfollowingthesecondsandingprocess.

Finish sanding

Thefinishsandingoperationinvolvestwoseparatestagesofoperation.

Stage 1 – Initial cutsTheinitialcutsutiliseafinergradeofpaperthanthatusedinthelevelorbasicsandingoperation.Typically,anF60–100gradepaperisusedandthefloorissandedinthedirectionofthegrain(boardrun).Thepurposeoftheinitialcutsistosmoothoffthecoarsesandingmarksleftbythelevelorbasicsanding.Onceasuitablelevelofsmoothnessisachieved,thefinalstageofsandingmaybecarriedout.

Stage 2 – Final sandThefinalsandutilisesanevenfinergradeofpaper–againreducingthedepthofscratchingandpreparingthefloorforthecoatingsystem.Thefloormustbefullycleanedofdust,gritanddebris.Anymatterleftonthefloorwillinvariablyaffectthequalityofthefinish.

Typically,thefinalsandiscarriedoutusingarotarysander,plateorbitalsanderorsimilarmachinewitha100-150gradepaperorscreenback.Thesandingshouldbecarriedoutinthedirectionofthegrainensuringasmoothactionandapplyingabalancedcontrolofthemachine.

Edge sanding requires a smooth action to blend into the floor.

Initial cut.


Ifawater-basedcoatingsystemisspecified,thefinalsandmayneedtobecarriedoutusinganeworworn150meshscreenback(seemanufacturer’srecommendations).Theflooristhenvacuumedthoroughlyand,ifrequired,tackragcleaned.Specialattentionshouldbepaidtoanypotentialdusttrapsinthefloor(digoutanydirtordustandvacuumaway).Thesecancontaminatethefloorcoatingsystemifnotcleanedadequately,astheapplicatorwillmostcertainlypullthedirtontothebodyofthefloor.Itshouldalsobenotedthatheavysandingequipmentmayhavethepotentialtocreatewheelmarksonlow-densityfloorboards.Additionalcareshouldbetakenintheseapplications.

5.4 Coating System Application

Thefollowinginformationisatypicalapplicationmethodology,whichmightbeutilisedforthevariousfinishtypeswithminorproduct-specificvariations.

Cleaning

Thefloorfinishwillbeeasilycontaminatedwithanydirt,dustorotherextraneousmatterleftonthefloor.Itisessentialthattheareabethoroughlycleaned/vacuumed,payingparticularattentiontoanyareaswhichmayhavecaughtdustduringthesandingprocesssuchaswindowsills,picturerails,skirtings,powerandlightswitches,lightfittings,handrails,etc.Thefloorneedstobewelllitwithadequateventilation.Itisimportantnottohavedraughtsblowingacrossthefloorduringtheprocessastheymaywellintroducecontaminatesfromoutsideoftheactualworkingarea.

Mixing the coating

Thecoatingmaterialshouldbethoroughlymixedsothatallthesolidsareblendedthroughthebodyoftheliquid.Careshouldbetakennottostirtooquicklyorroughlyasthismayintroduceairbubblestothematerialwhichaffectsthecoatingquality.Ifthereareanyadditivestobeused,ensuretheyaremixedthoroughlyintothecoatingliquid.Inallcasesfollowthemanufacturers’instructions.

Cutting in

Usingaclean,good-qualitybrush,cutinthefinisharoundtheperimeterwallsandanyotherobstructionsorareaswhichmaynotbeaccessibletothemainapplicator.Thecuttinginshouldextendoutapproximately150mmintothebodyofthefloorsothattheapplicatorisnotrequiredtoventuretooclosetotheskirtingsandotherlimitedaccessareas.Ifanybristlesfalloutofthebrushintothefinish,removeimmediately.

Final sand.

Cutting in the finish around perimeter walls.


Applying coating

Theinitialcoatappliedtotherawsandedtimbermaybeeitherarecognisedsealercoatasprescribedbythecoatingmanufacturerorthesamematerialtobeusedasafinish,exceptwhenoutsidethemanufacturer’srecommendations.Sealersareavailableinbothwater-basedandsolvent-basedproducts.Theuseofasealercanenhancethedevelopmentofcolourinthetimberfloorandcanreducetheriskof‘edgebonding’.Penetratingandlow-rupturesealersareavailable.Inallcasesitisimperativetocloselyfollowmanufacturers’instructions.

Therearemanyapproachesandmethodsusedintheapplicationoffloorfinishesandcoatingsystems.Thefollowingapproachisonesuchapplicationmethod,thathasgenerallybeenacceptedbytheindustry.

Theapplicatorasspecifiedbythecoatingsystemmanufacturer(oftena6mmMohairrollerorequivalent)isimmersedinthecoatingcontainedinalargepainter’strayorapplicatorbucket.Theseallowtheapplicatortobelightlysqueezedontheshallowportionofthetraytoavoiddrips.Theproductshouldbeappliedtotheboardsinasmoothactionstartingatoneendoftheboardsandworkingtheproductinlinewiththegrainofthetimberboards.Thefinishshouldbefeatheredoffattheouteredgetominimiseanybuildupofcoatingatthatpoint.Thisprocessshouldleavea‘wetedge’sothateachsuccessivesectionofapplicationblendsintotheprevioussectionwithoutanyridging,whichcanoccurifthematerialskinsordriesoffbeforethenextapplicationstrip.Theapplicationprocessshouldcontinueinthesamemannerworkingfromoneendoftheareatocompletion.Aneven,wetlookshouldresult,withoutanydrypatches.

Filling/stopping

Itisnotarecommendedpracticetofilltongueandgroovetimberfloors.

Anynailholesnotpreviouslyfilledandanycracksorotheropenfaultsshouldbefilledwithasuitablefillingcompoundthatiscompatiblewiththefinishtype.(Note:ensurethecoatingsystemisdry.)Generally,anon-oil-basedfillerthatissuitablycolour-matchedtothetimberisbest.

Thefillershouldbeinstalledwithacleanbladedapplicator.Ensurethefillerslightlyoverfillstheholeandhasbeenfullypushedintothevoid.Ifthematerialisnotcompletelyfillingthevoid,itmaypotentiallycomelooseinservice.Cleanoffanyfillerthatisspreadoverthefloorsurroundingthehole.Anyexcesswillbesandedawayinthelightsandingbetweencoats.

Sanding between coats

Thefloorwilltypicallyhaveaslightlyroughfeeltoitafterthefirstcoatoffinish,dependingonthesystemusedandthedegreeofgrainraisecreated.Itisnormalformoreopengraintimberstoexhibitahigherdegreeofinitialgrainraisethandenserclosegrainspecies.Thefloorrequiresalightsandafterthefirstcoattoremovethisroughnessandtoalsokeythesurfaceforthenextcoatoffinish.A150orfinergritpaperorscreenbackisusedatthisstagewitharotarysanderorsimilar.Itisimperativethatthesandingdoesnotexposethetimberasthiswillcreatefurtherraisedgrain.Thesandingprocessisrequiredtosmoothofftheroughnessinthecoating,notthetimber.Edgesmustbehandororbitalsandedtoasimilarsmoothness.

Application of the initial coat.


Cleaning between coats

Alldustshouldbethoroughlyremovedfromthefloor,alongwithanypotentialdusttrapsaspreviouslydescribed.Ensurethattherearenodraughtsblowingthroughtheareathatcouldcontaminatethefinalcoat(s).Inaddition,itmaybeprudenttouseatackragoverthefloortoremoveanydustmissedbythevacuum.Thiswillensurethatthefloorisascleanaspossibleforthefinalcoat(s).

Second coat

Thefloorshouldagainbeedgedwithacleanbrushcomingoutsome150mmormoreintothebodyofthefloor.Theapplicationprocessisasperthefirstcoatwiththeapplicatorbeingworkedalongthefulllengthsoftheboardsandlightlyfeatheredattheouteredgeofeachstripofapplication.

Additional coats

Anyadditionalcoatsshouldfollowthesameprocessesofalightsandofthepreviouscoat,thoroughcleaningandapplicationofthecoating.Typically,athree-coatsystemisutilised,howeverallmanufacturers’recommendationsshouldbefollowedinregardstonumberofcoatsandsandpapergrades,inadditiontoanyrequirementsofthespecifier.Variouswater-andoil-basedcoatingsystemsrequireafinergritofpaperbetweencoatsascomparedtothesolvent-basedproducts.

Application of the second coat.


Overall Appearance to be Expected

There are no standards that outline what an acceptable appearance of a timber floor should be. There are standards that relate to the manufacture of timber flooring and when recommended sanding and finishing practices are undertaken, and there is a general level of acceptance of the finished product in the marketplace.

Floorsofthesamespeciescandiffermarkedlyintheirappearancedependingontimbersource,ageofthetree,boardcoverwidth,thefinishsystemusedandthelightinginwhichthefloorisviewed.Timberisanaturalproductthatwillshrinkandswellinresponsetochangesinatmospherichumidity,differencesinthebuildingenvironment,orifthesandingandfinishingisnotundertakeninadust-freefactoryenvironment.Finishesmayalsodarkenwithtime.Evenwiththesevariables,ahighstandardinthefinishedfloorisachievable.

6.1 Acceptable Appearance

Colour, species and grade

Theoverallcolourorblendofcoloursinafloorisdependentonthespeciesorspeciesmixandthecharacterofthefloor.Thefeaturespresentinafloor,suchasgumveins,aredeterminedbythosefeaturespermittedbythegrade.Evenwhenasinglespeciesischosentherecanbeawidevariationincolouranditisalsopossiblethatalimitednumberofboardsofadifferentspeciesmaybepresentduetosimilarityinappearance.Itisalsoimportanttorealisethatgradingrulesdonotcovereithercolourorcolourvariation.GradenamesthatdonotalignwiththeAustralianStandardsarelikelytobesimilartothoseinthesestandardsbutclarificationshouldbesoughtregardingdifferences.

Thegradingprocessisrapidandreliesonquickvisualassessmentwheregradersmustassessthesizeandextentofafeaturewithoutrelyingonmeasurement.Duetothis,someinaccuracyingradingcanoccurthatmayresultinalimitednumberofboardsthatareoutsidegradelimits.Thesandingofafloorcanalsoincreasethesizeofsomefeaturesorcausefeaturestoappearthatwerenotpresentpriortosanding.Consequently,someboardsinafinishedfloormaynotmeetthespecifiedgradedescription.Thepresenceanddevelopmentofsuchfeaturesneedstobeacknowledgedbythosepurchasingtimberfloors.Whenviewingafloor,thereisgenerallyacleardifferencebetweenafloorthatisoftheincorrectgradeandafloorwheregradelimitshavebeenexceededinsomeboards.

Wherethenumberofboardsinafloorthathasfeaturesthatexceedgradelimits,intermsofsizeandnumber,arerelativelyfew(lessthan5%)andtheoverallappearanceofthefloorisinlinewiththechosengrade,noremedialworkisconsiderednecessary.

6A high standard of appearance is achievable.


Gradingalsodoesnotaccountforthedistributionoffeaturesinboards,betweenboardswithinapackofflooringorwithinafinishedfloor.Itisareasonableexpectationthattheinstaller,whenlayingthefloor,willprovidearelativelyevendistributionofcolourandfeaturethroughoutthefloor.Withregardtocolourhowever,itmustalsoberecognisedthatcoatingafloorhighlightscolourdifferencesandtheextentofthechangeisattimesnoteasytodiscern.Similarly,itcanbeexpectedthatboardlengthswillberelativelyevenlydistributedinthefloorandthatgroupsofshortboardsorboardendswillnotbefrequentlyclusteredtogether.

Even timber surface

Thefollowingoutlinessomeproblemsthataffectthesurfaceoftheboardsandtheseshouldnotgenerallyoccurintimberfloors.However,specificheatsourcesfromappliancesorsunexposurethroughlargeuncoveredwindowsmayinducesomecuppingofboardsintheaffectedarea.Similarly,wideboardsorthinneroverlayboardsmayalsoshowsomeslightcuppingorpeakingincertainhouseenvironments.Itshouldalsoberecognisedthattheactionsorinactionofownerscancontributeorevencausethesetooccur.

• Cupping –boardswiththeiredgeseitherhigherorlowerthatthecentreoftheboard.Heatinaspecificlocationoraverydryenvironmentabovethefloormayresultincupping.Moistsub-floorspacescanalsocauseboardstocup.Cuppingismorelikelytobeobservedinoverlayflooringandstandardthicknessboardsthatarewiderthan100mm.Tosomedegreeasmallamountofobservablecuppingmayoccurinsomelocationswithinadwelling(e.g.sunexposedfloor).

•

• Peaking –thishastheappearanceofcuppingbutistheresultofexpansionpressureinthefloor.

• Tenting –twoadjacentboards,wheretheadjoiningedgehasliftedabovetheleveloftheadjacentflooring.Thisisoftenassociatedwithhighmoisturebeneaththefloorandcanbefrommanycauses.

• Buckling –asectionofflooringcontaininganumberofboardsthatisraisedaboveanadjacentsection.

Boards ends should be spaced out and preferably 450 mm or more apart.

Cupping – Board edges higher than the centre of the board, but which is barely visible in the floor.

A select grade Blackbutt floor where the backsawn gum vein toward the top right exceeds grade limits but is acceptable within the floor.


• Crowning –floorboardsthatareflatontheirlowersurfacesbutwheretheuppersurfacehasitsedgeslowerthanthecentreoftheboard.Thismayoccurifaflooriscupped(boardedgesup)atthetimeofsanding.Crowningdoesnotbecomeapparentuntilsomemonthsafterfinishing.

Note:Floorsexposedtoheatsourcesafteroccupancy(e.g.nocurtains,fireplaces,ventsfromappliances,housesclosedupforextendedperiods)maycauseboardstocup.Cuppingandshrinkagefromsuchsourcesmaybetheowner’sresponsibility.)

Relatively even gapping between boards in areas not exposed to specifi c heat sources

Duringdriertimesoftheyear,shrinkagegapsbetweenboardsmayaverage0.75mmforboardsofacoverwidthof80mm.Forwiderboards,proportionallywideraveragegappingcanbeexpected.Somegapswillbelargerthantheaveragegapsizeandotherssmaller,howevertheappearancegenerallyindicatesgappingbetweenmostboards.Anappearancecanbeexpectedthatisfreefromsplitboardsandwidegapsbetweenboardsthatmaybeirregularlyspacedacrossthefloor.Irregularlyspacedwidegappingmayoccurfromeithertheedgesofboardsbeingbondedtogetherorfromaproportionofboardsbeinghighinmoisturecontentatthetimeoflaying.Theprovisionofexpansiongapsaspartoftheinstallationprocessandevidentthroughoutthelifeofthefloorisacceptable.

Limited vertical movement at T&G joints

Flooringismanufacturedwiththeboardtonguenarrowerthanthegroove.Thisisnecessarysothatboardswillfittogetherduringinstallation.Whenfloorboardsarelaidoverjoistsinparticular,somedifferentialverticalmovementmayoccurbetweenadjacentboardswhenaloadisappliedtoanindividualboard.Thisisduetotheclearancebetweenthetongueandthegroove.Theclearanceshouldnotexceed0.6mm.

Minimal squeaking

Asmallamountofnoisecanbeexpectedfrommosttimberfloorswhenwalkedon.Noisescanoccurfrommovementofoneboardedgeagainstanotherorfromboardsmovingonnails.Afloorisoftenmorenoisyduringdrierweatherduetolooseningatthejoints.

Indentations

Timberstripfloorscanbeexpectedtoshowsomeindentationsdependingonthehardnessofthespeciesused,volumeoftrafficandfootwearworn.


A finish with minimal contamination and sanding marks

Afinishsimilartothatoffinefurnitureshouldnotbeexpected.Sandedandpolishedtimberstripfloorsarenotfinishedinafactoryenvironmentanddifferentpiecesofflooringwillsanddifferently.Thehomeenvironmentisalsonotdustfree.However,thefinishedfloorcanbeexpectedtohaveanevenappearancefreefromheavysandingmarks,bloomingorfrequentairbubblesinthesurface.Aminimallevelofcontaminants,minorsandingmarksandsmalldepressionsofthefinishatboardedgesandinnailholes,etc,maybevisible.Theperimeterandotherhard-to-get-atplacesaremorelikelytocontaintheseirregularities.Duetothis,amirrorfinishisanunachievableexpectation.Somefinisheswillalsoyellowwithtimeandifrugsaremoved,acontrastinthedepthofcolourcanbeexpected.

Inspectfloorsforimperfectionsduringdaylighthourswithlightingon.Theoverallassessmentofthefloorisfromastandingpositionwiththefloorviewedfrompositionsthatareusuallyoccupiedbypeople.Internalandexternalreflectionsinareasnotusuallycoveredbyfurnitureshouldbeassessed.Acceptabilityreliesonjudgmentthattakesintoconsiderationtheeffectoflightingonnoticeablesurfaceimperfectionsaswellasinitialwearofthefloor,whichcancausesomeimperfectionstosignificantlylessenordisappear.Afloorissubjecttomuchheavierwearthanfurnitureandalthoughagoodqualityfinishcanbeexpected,thesamefinishqualitytofurnitureshouldnotbeexpected.

Someimperfectionsthatcouldbeexpectedtosomedegreeinafloorbutwhichshouldalsobeassessedinclude:sandingquality;glossvariation;dust,insectsanddebris;bubblesandgelparticlesandcoatlevelling.

The same area of flooring but with downlights on in the right hand photo. Downlights highlight sanding imperfections and dust, some of which can be acceptable.


Care and Maintenance

Timber floors vary in ease of maintenance depending on the type of coating used and the severity of use. They always greatly benefit from regular care. In doing so, the life of the floor finish and floor are greatly enhanced. However, at some stage the floor will need to be rejuvenated and this usually requires buffing back and re-coating.

Someofthesofterfloorfinishescanalsobenefitfromapplicationofmetalisedpolishwhichprovidesanadditionalwearsurface.Itisimportantthatmaintenanceaspectsarepassedontohomeownersasitassistsinensuringongoingcustomersatisfaction.

7.1 A Newly Finished Floor

Althoughafloormaybewalkedonafterinitialcuring,someprecautionsarenecessarywithanewlyfinishedflooruntilthecoatingsystemhasfullyhardenedandthismaytakeintheorderoftwoweeks.Useofthefloorbeforethefullcurehasbeenrealisedcanresultinincreasedtendencyforscuffingandscratching.Itisrecommendedthatrugsarenotlaiduntilafterthefloorfinishhasfullyhardened.Additionally,rugswithrubberbackingsshouldneverbeusedasthesemaytendtostaintheappliedcoatings.Whilelightfurniturecanbereplacedandusedduringthisperiod,itshouldbeensuredthatfurnitureprotectionfeltpadsareattachedtothefeetoftablesandchairs,etc,andfurnituresuchaschairsshouldbelifted.Similarly,itshouldalsobeensuredthatheavyitemssuchasfridgesaremovedcarefullyintopositionandatnotimeshouldtheybedraggedovereithernewlyfinishedorfullycuredfloors.Considerationshouldalsobegiventochairswithcastorsastheycanindentsoftertimbersandalsocauseprematurewearofthecoatingstheyareincontactwith.Again,theseshouldnotbeuseduntilthefinishhashardenedandbarreltypecastorsarelesslikelytodamageafloorthanballcastors.

7.2 Ongoing Care and Maintenance

Ingress of grit and direct sunlight

Thearesomethingsthatareenemiestotimberfloorfinishesandoneoftheseissandorgritthatcanbebroughtintothehousewithfootwear.Thesesmallparticlesactlikesandpaper,resultinginscratchesinthefloor.Matsplacedbothoutsideandinsideexternaldoorsprovideasimpleandeffectivemeansofsignificantlyreducingthegritenteringthehouse.Similarly,inhigh-wearareas,runnersandrugscanbeeffectiveandcanalsoaddtothedécorofthehouse.Thekitchenfloorgenerallyexperienceshighwearandafloorruginthisareacanbeparticularlybeneficial.

Timber floors are easy to maintain and greatly benefit from regular care.

7


Anotheraspectthatshouldbeconsideredistheamountofdirectsunlightthatisreachingthefloors.Directintensesunlightcancontributetogappingandpossiblecuppingofboards.Itwillalsocausethecolourofbothboardsandfinishtochangewithtime.Somefloorfinishesaremorepronetodarkenwithageanddirectsunlightacceleratesthisprocess.Filteredsunlightthroughsheercurtainsorblindsprovidesaneffectivemeansofslowingthecolour-changeprocessesandisalsoeffectiveincontrollinggapsizeandpossiblecupping.Ifthesunlighthasnotbeencontrolledbywindowcoverings,patioroofsorawnings,floorsrugscanbeused.

Maintenance plan

Establishingaregularcleaningprogramwillgreatlyassistinkeepingfloorsinpristinecondition.Therearemanyaspectsthataffecthowoftenthefloorrequirescleaningandtheseincludethedegreeofgritpresent(particularlyfromchildrenandpets),typeofexteriorandinteriormattingused,theleveloftraffic,typeoffootwearandgeneralconditionsoftheareaoutsidethehouse.Spillsshouldbemoppedupwhentheyoccurandanyleaksmustbeattendedtoimmediately.Failuretoattendtoleakingpipeworkcanresultinseveredamagetotimberflooring,particularlywhenlaidoversheetflooringordirectlyadheredtoaslab.Scuffmarksorstubbornstainsmayberemovedwithlightrubbingusingatimberfloorcleaner.Assomecleanerscanattackcertaintypesofcoating,wherepossibleusethecleaningregimespecifiedbythecoatingsmanufacturer.Alternatively,alwaystestrubanisolatedareaoffloortoverifycompatibilityofthecleanerusedwiththecoating.

Forregularcleaningofdomesticfloorsanantistaticmopprovidesaneffectivemeanstocollectdustandgrit.Continualwalkingonadirtyfloorwillquicklydamagethefinish.Ifavacuumcleanerisused,theconditionofthebrushesshouldberegularlychecked.Iftheyhavewornthin,contactofthemetalheadonthefloorcanresultinscratching.Also,donotusehardheadvacuumcleanersastheywillinvariablycausefinescratchesonthefloor.

Steammopsarenotrecommendedonpolishedfloorsastheycandamagecertaintypesofcoatings.

Floorscanalsobenefitfrommonthlydampmopping.Providingthemopisonlydampandthefinishisingoodcondition,moppingcarriedoutcorrectlywillnotaffecteitherthefinishorthetimber.DampmoppingprovidesaneffectivedeepcleanandshouldbeundertakenwithaneutralpHwoodfloorcleanerorproductrecommendedbythefinishmanufacturer.Harshdetergentsorabrasivecleanersaretobeavoidedasisuseofmethylatedspiritsandvinegarastheycanchemicallyattacksometypesofcoatings,e.g.waterbornepolyurethanesandpenetratingoils.Afterwetting,themopshouldbewrungoutuntilitismoist.Usingcleanwater,afinalmoppingwithamopwrungouttillitis‘dry’maybeusedtofurtherremoveexcessmoistureontheboards.Periodically,theprotectivepadsonfurniturelegsshouldbecheckedtoensuretheyarecleanofgritortoseeiftheyneedreplacing.

Re-coating

Timberfloorsaresubjecttodifferentwearpatternsanditisinareasofhigherwearthattherewillinitiallybesignsthatthefloorrequiresre-coating.Itisimportanttoensurethatexcessivewearhasnotoccurredifatotalre-sandandre-finishistobeavoided.Thefinishshouldbeinspectedinthehigh-wearareasandifafewdropsofwaterbeadonthesurfacethenthefinishisstillintactandmayrequirecleaningratherthanre-coating.If,however,afterafewminutesthewaterbeginstosoakinandthetimbercolourdarkens,thenthefinishispartiallywornandre-coatingshouldbeundertaken.

Floor mats at doorways provide a simple means of limiting the amount of grit from entering the home.


Appendix A – Moisture Content and Timber Movement

Water In Wood

Inallcommonapplications,timbercontainsmoisture.Eventimberthathasbeeninservicefor100yearswillcontainsimilaramountsofmoisturetoseasonedtimberthathasjustbeenputintoservice.Thereasonforthisisthatthemoistureintheair(humidity)maintainsacertainlevelofmoistureinthewood.Themoisturepresentinfreshlysawn(i.e.green)timber,straightfromthelog,ismuchhigherandasaconsequenceofthis,theairabsorbsmoisturefromgreentimberuntilabalanceisachieved.

Moisture content

Fortimberproductssuchasflooring,theamountofmoisturepresentoritsmoisturecontentisdefinedasthemassofwaterpresentinthetimberdividedbythemassofthetimberwithallwaterremoved,expressedasapercentage.Themass(measuredingramsorkilograms)ofwaterpresentcanbedeterminedfromthedifferenceinthemassofthetimberwithwater(initialmass)tothemassoftimberwiththewaterremoved(ovendrymass).Thefollowingequationisusedtodeterminethemoisturecontentoftimber:

Thestructureofthecellsintimbercanbelikenedtoanumberofdrinkingstrawsgluedtogether.Ifthestrawswerefullofwateritcouldbeexpectedthatthemassofwatercontainedinthestrawswouldbegreaterthanthemassofthedrinkingstrawsalone.Insuchacasethemoisturecontentascalculatedabovewouldexceed100%.Inatreethemoisturecontentmaybeaslowas40%butcanbeashighas180%.Greenoff-sawtimbercouldhavemoisturecontentsof180%,whichmeansthetimbercontains1.8kgofwaterforevery1.0kgofdrytimberthatwaspresent.InsoftwoodssuchasRadiataPineandAraucariatheaveragemoisturecontentsof180%ormoreoftenoccur.Inmanyofourcommonhardwoodsthemoisturecontentmaybenogreaterthan70%.Cypress,asoftwoodthatgrowsindrierareas,mayonlyhaveaveragemoisturecontentsof45%.Therecanalsobesizeablevariationsinmoisturecontentbetweentheoutersapwoodofatreetotheinnerheartwood.

The Drying of Timber for Flooring

Seasoningordryingistheprocessbywhichmoistureisremovedfromtimberandgreen(i.e.freshlycutboards)maybeeitherairdriedorkilndriedoracombinationofboth.Thedryingprocessforflooringoftenincludesmorethanonestage.Timberisinitiallystackedtoallowairmovementbetweeneachlayeroftimberandinthisstateitcanbeeitherairdriedbyleavingitoutintheopenforsomemonthsorplacedinalowtemperaturepre-dryertogentlyreduceitsmoisturecontentundercontrolledconditions,priortodryingbeingcompletedathighertemperaturesinakiln.Somehardwoodsarekiln-driedfromgreenbutmanyoperationsuseinitialairdryingorapre-dryerfollowedbykilndrying.Softwoodsaregenerallyair-orkiln-driedfromgreen.

A

% mc = “mass of water present “ x 100% “oven dry mass”

= “initial mass” - “oven dry mass” x 100%

“oven dry mass”

#09 • Timber Flooring Design Guide Page 52#09 • Timber Flooring design guide

Whenwerefertoseasonedtimber,weareusuallyreferringtotimberthathasmoisturecontentsfrom9%to14%.ThisrangehasbeenchosenbecausetimberincoastalAustraliawillusuallyremainwithinthismoisturecontentrange,whenusedinternally.Whethertimberisdriedbytheairorinakilnthereisalwaysasmallvariationinthemoisturecontentsofindividualboards(usuallyabout5%).Duetothesevariations,someboardswilltakeupmoisturefromtheairafterbeingputintoservice,whileothersmaylosemoisture.Whentimbertakesupmoistureitexpandsandwhenitlosesmoistureitshrinks.Thesmallmoisturevariationspresentatthetimeofflooringmanufacturethereforetranslateintosmalldifferencesinboardwidthsasboardmoisturecontentsadjusttobeinbalancewiththehumidityintheair.

Movement in Timber with a Change in Moisture Content

Waterinwoodresidesbothwithinthe‘straws’(calledfreewater)andinthewallsofthe‘straws’(boundwater).Asindicatedabove,themoisturecontentinlivingtreeswillvarygreatlydependingonthespecies,ageofthetreeandlocationinwhichitisgrown.However,nomatterwhattheinitialmoisturecontentisofthewoodinthetrees,shrinkageintimberisminimaluntilthemoisturecontentreachesapproximately25%.Atthislevelmuchofthefreewaterhasbeenremovedanditisfromthispoint(calledthefibresaturationpoint)thattherebecomesasignificantreductionintheboundwatertiedupinthecellwalls.Associatedwiththis,thecellwallsbegintoshrinkandweobserveshrinkageintimber.Thisrelationshipisshowndiagrammaticallyinthegraph.

Withinthesawmillingindustry,boardsarereferredtoasbeingeitherbacksawnorquartersawn(seeimageabove)andthemovementcharacteristicsofeachisquitedifferent.Inabacksawnboardtheangleofthegrowthringsontheendsectiontothewidestfaceislessthan45°.Inquartersawnboardsthisangleisgreaterthan45°.Backsawnboardsareoftenvaluedforthe‘figure’thatappearsonthesurfaceofthetimberflooringandwithbacksawingtheamountofusabletimberrecoveredfromthetreeisalsousuallygreater.However,backsawnboardscanbeexpectedtoshrinkinwidthmorethanaquartersawnboardandduetotheangleofthegrowthrings,backsawnboardswillhaveaninherenttendencytocupwhentheydry.

Backsawn and quartersawn fl oor boards.


Theamountofshrinkagethatoccursradially(i.e.inadirectionthatradiatesoutfromthecentreofthelog)differsfromthatoccurringtangentially(atrightanglestotheradialdirection).Therefore,inabacksawnfloorboardthecoverwidthwillvaryasaresultoftangentialmovementandinaquartersawnfloorboardthecoverwidthwillvaryfromradialmovement.FlooringmanufacturedfromspeciesgrowninTasmaniaandVictoriaareoftenquartersawn,whereasspeciesfromQueensland,NewSouthWalesandWesternAustraliaarepredominantlybacksawn.

Ausefulmeasureofmovementiswhatistermedthe‘unittangentialmovement’(UTM).Thisisthepercentagedimensionalchangeforeach1%changeinmoisturecontentbetween3%andthefibresaturationpointfortheparticularspecies.Forexample,BrushBoxhasaUTMof0.38.A3%increaseinmoisturecontentcouldonaveragebeexpectedtocausean80mmwidebacksawnfloorboardtoincreaseinsizeby:

0.38 x 3% x 80/100 = 0.9 mm

Whendealingwithseasonedtimber,theUTMcanbeusedtoestimateanticipatedmovement,howeveractualmovementisoftenlessthantheestimate,duetothepresenceofquartersawnmaterialandwithregardtoapplicationssuchasflooring,somecompressionofthetimberoftenoccurs.Careisnecessarywhenapplyingthesefigures.TablesofUTMareavailablefromstatetimberorganisations.

Flooring response to changes in humidity

Arelationshipexistsbetweentheairtemperature,relativehumidityoftheairandthemoisturecontentthattimberwilltrytoattain.Thisrelationshipisshowninthefollowingchartanditcanbeseenthathumidityhasthepredominantinfluenceovermoisturecontent.Asanexample,iftimberisinaroomat25°Candtherelativehumidityis65%thenthetimberwill,intime,trytoreachapproximately12%moisturecontent.

Obviously,humidityandtemperaturewillchangeonadailybasisaswellasonaseasonalbasis.Becauseoftimber’srelativelyslowresponserate,weareusuallymoreconcernedwithseasonalchanges.Theeffectsofseasonalchangesmaybeobservedinapolishedtimberfloorbytheopeningandclosingofgapsbetweenadjoiningboardsatdifferenttimesoftheyear.

Weatherdataprovidesinformationonthechangesinrelativehumiditythatcanbeexpectedinaparticularlocalityandthisisparticularlyimportantifinstallingafloorinalocationthatdiffersfromtheonethatyouareusedto.Therecanbesignificantchangesovershortdistances,forexample,betweenacoastalcityandhillyruralenvironment,ahalfhour’sdriveaway.Examplesofdifferentclimates,seasonalhumidityfluctuationsandaveragemoisturecontentsaregiveninthegraphsbelow.

Temperature, relative humidity (RH) and equilibrium moisture content (EMC).

Climatic effects on timber floors.


Althoughthesegraphslinktimbermoisturecontenttosurroundingenvironmentalconditionstheydonotshowtheresponserateofdifferentspeciestothesechangingconditions.TheresponserateofsoftwoodssuchasHoopPineorRadiataPineismorerapidthanthatofthedenserhardwoodssuchasSpottedGum.However,evenwithinthehardwoodorsoftwoodgroups,responseratescanalsovaryquitemarkedly.IndicativeresponsecurvesfromonetrialforSpottedGumwhenplacedinaveryhumidenvironment(18%EMC)followedbyadryenvironment(8%EMC)isshowninthegraphsbelow.Thefirstgraphshowsmoisturecontentchangesandthesecondgraphthechangeincoverwidth.Clearlythisillustratesthevariabilitythatcanbepresent.Blackbutt,althoughadensehardwood,takesupandlosesmoisturequiterapidly.

Thespeciesthatmorequicklytakeuporlosemoisturewillgenerallyfollowseasonalchangesmoreclosely.Thegraphsalsoindicatethattherateofmoistureuptake,whichmayresultfromarelativelyquickandsustainedchangeinweatherconditions,caninitiallybequiterapidbuttherateofincreasethenslowsovertime.Thisaspectisalsoreflectedintimberfloors.Floorinstallerssometimescommentthatafloormayhaveshrunkalotinthefirstweekorsoafterlayingbutthatithadn’tmovedmuchsincethen.

Asaguide,thetablebelowoutlinesthedensityofthespecies,whethertheflooringispredominantlybacksawnorquartersawnandanindicativemeasureofthespeciesresponseratetomoistureuptakeandloss.Inlocationswherefloorsarelikelytoexpandafterinstallationparticularcareisnecessarytoadequatelyaccommodatetheexpansionthatwilloccur(i.e.intermediateexpansionjoints,looselayandacclimatisation).Thisisparticularlysowithhigherdensitytimbersandparticularlythosethatrespondquicklytoseasonalhumiditychanges.

Results from the FWPRDC Research on Timber Flooring undertaken by Timber Queensland Ltd. The graphs show averages of ten pieces of Spotted Gum flooring from different sources placed in a conditioning chamber at 18% EMC for 21 days followed by 8% EMC for 21 days.


Appendix B – Measuring Moisture Content of Timber and Sheet ProductsCheckingthemoisturecontentoftimberflooringpriortoinstallationisimportanttoprovideacheckontheproductsupplied,evaluatetheneedforadditionalexpansionallowanceandtoensurethatsubsequentmovement(shrinkageandswelling)remainswithinacceptedbounds.Thisappendixoutlinesthevariousmethodsusedtotestthemoisturecontentoftimber.Alsoincludedintheappendixisamethodtoevaluatethemoisturecontentcomplianceofpacksofflooring.

Moisture Content Measurement

Moisture content

Moisturecontentissimplythemassofmoisturepresentinwooddividedbythemassofthewoodwithnomoistureinit,expressedasapercentage.What’simportantaboutthemoisturecontentintimberisthattheboardwidthwillincreasewithincreasingmoisturecontentandwilldecreasewithdecreasingmoisturecontent.Atthetimeofmachining,coverwidthvariationsareusuallyminimalandsubsequentvariationsinboardwidthsareusuallyduetochangesinmoisturecontent.Itisoftenthecurrentandfuturevariationsinboardwidththatareofprimaryimportanceandoneimportantpurposeofmoisturecontenttestingistoindicatewhatfuturemovementcanbeexpected.

Bysimplylookingattheendofapackofflooringthatmaybeamonthorsoolditisoftenpossibletoobtaininformationaboutthemoisturecontentofthetimberwithinthepackevenwithoutusingamoisturemeter.

Forexample,inathree-month-oldpackofflooring,somemoisturechangesarelikelytohaveoccurred.Ifthenominalcoverwidthis80mmand:

• ifboardwidthsarebetween,say,79.6mmand80.4mm,thenthematerialislikelytohavebeendriedtowithinnarrowmoisturecontentboundsandshouldperformwellinservice.

• ifboardwidthsrangefrom,say,78mmto81mmandsomeboardsarecupped,thenthematerialislikelytohavebeendriedtoquitewidemoisturecontentboundsandthefloorislikelytoshowsomewidegapsatboardedgesalongthelengthoftheboardandnearendmatchedjoints.

• ifboardwidthsrangefrom,say,80mmto84mm,thensomeofthematerialmayhavebecomewetaftermanufacture.

Itisimportantwhenconsideringmoisturecontenttoalsotaketheboardwidthsintoconsideration.AustralianStandardsthatcoverthemoisturecontentofflooringvaryintheirlimitsasthisdependsonthespecies.

B

Initial mass – 32.63 gOven dry mass – 29.49 g MC = 32.63 – 29.49 x 100% = 10.65% 29.49


Thetablebelowprovidessomeinformationonspeciestypes,thenumberoftheapplicableStandardandthemoisturecontentrangesapplicabletoflooring.

Species Group Moisture Content Bounds Number of the (moisturecontentanywherewithinaboard) applicable Standard

Hardwood 9%to14% AS2796

Softwood 9%to14% AS4785

Cypress 10%to15% AS1810

Methods of Measuring the Moisture Content of Timber

How moisture content is measured

Moisturecontentisgenerallymeasuredbyeitherameterorthroughovendrytesting.Thetwocommontypesofmetersinusearetheresistancemeterandthecapacitancemeter.Metersusechangesinelectricalpropertiescausedbythewoodandwaterwithinittoprovideanestimateofthemoisturecontent.OvendrytestingrequiresasetofscalesandanovenThemoisturecontentisdeterminedfromthechangeofmassasthesampledries.

Measurements by different methods

Inanypieceofflooringthemoisturecontentislikelytovarytosomeextentdownthelengthofthepieceandfromtheoutersurfaces(case)tothecentre(core).Withregardtocase-to-coredifferencessomemethodsofmeasurementareabletomeasurethiswhileotherscanonlymeasuretheaveragemoisturecontentoftheboard.Thiscanbeanimportantconsiderationwhenchoosingameasuringmethodascase-to-corevariationsorthedifferencebetweenupperandlowercasemayneedtobedetermined.Atothertimesitmaybeimportanttogainmanymeasurementsquicklyinordertogainanappreciationoftheaveragemoisturecontent.Incasesofdispute,accuracymaybeofprimeimportance.

Resistancemetersmeasurethehighestmoistureacrosstheexposedendsofthepinswhereascapacitancemetersmeasureanaveragethroughthepiece.Ovendrytestingmeasurestheaveragemoisturecontentofthesampleplacedintheovenbutbycuttingthesampleupintoapplicablesmallerpieces,caseandcoremoisturecontentscanalsobedetermined.

Thethreecommonmethodsofmeasurement,includingtheirapplication,benefits,limitationsandaccuracyareoutlinedonthenextpage.

Capacitance moisture meter measures average moisture content. Need to set species density.

Resistance moisture meter – measures moisture content between the pins. Need to correct reading for temperature and species.

Oven dry testing provides the most accurate moisture content test.


Oven Dry Method

When is it used?

• Ovendrytestingisoftencarriedoutwherevariationsinmoisturecontentinthefinalproductcanhaveasignificanteffectontheperformanceoftheproduct.

• Itisusedwhereaccurateresultsarerequiredormeterreadingsareknowntobeinaccuratewhichcanincludesometimberspeciesbutalsoparticleboardandplywoodsub-floors.

• IncaseofdisputesAustralianStandardsgenerallyrefertothismethodasitprovidesmeasurementsthataremoreaccurateandreliable.

• Manufacturersofboardproductsoftenundertakeovendrytestinginthemanufactureoftheirproducts.

• Sometimberorganisationsalsohavetheappropriatetestingequipmentandcontractouttheseservices.

Testing equipment and facilities

• Theequipmentrequiredisanaccuratebalanceorsetofscalesandalaboratoryoventhatisabletomaintainatemperatureof103°C±2°C.

Sampling from a pack

• Thesamplesneedtoberepresentativeofthetimberinthepackbeingtestedandcapturethevariationpresent.Thismayincludesomeoutsideboardsaswellassomefromwithinthepack.

• Ifcuppingispresentorthereisvariationinthecoverwidthbymorethan1mm,samplesshouldbeprovidedwhichincludetwoboardsthatarecupped,twowithwidercoverwidthsandtwowithnarrowercoverwidths.(Packingpiecesarenottobeprovidedassamples.)

• Ifboardsarenotcuppedandthereislittlevariationincoverwidththroughoutthepack,fiveboardsshouldbechosen.(Packingpiecesarenottobeprovidedassamples.)

• Thesamplesfromwhichtestpieceswillbecutshouldbetakennotlessthan400mmfromtheendofaboardandshouldbeapproximately300mmlong.

Note:Ifthesampleisfromaboardonthetop,bottomoredgeofthepack,itshouldbemarkedasbeinganoutsideboard.

• Thesamplesshouldbeindividuallywrappedin‘GladWrap’orsimilartoreducemoisturecontentchangesduringtransport.

• Thesamplesshouldbestoredinacoolplaceanddeliveredtothetestingfacilitywithin24hours.

Testing Procedure

• Fromthe300mmlongpacksamples,testpiecesarecutwithalengthbetween15mmand30mmsothattherequiredmassisachievedtosuittheaccuracyofthemass-measuringequipment.Iftheequipmentmeasuresto0.1gthenatestsampleofatleast50gisrequired.Thesamplemaybelessthan50giftheequipmentmeasuresto0.01g.

• Theinitialmassesofthetestpieces(andusuallythecoverwidths)arerecorded.Thetestpiecesareplacedintheovenforatleast24hoursandthenreassessedatfour-hourintervalsuntilthereisminimalchangeinmass.Forlongersamplesindenserspeciestimesof48hoursorsomayberequired.Themassafterdryingintheoven(i.e.ovendryweight)isrecorded.

• Themoisturecontentisthencalculatedforeachtestpiecebyapplyingthefollowingequation: Moisturecontent(%)=((Initialmass–ovendrymass)/ovendrymass)x100%Forexample,iftheinitialmassis57.6gandtheovendrymassis43.3gthen themoisturecontentis:Moisturecontent(%)=((57.6g–49.3g)/49.3g)x100%=16.8%

• Thismethodprovidestheaveragemoisturecontentforthetestpieces.Caseandcoremeasurementscanbeobtainedbycuttingtheappropriatesectionsoutoflargertestpiecespriortotesting.

Page 57#09 • Timber Flooring design guide


Interpreting results

• Thesamplingmethodoutlinedaboveaimstocapturethevariationpresentinapackoftimberandfromthisitcanbeassumedthatmostofthetimberwithinthepackwillfallwithintheupperandlowermoisturecontentmeasurements.

• Inapplicationswherecoverwidthisimportant,boththecoverwidthandthemoisturecontentshouldbeconsidered.Oftenboardsoflowercoverwidtharealsothoseofhighermoisturecontentandfurthershrinkageofthismaterialcanbeexpected.

Benefits and limitations

• Themainadvantageofthismethodisitsaccuracy.

• Themethodistimeconsuming,notportableandmoreexpensive.

• Themostcommonerrorresultsfrominsufficientdrying,whichunderestimatesthemoisturecontent.Ifsamplemassesaresmallthenmeasuringerrorscansignificantlyaffectthemoisturecontentcalculation.

• Microwaveovenscanproducegoodresultsandspeeduptesting,howevertherearenoformalproceduresandthereistheriskofevaporatingvolatilecompoundsinadditiontothewaterwhichaffectsaccuracy.

Resistance Meter

Principle of operation

Theelectricalresistanceoftimberreducesasthemoistureintimberincreases.Thesemetersmeasuretheflowofelectricitybetweentwopinswherethetimberactsasanelectricalresistorbetweenthepins.Thescaleonthemoisturemeterisgraduatedtoreadmoisturecontent.Woodtemperatureaffectsthereadingsandforthisreasonwoodtemperatureaboveorbelow20°Crequirescorrectiontothereading.Temperaturecorrection,ifnotalreadytakencareofbythemeter,isappliedbeforespeciescorrection.Speciescorrectionisnecessaryastwodifferenttimberspeciesatthesamemoisturecontentmaynothavethesameelectricalresistance.MetersaregenerallysetuprelativetoonespeciesandthatisDouglasFir(Oregon)andspeciescorrectionsarethenappliedforotherspecies.Therecomesapointwherethewaterintimberissolowthattheresistanceisdifficulttomeasureaccurately,orontheotherhandissufficientlyhighthattheresistancedoesnotchangegreatlyandispronetogreatererrors.Thesemetersgenerallyprovidereliableresultsbetween6%and25%moisturecontent.

Types of meters

Awidevarietyofmetersisavailable.Allhavetwopinsthatareusedtopenetratethetimberbutthepinsmayvaryinlengthfromabout6mmupto50mm.Thelongerpinsareofteninsulateduptothepointedendstopreventsurfacemoistureeffectsfrominterferingwithcoremeasurements.Thosewithlongerpinsarealsousuallyofthe‘slidinghammer’type,whichprovidesameansofdrivingthepinsintothetimber.Thesophisticationofthemetersvariesgreatlyintermsoffeaturessuchasin-builttemperaturecorrection,preprogrammedspeciescalibrationanddepthindication.Manyofthemetersnowcomewithacalibrationblock.

Using resistance meters

• Thecalibrationofthemetershouldbecheckedpriortouseandthisisusuallydonewithatestblockthatcontainselectricalresistorsthatcorrespondtothemoisturecontentsspecifiedonthetestblock.

• Measurementsarethentakenincleartimberatleast400mmfromtheendsofboards.

• Somemetersrequiremeasurementstobetakenwiththepinsrunningdownthelengthoftheboard,whilewithothersthepinsaretorunacrossthewidthoftheboard(checkwiththemanufacturer’smanual).

• Thepinsaredriventothedesireddepthtowhichthemoisturecontentreadingisrequired.Ascaseandcoremeasurementscanbesignificantlydifferent,useofmeterswithshortpinsmayrequireboardstobecutandthepinsinsertedintheendgraintoprovideabetterestimate.Inhighdensitytimbers,holesmayneedtobedrilledforthepins.

• Thepinsneedtobeinfirmcontactwiththetimber,otherwiselowreadingsmayoccur.

• Readingsshouldberecordedtothenearest0.5%andreadshortlyafterpenetration.

• Eachreadingistobecorrectedforwoodtemperaturefirst(providedthisisnotdoneautomatically)andthenforspecies(providingthespecieshasnotbeensetonthemeter).


• RefertoTableB.1fortemperaturecorrectionfactorsandspeciescorrectionfactorsforsomecommoncommercialspecies.AdditionaltemperatureandspeciescorrectionfactorsareavailableinAS1080.1.

Limitations, accuracy and precautions when using resistance moisture meters

Whenusingmeters,acommonsenseapproachisnecessaryandeachreadingshouldbeevaluatedandifnotasexpected,thenthereasonsforthisshouldbeinvestigated.Themetersgenerallyprovideareasonableestimateofthemoisturecontentto±2%inthemeasuringrangefrom8%to25%andasstatedabovereadingsshouldberecordedtothenearest0.5%.Thereareanumberoffactorsthatareknowntoaffectmeterreadingsandtheseare:

• Measurementnecessitatesdamagingthesurfaceofthetimber.

• Themethodisconducivetoonlytakingarelativelysmallnumberofsamplereadings.

• Readingsneartheboardsurfacecanbesignificantlydifferentfromthecore.

• Lowbatterycancauselowreadingsinhighmoisturecontentmaterial.

• Uncertaintyoverspeciestheyarebeingusedincanmakespeciescorrectionsdifficult.

• SpeciessuchasBrushBoxhaveveryhighspeciescorrectionfactorsandarepronetogreatererror.

• Useforextendedperiodsinhighhumidityenvironmentscanraisemeterreadings.

• Metersonlyreadthewettestpartthattheexposedsurfacesofthepinsareincontactwith.

• Surfacemoisturecanprovideartificiallyhighreadingsnotreflectingwoodmoisturecontent.

• Saltwateroranypreservativetreatmentsaltscanaffectmeterreadingsandwillusuallyraisethem.

• Electricalwiringinwallscanaffectthereadings.

• Ifmeterreadingsarenotinlinewithwhatisexpected,thismaynecessitateovendrytestingtomoreaccuratelyestimatethemoisturecontent.

Capacitance Meter

Principle of operation

Thesemetersmeasureanelectricalpropertycalledthe‘dielectricconstant’andinsodoinganelectricfieldproducedbythemeterandthepresenceofthetimberonwhichthemeterispositioned,forma‘capacitor’typeofarrangement.Theelectricfieldcanpenetratedeepintothetimberbutmeterreadingsarebiasedtowardmoistureinthesurfacelayers.Boththemoisturecontentandthedensityofthetimberaffectthiselectricalproperty.Theeffectiverangeofcapacitancemetersisfromapproximately0%to30%moisturecontent.Themoresophisticatedmeterscanbeadjustedfortimbersofdifferentdensities.Lessexpensivemetersdonothavedensitycompensationandforthesemeterscorrectionstometerreadingsmustbeappliedbasedonthedensityofthespeciesbeingtested.Suchmetersareusuallypresettobemoresuitedtosoftwoodsandlowerdensityhardwoodsandthiscancauselimitationswithhigherdensityspecies(i.e.largecorrectionfactorsarenecessary).

Types of meters

Metersareimportedfromoverseasandrangefromthosewithfewfeaturestothosewithawiderrange.Featuresmayincludesettingsfortimberdensity(orspecificgravity)andtimberthicknessaswellastheabilitytostorereadingsandapplysomestatisticstotheresults.Itisnecessarytoensurethatthemeterisgoingtomeetyourspecificneedsandifbeingusedwithhigherdensityhardwoodsthentimberdensity(orspecificgravity)adjustmentmustbeseriouslyconsidered.

Using capacitance meters

• Theappropriatemetersettingsfordensityandboardthickness,etc,shouldbeappliedandthemetercheckedforcalibration.

• Thedensity(specificgravity)isoftencalculateddifferentlyfordifferentreasons(i.e.greendensity,densityat12%moisturecontentorbasicdensity).Specificgravityisthedensityofamaterialdividedbythedensityofwater(about1000kg/m3).Itisnecessarytoobtainfromthemetersuppliertherelevantfiguresapplicabletothemeterbeingused.TableB.2providesdensitiesat12%moisturecontent.

• Measurementsarethentakenincleartimberawayfromknots,etc.

• Somemetersrequiremeasurementstobetakenwiththemeterinaparticularorientationontheboard(checkwiththemanufacturer’smanual).

• Theplateofthemetermustbeinfirmcontactwiththeboardbeforeareadingistaken.

• Readingsshouldberecordedtothenearest0.5%.Ifnodensity(specificgravity)settingsareavailablethenthesemeterreadingsneedcorrecting.


Limitations, accuracy and precautions when using capacitance moisture meters

Similartoresistancemeters,commonsensemustprevailwhenusingthesemeterswithreadingsevaluatedandinvestigatedifnotasexpected.Providingthedensityisaccuratelyassessedthenthesemetersalsoprovideareasonableestimateoftheaveragemoisturecontentinaboarduptoabout25%moisturecontent.Againthereareanumberofaspectsthatneedtobeconsideredwhenusingthesemeters:

• Readingscanbetakenveryquicklybothwithinaboardorinanumberofboards.

• Themetersdonotdamagethesurfaceofthetimberthatisbeingmeasured.

• Withinspeciesdensityvariationscanbequitehigh,particularlybetweenmatureandyounggrowthmaterial.

• Estimatingthecorrectdensityadjustmentcanbedifficult,particularlyifthemeterisbeingusedonawiderangeofdifferenttimbers.

• Density(specificgravity)informationforAustralianspeciesrelatingtospecificmetersisnotwelldocumented.

• Difficultieswithsettingdensity(specificgravity)adjustmentoftenreducesfieldmeasurementaccuracy.

• Ifnotimberthicknessadjustmentisprovidedthenthickerpiecesatthesamemoisturecontentarelikelytoreadhigh.

• Anygapbetweenthemeterandtheboard(e.g.acuppedsurface)willcauselowerreadings.

• Framingraisesmeterreadingswhereexposedtimberscross(e.g.softwoodflooroverhardwoodjoists).

• Thepresenceofsalts(eitherfromsaltwaterorpreservationtreatment)willcausereadingstobehigher.

• ReadingsalsoconsideredtobelessreliablewithBrushBox.

• Again,ifmeterreadingsarenotinlinewithwhatisexpected,thismaynecessitateovendrytestingtomoreaccuratelyestimatethemoisturecontent.

Assessing timber moisture content for conformity

AustralianStandard1080.1–Timber–MethodsofTest–Method1:Moisturecontentoutlinesaprocedureformoisturecontentacceptancetestingoftimberusingaresistancemoisturemeter.Forfulldetailsthestandardshouldbereferredto.Providedbelowisasummaryoftheprocedure:

• Sampleatleastonepackoutofeverytenoronepackoutofeveryfiveforhighervalueproducts(e.g.flooring).

• Foreachpackassessed(ofupto200boardsperpack)15boardsarerandomlyselectedandtested.

• Thepackisdeemedtocomplyifnotmorethanonetestresult(afterapplyingtemperatureandspeciescorrectionfactors)isoutsidetheallowablerange.Thisisprovidingtheresultoutsideallowablelimitsisnottoodifferentfromotherresults.

• Thissamplingprocedureisbasedonatleast90%ofthesamplesfallingwithintheallowablerange.

Measuring the moisture content of plywood and particleboard

Metersdonotprovideanaccurateandreliablemeasureofmoisturecontentinthesematerials.Todeterminethemoisturecontentofthesematerials,theovendrymethodshouldbeused.

Table B.1: Temperature correction factors for resistance moisture meters. (Note: This is wood temperature not air temperature.)

Meter reading % 8 % 10% 12% 14% 16% 18% 20% 22% 24%

Wood Temperature Temperaturecorrectiontobeaddedtoorsubtractedfrommeterreadingbeforeapplyingthespeciescorrectionfactor

15 °C Nil Nil +1 +1 +1 +1 +2 - -

20 °C Nil Nil Nil Nil Nil Nil Nil Nil -

25 °C -1 -1 -1 -1 -1 -1 -1 -1 -

30 °C -1 -1 -1 -2 -2 -2 -2 -2 -2


Table B.2: Species correction factors for resistance moisture meters.

Meter reading % 8 % 10% 12% 14% 16% 18% 20% 22% 24% Density

Species ResistancemetersaregenerallycalibratedtoOregon(DouglasFir).Applythefollowingspeciescorrectionsaftertemperaturecorrection.

At 12% MC

Oregon(DouglasFir) 0 0 0 0 0 0 0 0 0 550

Australian Hardwoods

Yellow Stringybark(NSW) +4 +4 +3 +3 +2 +2 +1 +1 0 900

Red Ironbark Broad Leaved & Red (NSW) +4 +3 +3 +3 +2 +2 +2 +1 +1 1100

Grey Ironbark (Qld) +3 +2 +2 +2 +2 +2 +2 +2 +1 1105

Forest Red Gum – Blue Gum (Qld) +3 +2 +2 +2 +2 +1 +1 +1 0 1000

White Mahogany – Honey Mahog.(Qld) +2 +2 +2 +2 +2 +2 +2 +2 +2 1000

River Red Gum (Vicregrowth) +2 +2 +2 +2 +2 +2 +2 Nodata Nodata 900

Rose Gum – Flooded Gum (Qld&NSW) +2 +2 +2 +1 +1 0 0 0 0 750

Sydney Blue Gum (NSW) +2 +2 +1 +1 0 0 -1 -1 -1 850

Blackbutt (Qld&NSW) +1 +1 +1 +1 +1 +1 +1 +1 +1 900

Turpentine (Qld&NSW) +1 +1 +1 +1 +1 +1 +1 +1 0 950

Blackbutt (NSWregrowth) +1 +1 +1 +1 +1 0 0 0 Nodata 900

Grey Ironbark (NSW) +1 +1 +1 +1 0 0 0 0 0 1100

Red Ironbark Narrow Leaved (Qld) +1 +1 +1 0 0 0 0 0 0 1090

Blackwood(Tas) +1 +1 0 0 0 -1 -1 -2 -2 640

Myrtle(Tas) +1 +1 0 0 -1 -1 -2 -2 -2 700

Spotted Gum (QldCitridora) +1 0 -1 -1 -2 -3 -3 -4 -5 1100

Shining Gum (Vic) +1 0 0 0 0 0 0 -1 -1 700

Jarrah (WAregrowth) 0 0 +1 +1 +1 +1 +1 +1 Nodata 780

Grey Gum (Qld&NSW) 0 0 0 0 0 0 0 0 0 1050

Tallowwood (Qld&NSW) 0 0 0 0 0 0 0 0 0 1000

Alpine Ash(Vic&Tasregrowth) 0 0 0 0 0 0 -1 -1 Nodata 650

Mountain Ash (Vic&Tasregrowth) 0 0 0 0 0 0 -1 -1 Nodata 650

Messmate (Vic&Tasregrowth) 0 0 0 0 -1 -1 -1 -1 -2 750

Southern Blue Gum (SAplantation) 0 0 -1 -1 -1 -2 -2 -3 -3 700

Spotted Gum (NSWRegrowthMaculata) 0 -1 -1 -2 -3 -4 -5 -5 -6 1100

Brush Box (Qld&NSW) 0 -1 -2 -3 -4 -5 -6 -8 -9 900

Manna Gum – Satin Ash (NSW) -1 -1 -1 -1 -2 -2 -2 -2 -3 800

Imported Hardwoods

European Beech +3 +3 +3 Nodata Nodata Nodata Nodata Nodata Nodata 690

Kwila / Merbau (Malaysia) +2 +2 +2 +2 +1 +1 +1 +1 +1 850

Sugar Maple(NthAmerica) -1 0 +1 +1 +1 +1 +1 +1 Nodata 740

Softwoods

Araucaria – Hoop Pine(Qld&NSW) +3 +2 +2 +2 +1 +1 +1 0 0 550

Radiata Pine(Vic) +2 +2 +2 +2 +2 +2 +2 +2 +2 550

Cypress(Qld&NSW) +2 +1 +1 +1 +1 +1 +1 0 0 700

Notes: No correction factors are published for Gympie Messmate, New England Blackbutt or Northern Box. Oven dry testing is the preferred method for Brush Box. Table only contains some common species – refer to AS 1080.1 and FWPRDC report PN01.1306 for a more complete list. The tabled figures are based on the Deltron Moisture Meter. Figures may differ for other meters – refer FWPRDC report PN01.1306 ).


Appendix C – Slab Moisture Assessment

Properties of Moisture in Concrete

Concreteisaporousmaterialthatisabletoholdwaterandwatervapourinsmallvoidsorporeswithinitsstructure.Similartothecellsintimber,theporescanbesaturatedandfullofwaterormoisturecanalsoexistinsidetheporesasavapour.

Itispossibletodeterminethemoisturecontentofconcretebytheovendrymethod,similartotimber,butwithconcreteitisalsopossibletodeterminethequantityofmoisturevapourheldwithintheporesbymeasuringrelativehumiditywithinaslab.

Anothersimilaritytotimberisthatwatervapourwillmoveinandoutofconcretedependingonatmosphericconditionsandtherelativehumiditywithinaslabwillremainquitehighuntilthewaterintheporeshasevaporated.Atthispointthemoisturecontentoftheconcreteisnear2%.However.whenconcreteisnearsaturationthemoisturecontentisonlyabout5%orso.

Referringtothegraphaboveitisapparentthatoncebothtimberandconcretehavelosttheir‘freewater’frominsidetheircellsandporesthenunderconditionsof75%relativehumiditytimberattainsamoisturecontentofapproximately14%andconcreteabout2%.

Whenconcretecures,ahydrationreactionoccursthatusesupmuchoftheaddedwater,however,evenaftercuringtheporeswillcontainasignificantamountofwater,similartothewaterwithinthecellsofaboardthathasbeenfreshlycutfromatree.Inbothcases,itisfromherethatdryingbeginswiththelowerrelativehumidityairofthesurroundingscausingevaporationfromthesurfacesandthiscontinuesuntilthe‘equilibriummoisturecontent’isachieved.Similarly,withbothmaterialsthethickereithertheboardorslabis,thelongerittakestodry.

Withtimber,weknowthatdensityaffectsthedryingrate.Withconcrete,thewater-cementratiocananddoesvaryandthelowerthatthisratiois,theshorterthedryingtime.Lowerwater-cementratioconcretealsoresultsinlesspermeablehigherstrengthconcrete.Withawater-cementratioof0.5,dryingwillgenerallybeachievedwithinthreemonths.Concretewillbeslowerdryinginhigherhumiditylowertemperatureconditionsorwithhigherwater-cementratios.

Whenmeasuringthemoisturecontentofanunseasonedtimberpost,themoisturecontentsoonbecomesmuchlowerneartheexposedsurfacethaninthecore.Thesameprincipleappliestoaconcreteslab.Ifweweretomeasuretherelativehumiditythroughoutthedepthofaslabasitdrieditmayinitiallybecloseto100%.Overtime,therelativehumiditymayreduceto,forexample,50%nearthesurface,buttowardthelowersurfaceoftheslabitmaystillbewellover90%.Ineithercase,asurfacemoisturecontentreadingisnotgoingtoprovideanindicationofthemoisturehelddeeperwithinthepostortowardthebottomoftheslab.

CSorption isotherms.Source: CC&A datasheet – Moisture in Concrete


Ifatimberfloorislaiddirectlyoveraconcreteslabpriortoitdryingfromlowerdown,thenmoisturewillmigratetotheslabsurfaceandaffectthetimberfloor.Thisisillustratedinthediagrambelowfora100mmthickslaboveragroundvapourbarrier.

Fromthediagramaboveitisevidentthatsurfacemoisturemeasurementscannotbereliedontoensureperformanceofatimberflooraboveandforthisreasonin-slabrelativehumiditymeasurementisgaininginpopularityaroundtheworld.Youwillalsonoteinthisexamplethatwithflooringlaidovertheslabtherelativehumidityat40mmor40%ofthedepthoftheslabisthesameat90%relativehumiditypriortoandaftertheflooringwaslaid.Ithasbeenfoundinslabsthatdryfromonesideonly,measurementstakenat40%oftheslabdepthprovideacloseapproximationtotherelativehumiditythatwilloccurbeneaththefloorcoveringatsomelaterdate.Ifabletodryfrombothsidesthenmeasurementsat20%oftheslabdepthareapplicable.

Timber Floors and Concrete Slabs

Wheneveratimberfloorislaidoveraconcreteslabitisimportantthattheslabissufficientlydryirrespectiveofthemethodofinstallationofthetimberfloor.Asanaddedprecautionapolyethylenevapourbarrierorslabmoisturevapourbarriercanbeuseddirectlyoverthetopoftheslab.NotethatitisNOTrecommendedthatsuchbarriersbeusedtocompensateforslabswhereslabageisyoungandothertestingindicatesthatslabmoisturelevelsarehigh.Amoisturevapourbarrierwillstillpermitthetransferofsomemoistureandtherateistosomedegreedependentonthemoisturewithintheslab.Insuchinstancestheflooringcouldstillbeaffected.Notethatnotallmoisturevapourbarriersusedonconcretearerecommendedforusewithtimberfloors.Appropriatemeasuresmustalsobetakenwhenthereareconstructionjointsorwhereanewslabisaddedtoanexistingslab.

ItisimportanttoensurethatslabshavegroundmoisturebarriersbeneaththemthatcomplywithAS2870.Thesebarriersseparatetheconcretefrompossiblesourcesofmoisturethatmaydelayorcouldpreventtheconcretefromdryingadequately.Providedtheyareinstalledcorrectly,watervapourtransmissionthroughthemisminimal.Ithasbeenshownthatsuchbarriersformclosecontactwiththeslab,preventinglateralmoisturemovementbetweenthetwo.Puncturingorgapscanresultsinlocalisedareasofhighermoistureandslabedgedampnessalsoneedstobeconsidered.

Withawater-cementratioupto0.5(althoughlikelytobealittlehigherinhouseslabs)threemonthsdryingshouldbesufficientina100mmthickslabdryingfromonesurfaceonly,fora150mmthickslabsixmonthsandfora200mmthickslab12months.Ifdryingfrombothsidesoftheslabthenthesetimesarehalved.However,relyingonlyonslabageisnotsufficientasexperiencehasindicatedthatinsomeinstancesmoisture-relatedproblemshavestilloccurred.Atthetimeoffloorinstallationyouwillgenerallynotbeawareofwhattheactualwater-cementratiowas(orifwaterhadbeenaddedonsite),howwellthegroundmoisturevapourbarrierwasinstalledorhowwelltheconcretewasplaced.Thepresenceofbeamsalsoneedstobeconsidered.Asindicatedaboveaspectssuchasweather,includingtemperatureandhumidity,alsoinfluencedrying.Therefore,regardlessoftheageoftheslab,itsmoisturelevelsrequirefurtherassessmentpriortolayingatimberfloor.

Measuring Slab Moisture

Therearevariousmethodsofmeasuringthemoisturecontentofslabsandsimilartotimber,theseincludebothtypesofelectronicmoisturemeters.However,therearealsoothermeansthatmeasurethevapouremissionfromtheslab.Thesetestsincludeasimplepolyethylenefilmtest,useofahygrometertomeasurethehumidityaboveorwithinaslabanduseofvariouschemicals.

Relative humidity redistribution in a concrete slab as it dries.


Preferencesoftestmethodvaryconsiderablyandeachhasitslimitations.Metersoruseofahygrometerareoftenpreferredastheyarerelativequickandeasytouseandresultsmayberecorded.However,aswithanyelectricalinstrument,theaccuracyoftheinstrumentneedstobetakenintoconsiderationandperiodiccalibrationchecksarenecessary.Aswithalltesting,theresultsneedcorrectinterpretation.

Itisevidentfromtheabovethatwhatisimportantisthepotentialamountofmoisturethatcanbereleasedfromtheslabaswellastherateatwhichitisreleased.Testmethodsandequipmenthavebeendevelopedforeachbuteachhasitsprosandcons.

Aqualitativetestwasdevelopedwhereclearpolyethylenefilmorglassisfixedovertheslabandcondensationordarkeningoftheconcreteafter24hourscanindicateahighreleaserateofmoisturefromtheslab.However,thissimplemethodhasbeenfoundunreliableasitistemperaturedependentandresultsattimeshaveindicatedthatslabsweredrywhentheywerenot.IntheUSAthemoisturevapouremissionrate(MVER)hasbeenthestandardtestformanyyears.Calciumchloridereadilyabsorbsmoisturefromtheairandthismethodusesitsincreaseinweightwhenencasedaboveaslabtodeterminethemoisturereleasefromtheslab.Fortimberfloors15g/m2/24hrwasdeemedtobetheupperlimit.Thismethodtakesanumberofdaystocompleteandovertheyearshasbeenfounddeficientundercertainconditions.Italsodoesnotaccountformoisturedeepintheslab.InNewZealandandsomeotherpartsoftheworldarelativehumidityboxabovetheslabhasbeenused.InAustraliamoisturemeters,eitherresistanceorcapacitance,haverecentlybeenused.Asinotherpartsoftheworld,in-slabrelativehumiditymeasurementsarebeingtakenandthismethodisbecomingincreasinglyacceptedasprovidingmoreusefulinformationaboutslabmoisture.

Testmethodsandconsiderationsrelatingtomoisturemetersandin-slabrelativehumidityareoutlinedbelow.However,witheithermethoditmustberememberedthatthetestprovidesnoindicationabouthowslabmoisturemaychangeseasonallyorthatoutsidemoisturesourcescanaffecttheflooringsystem.Althoughtheflooringcontractormaynotberesponsibleforsuchexternalinfluences,itisexpectedthatthecontractorwouldassessthemoistureconditionoftheslabpriortofloorinstallation.

Withregardtothisitwouldbeappropriatetodeterminequitepreciselywhentheslabwaslaidandassessmoisturecontentsorrelativehumiditiesalongwiththeageoftheslab.Itshouldalsobeassessedwhenanolderslabmaynothaveamoisturebarrierbeneaththeslab.Thesedetailsneedtoberecordedforeachjobandfortheinstallertobesatisfiedwiththeresultspriortoproceeding.

Moisture Meters

Bothresistancemoisturemetersandcapacitancemetershavebeenavailableforsomeyears.Australianstandardssuchasthepre-2007versionofAS2455(Textilefloorcoverings–Installationpractice)specifiedthatmoisturecontentsbelow5.5%wereacceptableforresilientflooringanditappearsthatthisfigurewastakenupbythetimberflooringindustry.Inviewoftheinformationprovidedinthegraphonpage62onsorptionisotherms,itwouldappearthatthislimitisconsistentwithasaturatedslab.Therehavebeenmanyfloorslaidwithreadingsof,forexample,4.5to5%wherenoproblemswereexperienced.Inotherinstances,however,readingsofthislevelhavebeenassociatedwithfloormoistureissues.Duetothisquandaryandthefactthatmeters(particularlycapacitancemeters)onlymeasurewithin25mmoftheconcretesurface,theirusecanprovideguidanceandbeusefulforcomparativepurposesbutshouldonlybeusedaspartoftheassessment.Withonebrandofcapacitancemeter,readingsof6%to7%havebeenrecordedonaslabthatwasafewdaysoldandona5-year-oldslabwithnomoistureconcerns,readingsof1.7%to2.0%.Thisisinlinewithdatainthegraphonsorptionisotherms.


Theavailabilityofresistancemoisturemetershasreducedandthtofcapacitancemoisturemetershasincreased.Thecapacitancemeterhastheadvantageofbeingabletoperformmanytestsveryquicklyovertheslabandthereforeforthepurposeofdoingaquicksurveyandcomparingdifferentareasithassignificantbenefits.Finally,itshouldbenotedthatadditivesasusedinsomepartsofthecountrymayhaveaneffectonmeterreadings.

In-Slab Relative Humidity

IntheUSAthetestmethodiscoveredbyASTMF2170‘StandardTestMethodforDeterminingRelativeHumidityinConcreteFloorSlabsusingin-situProbes’.Simply,themethodinvolvesdrillingaholeintheslab,insertingacappedsleeve,waitingaperiodoftimeandtheninsertingaprobetomeasuretherelativehumidityoftheairintheholeintheslab.Variousspecificsofthetestingrequirementsare:

• Thein-serviceconditionsofrelativehumidityandtemperaturearetobemaintainedfor48hourspriortotesting(21°Cto29°Cand40%to60%RH).

• Thedepthoftheholeis40%oftheslabthicknessifdryingisfromonesurfaceor20%ifdryingfromtwosurfaces.

• Theholeissealedfor3daystoallowtheinternalrelativehumidityoftheairintheholestobecomethesameasthatoftheconcrete.Theprobemustbegiventimetoequilibratebeforetakingareading.

• Threetestsarerequiredforapproximately100m2offloorarea.

Therehasbeenmuchdiscussionaboutacceptablein-slabRHlevelsandnoclearguidanceisavailableatthisstage.Insomeliteratureamaximumvalueof75%issuggested,inotherliteraturespecifictoparquetryfloorsafigureof60%isquoted.However,inhumidclimatesitmaybedifficulttoachieve60%.Literatureisalsonotclearwhetherthereisadifferencebetweenabove-slabrelativehumiditylimitsandin-slabrelativehumiditylimits.Similarly,companiesproducingmeasuringequipmentdonotprovideguidanceinthisarea.

Considerations for house slab assessment

Whenconsideringhouseslabsachecklist,suchastheonebelow,canbeusedtoassesstherisk.Notethattherecanbedifferencesbetweenthereadingsofcapacitancemetersandthelimitsinthetableprovidedmaydifferandneedtobedetermined,dependingonthemeterandlocality.

Iftheanswertoanyofthefollowingquestionsis‘no’’thenrisksaregreaterandneedtobeconsidered.

1.Istheslabheight/floor>150mmabovegroundlevel(includingaboveexternalpatios)?

2.Withslabsurfacetesting,wasthe slabfoundtobesound,flatandwithnohollowsoundsunderanypatches?

3.Dowaterdropletsreadilyabsorbintotheslab?

4.Istheslabknowntobeofanagewhereanunder-slabmoisturebarrierwasabuildingrequirement?

5.Moisturetesting(refertotable)–Ifusingacapacitancemeter,recordatleast20readingsincludingallinternalandexternalcornersandwherepossibleslabthickeningsorbeamsmaybepresent.Areallreadingsinthemoderatetolowrangeofthetable?Ifusinganin-slabHygrometerarethereadingsbelow75%?


Appendix D – Acoustic Performance

Timberfloorsareusedinmanymulti-storeyapartments,bothinnewconstructionandrenovationwork.Withnewprojects,buildingregulationsoftenapplyrestrictionstosoundtransmissionbetweenunitsandinrenovationworkthenoiseassociatedwithanyreplacementfloorcanoftenbenogreaterthantheoriginalfloor.Withregardtosoundtransmission,timberflooringissimilartootherhardflooringsurfacesand,inparticular,itwillfreelytransferimpactsounds.Forthisreason,itisnecessarytoensurecorrectdetailingandinstallationmeasuresinordertoprovideafloorsystemwiththerequiredsoundperformance.

Noise Transmission Through Timber Floors

Whenevertheacousticperformanceofamaterialisbeingtestedgreatcareistakentoensurethematerialisisolatedsothatonlythesoundtransmissionthroughthatmaterialisbeingtested.Whenmaterialsarenotisolated,asoccursinbuilding,thatisfloorsconnectedtowallsandwallsbeingcommontoupperandlowerstoreyunits,additionalnon-directsoundtransmissionpathsor‘flanking’pathsareintroduced.Soundfromafloorabovecanthenradiatefromthewallsurfacesintheunitbeneathandthiscancontributeconsiderablytosoundtransmissionbetweenunits.

Thisindicatesthatgreatcareisnecessaryinbuildingdesignanddetailingtoprovideeffectivesolutionsandthesystemneedstoconsiderprovidingisolation,absorptivematerialsandincreasedmass(i.e.slabthickness).Eachoftheseisimportantinordertoreducesoundtransmission.Timberfloors,aswithotherhardfloorsurfaces,areparticularlyaffectedbyimpactnoiseresultingfromfoottraffic.

Acoustic underlay and fl oor isolation signifi cantly reduces direct and fl anking noise transmission.

Approaches to Improve Acoustic Performance

Timber fl oors on battens

Timberfloorsoverconcreteslabsareoftenfixedtobattenswhichare,inturn,directlyfixedtotheconcreteslab.Toprovideadegreeofisolationbetweentheslabandthebatten,resilientpadsmaybeusedbetweenthebattenandtheslab.Fixingofthebattentotheslabisstillnecessaryandthiswillresultinsomesoundtransmission.Generally,thickerbattensrequirelessfrequentfixingandtherebyreducethefrequencyofdirectfixing.Withbattensat450mmcentres,19mmstripflooringmaybeusedfordomesticloading.Theflooringmaybesecretlyfixedto19mmthickhardwoodsbattenortop(face)nailed.Iftop(face)nailingisusedthehardwoodbattensneedtobeatleast35mmthick.FormorespecificdetailsoffloorfixingrefertoSection3ofthismanual.

D


Timber floors over sheet floors

Thissystemutilisesacompletesheetofacousticunderlayoveranexistingtimberfloororslab.Aplywoodsub-flooristhenlaidovertheacousticunderlayandfixedtotheslabortimberfloorbeneath.Again,thefixingofthesub-floorwillresultinsomesoundtransmission.Both19mmthickandoverlayflooringmaybeusedinthisinstanceastheboardsarefullysupported.Secretfixingwiththeadditionofapolyurethaneflooringadhesiveisgenerallyusedtofixtheboards.MorespecificfloorfixingdetailsareprovidedinSection3ofthismanual.

Other Important Considerations

Selecting the underlay and isolation pads

Thepurposeoftheunderlayorpadsistoprovideisolationofthetimberfloorfromthebuildingelementsbeneath.Manyproductsareavailableandeachshouldhavetestdatarelatingtoperformance.

• Padsneedtobesufficientlythicktoensureseparationismaintainedwhenthefloorisbeingwalkedon.

• Theproductneedstoberigidtopreventcompressionwhentheflooriswalkedon.

• Itneedstoprovidelong-termperformancewithoutflattening,particularlyunderheavyappliancesandfurniture.

Isolation at floor edges

Itwasoutlinedabovethatisolationisakeyaspecttopreventflankingsoundtransmission.Gapsneedtobemaintainedbetweentheflooringandallwalls,steps,windowjoinery,etc,andasmallgapisalsonecessarybetweentheskirtingandthefloorboards.

Further improvements

Improvementsinsoundstransmissionfromafloortoaunitbelowcanalsobeachievedatthedesignstagebyensuringthattheslabisofadequatethickness.Anextra25mminslabthicknesscanmakeasignificantdifferencetosoundtransmission.Inadditiontothis,ceilingsystemscanalsobeusedwhichisolatethesoundsource(i.e.timberfloor)fromtheunitbeneath.Thesesystemsgenerallyconsistofagridofisolationmountswithfurringchannelsattached.Insulationandplasterboardcompletethesystem.Withmulti-residentialtimberframedconstruction(MRTFC)twolayersoffire-ratedplasterboardareused.Suchsystemsareeffectiveandareconsideredtoberelativelyeconomical.Finally,rugs,hallrunnersandmatsusedinconjunctionwithtimberflooringcannotonlycomplementthetimberfloorbut,withtheirsoundabsorbingproperties,canalsoreducenoiselevelsbothwithinandbetweenunits.


Appendix E – Underfloor HeatingTimber Floors and Underfloor Heating

Timberfloorswithunderfloorheatingsystems(UFH)arecommoninEuropeandNorthAmerica.InthecoolersouthernstatesofAustraliatheyarenotcommon,yetpublicinterestisincreasing.Duetothelimitednumberofinstallations,experienceinAustraliaislimited,particularlywiththemediumandhigherdensityhardwoodsthatareavailable.ResearchbytheCentreforSustainableArchitecturewithWood(UniversityofTasmania)hasrecentlyevaluatedtheuseofoverseaspracticeswiththeperformanceofMessmateandBlackbutt.FloorswithanunderfloorheatingsysteminplaceweremonitoredinTasmaniaoveraperiodoftime,throughwinterandsummer.ThisappendixprovidesguidanceregardingtheinstallationoftimberfloorsoverunderfloorheatingsystemsandisrelevanttothesouthernstatesofAustralia.

The Climate Experienced with Heating Systems

Temperatureandrelativehumidityarethetwokeyfactorsthatinfluencetheinternalclimateorenvironmentwithinadwelling.Anincreaseinthetemperatureinsidethedwellingwillcausealoweringoftherelativehumidityandwiththisthedryingcapacityoftheairincreases.Lowrelativehumiditywillresultintimberflooringreleasingsomeofitsmoisturetotheair,andtherebyreduceinmoisturecontentandshrink.Themoisturecontentofafloorisaffectedbychangesintheheatedenvironment.Thetermequilibriummoisturecontent(EMC)isoftenused.EMCcanbethoughtofasthemoisturecontentthattimberwillattainundersetconditionsofrelativehumidityandtemperature.Iftheconditionsinsideadwellingaremaintainedat20°Cand60%RHthentheflooring,dependingonitscurrentmoisturecontent,willeithertakeuporlosemoisturetotrytoattainamoisturecontentofabout11%.

TheexternalEMCcanbecalculatedfromweatherdataandthegraphbelowillustrateshowthisvariesseasonallyforthesouthernstates.TheexternalRHduringwinterishighandinsummeritismuchlower.Whencoolerexternalairisthenheated,asinaninternalenvironment,theRHandthereforetheEMCdropssignificantly.TheTasmanianstudycalculatedtheeffectofEMCvaluesresultingfromheatingto20°CfortheperiodfromMaytoSeptemberandthisisshowninthelowergraph.

E

Source: FWPA Project PN07.104 – Advanced Research into Floor Performance Issues – University of Tasmania – 2008.


AscanbeseenfromtheprecedinggraphstheeffectisdramaticandsuggeststhattheconditionsassociatedwithaheatedinternalenvironmentwillresultinEMCsbetween8%and9%duringtheheatingperiod.Notethatbothgraphsarebasedonexternalrelativehumidityvaluesandalessextremevariationwouldbeexpectedinsideadwelling.Evenso,theflooringneedstobeabletocopewithverydryconditionsduringtheheatingperiodoverwinterandmoderaterisesinmoisturecontentoversummer.Whilethiscanbecateredfor,thereisanobviousconcerniftheUFHsystemwasnottooperateforasignificantperiodoverwinterasthiscouldcreateexpansionthatwasgreaterthanwouldoccuroverthesummermonths.

Choice of Timber Flooring

IntheTasmanianresearchundertakentwospecieswerechosen,Messmate,amediumdensityhardwood,andBlackbutt,ahigherdensityhardwood.Bothspeciesareknowntoberelativelyresponsivetomoistureuptakeandlossfromtheair,however,underfloorexpansiontheBlackbuttwouldtendtocrushlessatboardedgesandresultingreaterexpansionforces.BlackbuttisalsousuallybacksawnwhereasMessmateisusuallyquartersawn.Forthesameincreaseinmoisturecontentabacksawnboardwillswellmorethanaquartersawnboard.Thecoverwidthofthe19mmthickflooringusedintheresearchwas85mmforTasmanianOakand80mmforBlackbutt.

IntheUnitedKingdomrecommendationsaretolimitboardwidthto75mmwithunderfloorheatedapplications,however,withAmericanOak,acoverwidthupto130mmhasbeenfoundtogivegoodresults.ItisnotrecommendedthatboardwidthsinAustraliaexceed130mmandthepreferenceisfor80mmor85mmboardsintheseapplicationstominimisegappingandthepotentialforacuppedorcrownedappearance.

TheTasmanianresearchindicatedthat19mmthickflooringwasconsiderablymorerobusttoeffectsofcuppingthan12mmthickoverlaymaterial.Itmustbeconsideredthatintimeswhenheatingmaynotbeonandfloorexpansionoccurs,thenthethinnerboardswillbemorereactiveandtheriskofcuppingisveryhigh.Forthisreasonaboardthicknessof19mmisrecommended.

Concerningthemoisturecontentoftheflooring,AS2796indicatesanormalmanufacturingrangeof9%to14%.However,researchhasindicatedthat8%to9%,whichisnearthemiddleoftheexpectedinternalseasonalrangeinAustralia’ssouthernstates,ismoreappropriate.Overseas,anaverageof8%isoftenrecommended.InAustraliaitisunlikelythatmanufacturerswillproducespecificbatchesofflooringattheselowmoisturecontents.Muchoftheflooringisproducedtothelowerendofthe9%to14%rangeofAS2796andflooringpackswithboardsaveraging10%arelikelytobeavailable.Toobtainthis,closeliaisonbetweenmanufacturerorsupplierandtheinstallerwouldbenecessary.Todeterminesuitability,theproposedflooringwouldneedtobesampledandovendrytestingundertakentodetermineexactmoisturecontents.Thiscanbeexpectedtoaddsomecostbutisconsideredimportant.Also,greatcareofthelowermoisturecontentflooringneedstobetakentoensureminimalchangeinmoisturecontentpriortolaying.Irrespective,somegappingatboardedgesafterinstallationcanbeexpectedasaresultoftheunderfloorheating.

Heating System Considerations

Heatingsystemsusedwithsolidtimberfloorsrangefromhydronicheating,wherewarmwaterispipedthroughaconcreteslabbeneaththefloor,toelectricheatingsystemsbeneaththefloor.Itisnecessarythattheclientmakesavailabletothefloorinstallerfullinstallationandoperatinginstructionsofthesystemthatisinplace,andthatthesystemorproposedsystemisconsideredcompatiblewithsolidtimberfloorsbytheheatingsystemmanufacturer.

Evenheatdistributionisvitallyimportantashotspotscancausegreaterboardmovement(shrinkageorcupping)insomeareasofthefloorcomparedtoothers.Pipeswithinaslabsetatdifferentheightscanbethecauseofthisandtheinstallershouldmaketheclientawareofthispossibility.

Sydney Blue Gum floor with underfloor hydronic heating.


Theclientshouldalsorecognisethatwithseasonaloperationofthesystemsomegappingandchangeinboardshape(slightcuppedorcrownedappearance)islikelyandparticularlysoiftheclienthaschosenwiderboards.

Theclientalsoneedstobemadeawareoftheconstraintstothesystemwithregardtooperatingtemperatureandtheneedtoavoidabruptchangeswhenadjustingfloortemperature.Smallincrementsof2°Cperdayareappropriateandunderfloortemperaturesshouldnotexceed27°C.

Typical Installation Procedures

Installationproceduresincountriesthatmoreregularlylayfloorsoverunderfloorheatingarerelativelyconsistentbutcanvaryincertaindetails.

Atypicalprocedure,providedforguidanceonlyasAustralianexperienceislimited,involvesthefollowingsteps:

1. Site conditions

Thesiteshouldbefreefromallwettrades,beinastatewherethedwellingcanbelivedinandwiththeheatingsystemfullycommissioned.Thesub-floorshouldalsohavebeenlevelledifnecessarytoacceptthetimberfloor.

2. Pre-heat the sub-floor prior to laying to remove excess sub-floor moisture

Theheatingsystemneedstobeoperatedfor2weekspriortofloorinstallationtolowerthemoisturecontentofthesub-floorandparticularlysoifitisaslabtoremovefurthermoisture.Thepossibilityofhigherlevelsofhumidityintheroomduringthisprocessshouldbecheckedforandventilationprovidedasrequired.Whenconditionsaresufficientlydry,theflooringshouldbestoredintheinstallationlocationinamannerthatdoesnotinterferewiththedryingofthesub-floor.Duringandparticularlytowardtheendofthisperiodtheroomconditionsregardingtemperatureandhumidityshouldbecheckedandtherelativehumidityshouldbeintherangefrom45%to60%atatemperatureofabout20°C.ThisequatestoanEMCof8.5%to11%.Themoisturecontentoftheflooringtobelaidshouldhavealreadybeenthoroughlycheckedpriortosupplytoensurethatboardsaregenerally9%to10%moisturecontentandthisshouldagainbecheckedpriortolaying.Similarly,thesub-floorshouldalsobecheckedtoensureitissuitableforacceptingatimberfloor.Thesub-floortemperatureshouldnotexceed27°Cwithin-slabheating.(Withhydronicheatingwatertemperaturesmaybe45°Corsotoattainanunderfloortemperatureupto27°C.)

3. Turn off the heating and follow this by a non-heating period

Theperiodoftimethattheheatingremainsoffisgenerallyabouttwodays.

4. Lay and fix the floor

Ifthefloorislaiddirecttoaslabthenanelastomericpolyurethaneadhesiveisused,andasthismaydifferfromthoseusedwithnormalfloorinstallation,adviceshouldbeobtainedfromtheadhesivesupplier.Forothertypesofsub-floor,normalfixingpracticesapply.Followinginstallationtheheatingistoremainoffforafurthertwodays.

Blackbutt flooring (130 mm wide) with electric underfloor heating in Adelaide.


5. Gradually increase the UFH to normal expected temperature

Theheatingshouldbeincreasedinstagesfromalowleveltothedesiredroomtemperatureoveraperiodofabout10days,incrementingbynomorethan2°Ceachday,andthenmaintainedforafurthertwoweeks.

6. Sanding and finishing

Recommendationsvarywithsomeindicatingthatitshouldbecarriedoutabout3daysaftertheheatingwasturnedbackon,whileothersindicatethattheheatingshouldbeturnedoffandthefloorsandedtwodaysafterthefloorhascooled.

7. Turn the heating system on

Thesystemwithinstalledandfinishedfloorcanthenbeoperatedbutagainthetemperatureshouldberaisedgraduallytothedesiredoperatingtemperature.WithanUFHsysteminplacetheoptimumrelativehumidityrangeisbetween45%and60%yearroundwithroomtemperaturesofabout18°Cto24°C.


FAppendix F – Installation Checklist

Assessing Packs of Timber Flooring

FlooringManufacturer:

PackNos:

Species/Speciesmix: Coverwidth: Grade:

Wrappingisingoodconditionandtherearenosignsoftheproductgettingwet.Yes No

Boardsshouldbecheckedfor:

•Cupping (Useasteelruleorsimilar)

•Cover width variation(Shouldnotvarybymorethan1mmbetweenboards)

•Tongue and groove tolerance (Snugfittoslightlyloose)

Note: Cover width variation exceeding 1 mm, sloppy T&G fit, signs of moisture or cupping may indicate possible problems.

Records

Widest Moisture Cover Cupping Narrowest Moisture Cover Cupping Boards Content Width Boards Content Width

1 1

2 2

3 3

Note: Ensure that the appropriate moisture meter corrections have been applied. Moisture contents should be between 9% and 14% (average between 10% and 12% is common).

Site Conditions and Installation Environment

Sitelocation:

Average9amRH: AverageextEMC:

Note: If the external EMC is greater than 2% higher or 1% lower than the estimated average moisture content then additional provision for future expansion or shrinkage needs to be considered (see Section 2).

Ifapplicable,aresub-floorconditionsdry,groundlevelsbeneathdwellingnotlowerthanexternalgroundandgradedtopreventponding,ventilationtorecommendationsandgroundslopingawayfromdwelling?

YesNo

Note:If‘no’thentheseissuesmayneedtobeattendedtoorothermeasurestakenpriortoinstallingthefloor.


Ifthefloorislaidonjoistsensurethejoistsaresufficientlylevel.

Ifthefloorisoveraconcreteslaborsheetsub-floor,arethesub-floorsadequatelylevel,dryandingoodcondition?

YesNo

Slabmoisturecontentsorchecksundertakenwiththefollowingresults:

Slablevelcheckedandwithin±mmin1.5mthroughout(plywoodorbattensystem).

Note: Maximum is ± 3 mmIfsheetsub-floorshavebecomewetpriortoorduringconstructionandmaynothavesufficientlydriedthenmoisturecontentsneedtobechecked.Moisturecontentsareasfollows:

Note: Plywood and particleboard moisture contents need to be determined with oven dry testing. Sheet sub-floors should be within 2% of the timber flooring moisture content being laid over it. Slab moisture assessed in accordance with Appendix C.

Ifthefloorisoveraconcreteslabthencheckitforconstructionjointsanddeterminewhetherithasamoisturebarrierbeneaththeslab.

Note: If construction or similar joints are present in slabs then possible moisture penetration from capillary action needs to be considered. Older slabs may not have moisture barriers beneath the slab and are more prone to seasonal moisture fluctuations that can affect timber floors.

Thefollowingslabmoisturebarrierasapplicablehasbeenappliedtoorovertheslab:

Expected Movement After Installation

Ifwideboardflooringisbeingusedgreatershrinkagecanbeexpectedduringdrytimes.

Inmoistlocalitieshighlevelsofexpansioncanbeexpected(ensureadequateadditionalexpansionallowance).

Isthebuildingdesignsuchthatthefloorwillexperiencehighlevelsofsunlightorhasheating/air-conditioningsystems?(Drierin-serviceconditionscanbeexpectedatcertaintimesoftheyear–shrinkagegapsmorelikely.)Istheundersideofthefloorexposedtodrywindsormist?(Sealingorprotectiontotheundersideofthefloorneedstobeconsideredtoassistincontrollingbothexpansionandshrinkage.)Istheflooranupper-storeyfloor(drierin-serviceconditionscanbeexpected–shrinkagegapsmorelikely)orbelowgradeinshadyconditions?(Moisterin-serviceconditionscanbeexpected–ensureadequateexpansionallowance–referSection2.)


Installation Moisture Content and Acclimatisation

Basedontheexpectedin-servicemovementthefollowingpre-installationprocedureshavebeenundertaken:

Note: Acclimatisation (flooring stripped out or loose laid) or provision of additional expansion allowance, etc, should be recorded.

Method of Installation

Thisfloorisbeinglaidbythefollowingmethod:

Choice of Finish System

Basedonthemovementexpectedandconditionoftheflooratthetimeofsandingandfinishingsomefloorfinishesaremoreappropriatethanothers.(Possibleissuessuchaswear,grainraise,edge-bondingandwhitelinesneedtobeconsidered.)

Thefinishsystemusedonthisflooris:

Note: The above is provided as a guide only. Additional testing may be necessary or there may be the need for other considerations.


Appendix G – Troubleshooting Guide

Performance of Timber Floors

Inmostinstancestimberfloorsperformwellinawiderangeoflocalitiesandwithawiderangeofinstallationpracticesdependingonthesub-floortype.Therecan,however,beinstanceswheretheperformanceorappearanceofthefloorcanbeaffectedandthemajorcontributingfactorsare:

•ThemanufactureoftheproductdoesnotmeetAustralianStandards.•Recognisedinstallationandfinishingproceduresarenotfollowed.•Moistureingressdirectly(e.g.leaks)orindirectly(e.g.seepageintosub-floorspace).•Aspectswheretheownerhasnotpaidadequateattentiontothefloor.

Thetablebelowoutlinessomeoftheperformanceissueswithtimberfloors,commoncausesandhowtheyappearinthefloor.

Performance Issue

Common causes Appearance in the floor

Cupping •Moisturefrombeneaththefloor.•Dryconditionsabovethefloor.•Highmoisturecontentsinboards

attimeofmanufacture.

•Boardscupthroughoutthefloorandtheflooristight.

•Boardscupthroughoutbutgapsarepresentatboardjoints.

•Someboardsinthefloorwillcupinthefloorbutnotothers.

Crowning •Moistureuptakeandthefloorsandedandfinishedinthiscondition.

•Duringdryperiodsthefloorgapsatboardedgesanddevelopsawashboardlook.

Peaking • Highpressureontheuppershoulderoftheboardoftenresultingfromatmosphericmoistureuptake.BoardtolerancesandMCdifferencesbetweensupplyandin-servicealsocontribute.

•Thejointsatboardedgesareraised.Thiscanhavetheappearanceofcupping.

Tenting • Highexpansion.Maybedirectlyrelatedtohighhumidityorothermoistureissues.Mayrelatetoinadequateexpansionallowance,poorventilationorinadequatefixing.

•Adjacentboardsinthefloorriseatthejointabovethelevelofthefloor.

Buckling • Highexpansion.Maybedirectlyrelatedtohighhumidityorothermoistureissues.Mayrelatetoinadequateexpansionallowance,poorventilationorinadequatefixing.

•Agroupofadjacentboardsliftoffthesub-floor.

Wide or irregular gapping

• Thefinishgluingadjacentboardsandthefloorshrinking.

• Highmoisturecontentsinboardsattimeofmanufacture.

• Boardsinappropriatelystoredandhavetakenupmoisturepriortolaying.

• Wideboardsanddryconditions.

•Loudcrackingnoises,irregularlyspacedwidegapsandsplitsthroughboards.

•Gapsatboardedgesassociatedwithnarrowcoverwidthboards.

•Frequentgappingandthemeasurementoversectionsofthefloorisinconsistent.

•Regularwidegaps.

G


Sanding and Finishing Imperfections

Ahighstandardofsandingandfinishingcanbeexpected,howeversomeimperfectionscanbeexpected.Thedegreetowhichimperfectionsareapparentdependsonmanyfactorsincludingtimbercolouranduseofdownlights,bothofwhichcanhighlightsuchthingsassandingmarksanddustinthefinish.Consequently,itisdifficulttoprovideobjectivemeasuresoffinishingimperfections.Evenso,itisknownthatahighstandardofworkmanshipalsoprovidesanequallyhighstandardofcustomeracceptanceandsatisfaction.Whentheappearanceofafloorisbeingassessed,theassessmentshouldbecarriedoutindaylighthourswithlightsonandcurtainsorblindsintheirusualposition.Imperfectionsshouldbeviewedfromastandingpositionafewmetresawayandfromvariousdirections.Iftheimperfectionisdifficulttodiscernthentheappearanceisgenerallysatisfactory.Itshouldbenotedthatviewinganyimperfectiondirectlytowardlightsources,suchastowarduncoveredslidingexternaldoors,willalwaysexaggerateimperfectionsandthisneedstobeconsideredwhenevaluatingthefloor’sappearance.Inadditiontothis,aspectstobeconsideredshouldincludewhethertheimperfectionisinexcessofwhatwouldgenerallyoccur,whetheritislikelytobecoveredbyfurnitureorfloorrugsandwhethertheimperfectionwilldecreaseintimewithfoottraffic.Thetableoppositeoutlinessomeofthesandingandfinishingimperfectionswithtimberfloors,commoncausesandhowtheyappearinthefloor.

Tenting resulting from atmospheric moisture uptake.

Rejection and contamination in the finish.

Wide gaps due to high moisture contents at the time of machining.


Appearance Issue

Common causes Appearance in the floor

Rejection • Contaminantsleachingoutoftheflooringaffectingthecuringofthefinish.

•Rangesfromachangeinalocalisedglossleveltoan‘orangepeel’appearance.

Delamination • Movementofthetimberatboardjointsorattheendoftheboard.Inappropriatesealers.

•Thefinishpeelsatboardjointsorboardend.

Quilting • Surfacecoatingsflowintothejointsbetweenboards.

•Alackofconsistencyofthecoatingoverboardjointshighlightingthejointsandgivingabedquiltappearance.

Contaminants • Floornotclean.• Windyexternalconditions.• Dustingappedboardsorunder

skirting.

•Smallspecksorinsectsinthefinishwhichisoftenworsenearpoorlysealingexternaldoors.

Ghosting • Peoplewalkingontheflooratthetimeofsandingandfinishingwithcertaintypesofbootsandfootwearorbarefeet.

•Afteraperiodof12monthstotwoyearstheappearanceofafootorbootprintappearsinthefloorasalightercolour.

Pimples • Fineairbubblesoccurringduringcoatingapplication.

•Poppedbubblesinthefinish.

White lining • Therapidstretchingofwaterbornefinisheswhenboardsgap.

•Whitelinesappearingalongboardjoints.

Edge bonding • Finishflowingintogapsatboardedgesandgluingboardstogether.

• Thinnedfinishusedasasealerandpenetratingfinejointsbetweenboards.

•Wideirregularspacedgappingatboardedges.

•Splitsinboards.

Gloss variation • Weatherconditions.• Surfaceevennessoftheboards.

•Shinyanddullpatchesinthefinish.

Swirl marks • Rotarysandingparticularlyattheedgesoffloors.

•Circularswirlingscratchmarks.

Chatter marks • Vibrationinthefloor.• Sandingtechnique.

•Undulationsrunningacrossseveralboards.

ForfurtherinformationonthefloorinspectionprocessandmanyofthemorecommonproblemsrefertotheATFAPublication‘Problems,CuresandRemedialMeasures’.

T 1300 36 1693 E [email protected] W www.atfa.com.au

Publications available • Consumer Guide to Timber Flooring • Timber Flooring Manual • Problems, Causes and Remedial

Measures Manual• Information Guides and Data Sheets

– Owner expectations for completed timber oors

– Timber colour and grade– Coating choices– VOC Guides for coatings and adhesives– Care and maintenance – Plus many more.

Services available • Floor inspection service • Technical advice• Workshops and training schools• Timber Flooring Convention • Customised training.

Membership• ATFA membership is available for businesses

in the timber ooring industry, providing a toolbox of support, information and savings.

Visit www.atfa.com.au for more information on services, products and membership options.

The Australian Timber Flooring Association is the peak industry body for timber flooring in Australia. ATFA provides information and support to specifiers, installers, finishers and consumers of timber flooring.

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