cl/sfb (13.9) ln6 a comprehensive technical guide technical guide.pdf · water vapour pressure ......

technicalguide

a comprehensive

to the specification of

vapour controllayers

technicalguide

a comprehensive

to the specification of

vapour control layers

Cl/SfB (13.9) Ln6

..the knowledge to produce solutions

G R O U P L T D www.proctorgroup.com

A Proctor Group

two

Partnerships in action•••••••••••••••••••••THE PROBLEM

Moisture in today’s buildings can be a continuousproblem if not tackled professionally. Equally, newand existing buildings, particularly those that willhouse hi-tech machinery and computer equipment,need to be guarded against condensation and itsconsequences.

Homes fitted with double glazing no longer havenatural outlets for moisture; while industry demandsa higher level of comfort for its workers.

The loft conversion market, too, seeks faster, moreeffective production methods that will bringconfidence in guarantees.

THE SOLUTION

The A.Proctor Group, with its history of successfultechnical solutions, recognised these problems andhas linked with two manufacturers to offer totalsolutions to all the traditional problems of vapourcontrol.

All the manufacturers use state of the art plant andproduction equipment, and operate withinrecognised quality standards.

These total solution products offer the mostcomprehensive range available. Each one is fullyresearched and tested to ensure completesatisfaction and guaranteed performance.

THE KNOWLEDGE

The A.Proctor Group has, for over 40 years, beenserving the construction industry with an extensiveportfolio of technically advanced thermal, acousticand membrane products.

This commitment to develop a complete membranerange, covering Vapour Control Layers and BreatherMembranes in pitched roofing and industrialcladding, has resulted in a unique, exclusivepartnership with two of the U.K’s largest and mostrespected membrane manufacturers.

BSk, based in Strood, Kent, manufacture the U.K’sonly reinforced polyethylene and polyethylene /foilVapour Control Layers to a carefully determinedspecification. ISO 9000 quality procedures ensureproduct reliability and performance.

Don and Low Nonwovens have now addedRoofshield, for domestic pitched roofing, toCladshield and Frameshield, the U.K’s top brandsin the industrial cladding and timber frame markets.

A nationwide technical specification team, togetherwith Tecline Advice Centre, ensure professionalresponse to the industry’s requirements. A nationalnetwork of distribution outlets ensure prompt andeffective service.

(below)A. Proctor Group’sHead Office-The Haugh,Blairgowrie, Perthshire.

G R O U P L T DG R O U P L T D

A Proctor Group

The Importance of Vapour Control

Product Selector

Membrane Information Sheets

Details and Installation

Preferred Details

page 4-9

page 10

page 11-12

page 13-14

page 15

three

OBJECTIVE OF TECHNICAL GUIDE

This Technical Guide offers good advice on the specification and installation of membranes to controlwater vapour within roof and wall constructions. By adopting the practical measures given in this TechnicalGuide, the design and build team can reduce the risks of condensation, water ingress and excessive heatloss after the building has been completed.

Contents••••••••••••••••••••••••••••••

A Proctor Group

four

INTRODUCTION

It has been long recognised that condensationwithin buildings can be a problem. But how can itbe minimised? The starting point is to look at thesources of moisture within a building.

SOURCES OF MOISTUREWITHIN A BUILDING

Domestic Functions

Cooking, washing and drying clothes, dish washing,bathing and showering are all everyday activitiesthat result in the internal air coming into contactwith water and turning to steam or “vapour”.

People

Our bodies perspire, especially when we areexercising. It has been estimated that a persontypically generates 1.2 litres of moisture per day.This becomes much more of an issue when largegroups of people are gathered together, such asin a school, a theatre or a sports hall.

The Importance of Vapour Control••••••••••Industrial Processes

Many industrial processes will involve vapourgeneration for example textile and paper mills,laundries, printing houses. Indoor heated swimmingpools and leisure pools will also create moisturewhich requires control.

Construction

Wet finishes such as concrete slabs, screeds, masonryand plaster are installed with a lot of water withinthem. For example, a 150mm thick concrete slabwould have approximately 27 litres within eachsquare metre when first cast and drying out takesmany months, often long after the roofing andwalling have enclosed the slab.

WATER VAPOUR PRESSURE

Internal conditions within a building are measuredin terms of:

• air temperature in oC• relative humidity in %

Using the “psychometric chart” the vapour pressurein kiloPascal can be read off.

The greater the vapour pressure within thebuilding, the greater the condensation risk.

The notional indoor conditions for a range of buildingtypes are given in the table and are plotted on thechart. Higher humidities are generated in kitchens,bathrooms and laundries.

With the information about what is likely to begoing on in the building, the designer is in a positionto take the design forward.

(below)British American Tobacco,Southampton.

G R O U P L T D

CONDENSATION

The air around us holds moisture in the form of acolourless vapour; the warmer the air, the greaterthe amount of moisture it can hold. If the air is cooled,then it cannot hold as much moisture and therecomes a point at which the water changes from avapour to a liquid, which we see in the form of“condensate”. At this point the “relative humidity”is 100%.

As an example, we can see this when we take a coldbottle of wine out of the fridge. The air containingwater vapour is cooled as it passes over the glassbottle, such that the air can no longer hold the watervapour and a film of water droplets forms ascondensate on the bottle. Another everyday exampleof condensation is on a mirror in a bathroom. As wehave a bath or shower, vapour is released into theair, thus the humidity levels increase. As the vapourladen air passes the mirror the temperature dropsand the vapour is released on the mirror in the formof water.

Condensation occurs within roof and wallconstructions if the heated internal air escapes throughthe lining and insulation then comes into contact withthe cold outer surfaces, forming condensationwhich can drip back down into the building.Alternatively with a metal roof on a cold clear nightthe surface temperature of the metal sheets maybe significantly less than the surroundingambient temperature. Significant quantitiesof ice and/or condensation may formon the underside of the weather sheet.Such effects are caused by nightradiation and wind chill.

A Proctor Group

f ive

The Importance of Vapour Control••••••••••

Type of building Dry Bulb Air Relative VapourTemperature oC Humidity % Pressure kPa

A Factories andheated warehouses 15 35 0.6

B Offices 20 40 0.9

C Schools 20 50 1.2

D Houses and flats 20 55 1.3

E Textile factories 20 70 1.6

F Swimming pool halls 25 70 2.2

Moi

stur

e co

nten

tg/

kg d

ry a

ir

Vap

our p

ress

ure

KPa

-5 0 5 10 15 20 25

20

19

18

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

3.2

3.0

2.8

2.6

2.4

2.2

2.0

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

3.1

2.9

2.7

2.5

2.3

2.1

1.9

1.7

1.5

1.3

1.1

0.9

0.7

0.5

0.3

0.1

80604020

9070503010

Rela

tive

Hum

idity

%

Saturation

Wet bulbtemperature °C

Dry bulbtemperature °C

Table 1 - Notional internal conditions, taken from BS6229

HIGH

MODERATE

LOW

The threshold between the‘high/moderate’ internal vapourpressure is taken as 20°C 60%RH(=1.4KPa).The threshold between the‘moderate/low’ internal vapourpressure is taken ashalf of the upper threshold(=0.7KPa).

A Proctor Group

six

AFFECTS ON BUILDING FABRIC

Condensation within roof and wall constructionscan lead to serious problems:

• Timber can rot, causing severe structural weakening reducing life of structure.

• Wetting can cause timber and otherhygroscopic materials to swell, resulting in distortion and permanent damage to sarking boards and wall plates.

• Corrosion may occur on unprotected metal surfaces, including components such as rooftruss nailplates.

• Insulation materials may absorb moisture and lose their thermal effectiveness.

• Ceilings and decorations can be damaged by condensation soaking through.

• Mould growth can form, presenting ahealth hazard.

• Condensation may effect electrical wiring withinthe hidden roof and wall spaces.

• Items such as furniture stored in a loft space can be permanently damaged.

The Importance of Vapour Control••••••••••With the continuing trend to increase the thicknessof thermal insulation, the risk of unwantedcondensation forming will be ever present andhence the need for care in dealing with vapourcontrol in buildings. Solving condensation problemsafter a building is completed is not straightforward,and sometimes requires the total dismantling of theroof or wall, which is a costly repair.

TACKLING CONDENSATION

Reduce the internal vapour pressure.

Where possible remove the source of moisturewithin the building. Improve the internal ventilationand airflow, such as by opening windows andproviding ventilation.

Provide a continuous barrier to stopvapour entering the roof or wall.

The vapour control layer needs to be continuousand impose a substantially greater vapour resistancethan the total of the elements above, i.e. theinsulation / breather membrane / roofing or walling.A continuous vapour control layer will have theadded benefit of reducing the amount of heatedair escaping from a building. By stopping these“draughts” and reducing air convection losses thethermal performance of a building can besignificantly improved.

Promote the release of moistureabove the vapour control layer

Any vapour that does get past the vapour controllayer needs to have a path out of the building witheffective ventilation. Therefore minimise theexternal vapour resistance and allow the externalskin to breathe. (See illustration left)

1 Warm Vapour laden air

2 Dispersed Vapour

3 Decking

4 Vapour Barrier

5 Insulation

6 Breather Membrane

7 Vapour Condensate buildsup on underside of roof, water droplets fall onto waterproof breather membrane and run offinto gutter.

8 Outer Covering

9 Cold Air

6 78

9

43

1

2

5

Insulation values can be effectedby the build up of condensation

G R O U P L T D

A Proctor Group

seven

The Importance of Vapour Control••••••••••MEASURES TO IMPROVETHE EFFECTIVENESS OF AVAPOUR CONTROL LAYER

1. Respect the vapour control layer

Through all stages of the construction sequence ahigh standard of care and attention must be given,from the original specification, detailing stages,storage of materials on site through to installationand final inspection. All members of the designand construction team should be fully aware thata roof with an ineffective vapour control layer canonly be repaired properly by stripping the entireroof and starting again or by over-roofing.

2. Select a vapour control layer withhigh vapour resistance

Industry guidance suggests that the vapourresistance of a vapour control layer within high riskroofs should be at least 500 MNs/g.The addition of an aluminium foil greatly enhancesthe vapour resistance.

3. Select a vapour control layer withgood tear resistance - The importanceof multifilament reinforcement.

The vapour control layer is often subjected toreversals of wind pressure, causing the membraneto ‘drum’ against supports. If there is room formovement and there are sharp edges, then themembrane can tear. It has been found thatmonofilament reinforced vapour control layersoften have small pockets of air entrapped eitherside of their relatively bulky reinforcement, whichreduces the tear resistance.

Monofilament

Multifilament

4. Provide good support

On cold roof constructions where the vapour controllayer is draped between purlins, the laps are extremelydifficult to seal. This arrangement is best avoidedand must not be used in high risk areas. Instead arigid safe lining sheet should be provided for laying,jointing and sealing the vapour control layer.

For advice on high risk areas please contact APGTechdesk.

Warm roof constructions have the benefit of astructural deck directly below and offering goodsupport. Rigid structural decks and safe walkablelining sheets are recommended to give full supportfor laying and sealing the vapour control layers. Thisis one of the reasons why the BRE recommends awarm deck roof above swimming pools. Overtrapezoidal decking, the side laps should be abovethe crown of the profile, and the end laps shouldbe supported on flat plates bridging the troughs.

5. Minimise the number of laps

Where possible reduce the number of end laps toa minimum by using full rolls of sheeting. The lapsshould be at least 150mm wide.

6. Attention to detail

The vapour control layers must be properly closed,sealed and fully integrated with wall structure,masonry, roof upstands, glazing heads, the roofperimeter and penetrations such as soil and ventpipes. Consider a clamped fixing arrangementwhich reduces the amount of air leakage. It isimportant that someone within the design teamprepares large scale details of how these closuresshould be formed, ensuring that the materials willbe readily available on site.

7. Good site practice.

This is probably the most important factor of all inachieving an effective vapour control layer. It isessential that the site tradesmen are fully aware of theimportance of the vapour control layer above warmand humid buildings, especially since theircompleted work will quickly be covered over as theroof is assembled.

Weather plays an important part, particularly whendealing with lightweight membranes which blow aroundin the wind. With lap details ensure a butyl tape isused, which can be used in damp and cold climates.Probond would meet this criteria. Finally, any minorscuffs and punctures through a completed vapourcontrol layer must be promptly repaired.

A Proctor Group

eight

CONDENSATION RISK ANALYSIS

The risk of condensation forming within a roof orwall construction can be predicted using themethod described in BS 5250. It is usual for thisanalysis to be undertaken on computer, and thisservice is provided by the A Proctor Group Tecline.

The starting point is to input the different layers ofthe construction, adding the thickness (mm), thermalresistivity (mK/W) and vapour resistivity (MNs/g.m)for each material. Next the internal conditions arerequired, preferably from site measurements.However, if they are not known, then the notionalconditions for different building types can be takenfrom Table 1 (page5). The external summer andwinter conditions averaged for a 60 day periodare normally taken from BS 6229.

The computer software computes the temperaturesto the different interfaces of the construction anddetermines the associated saturated vapourpressure (svp). The cumulative vapour resistanceis also computed, and where this is the same asthe svp for any interface, then condensation ispredicted. This can be plotted graphically as shownin the figure. Where the line meets the svp line,then condensation will occur.

If the analysis does predict condensation it isimportant to assess the long term risk to the fabric.Will the timber rot? Would the insulation becomeineffective? Could condensate drip into the buildingand stain ceiling tiles?

There are limitations using condensation risk analysisas it is simply a one dimensional steady state modelwith a number of assumptions. However, the resultscan highlight the potential risk for a givenconstruction and provide a timely warning.

The Importance of Vapour Control••••••••••SOME USEFUL REFERENCES

BS 5250: 2002 Control of condensation in buildings.

BS 5427: Part 1: 1996 The use of profiled sheetfor roof and wall cladding on buildings.

BS 5534: 2003 Slating and tiling: design.

BS 6229: 1982 Flat roofs with continuouslysupported coverings.

BS 4016: 1997 Specification for building papers(breather type)

The Building Regulations, Approved Document F2“Condensation in Roofs”

BRE Digest 270, Condensation in Insulated DomesticRoofs, February 1983.

BRE Digest 336, Swimming Pool Roofs, Minimisingthe Risk of Condensation, September 1988.

BRE Digest 369, Interstitial Condensation and FabricDegradation, February 1992.

BRE Report 262, “Thermal Insulation:Avoiding Risks”, Second Edition, 1994

NHBC Standards, Chapters 7.1 and 7.2

National Building Specification,Sections H30, H31, H60, H61, H65

CIRIA / BFRC, “Flat Roofing :Design and Good Practice”, 1993

FRCAB, “Roofing Handbook”,Information Sheets 6 and 7, June 1988

NFRC, “Profiled Sheet Metal Roofing and CladdingA Guide to Good Practice”, Second Edition, 1991

Dewpoint / Interfacetemperature graph

2 3 4 5 6

Ou

tsid

e

-5.0

oC

90.

0%RH

Insi

de

3

0oC

70.

0%RH

Temperature

Dew Point

LAYER 1 1.2mm Metal CladdingLAYER 2 0.5mm Breather MembraneLAYER 3 120.0mm Thermal InsulationLAYER 4 0.4mm Vapour Control LayerLAYER 5 30.0mm Acoustic InsulationLAYER 6 0.9mm Liner

G R O U P L T D

A Proctor Group

nine

The Importance of Vapour Control••••••••••DIFFERENT TYPES OF MEMBRANE TOCONTROL WATER VAPOUR

The A Proctor Group is unique in that they supplytwo different “families” of membranes to controlwater vapour within roof and wall constructions,each serving a different purpose.

The Vapour Control Layer is a continuous membranelaid on the warm side of the insulation to reducethe amount of moist air escaping into the roof orwall construction.

The Breather Membrane allows any moist air withinthe construction to pass out of the building whileoffering some weather protection from driving rainand snow.

Table 2

TO SUMMARISE,THE KEY POINTS ARE

The vapour control layer must be:

• on the warm side of the insulation

• continuous

• treated with respect

• sealed at all laps

• sealed to and integrated with other elementssuch as wall heads, glazing heads, glazing upstands and soil and vent pipes.

The breather membrane must be:

• behind the external weathering face

• continuous

• able to shed water out of the building

• of a high moisture vapour permeability

Membrane Type Allows passage of water Go to page

Water as a liquid Water as a gas

Vapour Control Layer No No 10

Breather Membrane No Yes 17

NBS SPECIFICATION

Full NBS Specifications are available on the website or alternatively contact our Techdesk.Tel No: 01250 872261Web: www.proctorgroup.com

A Proctor Group

ten

Product Selector•••••••••••••••••••••••

Table 3

Profoil

861

UVStabilised

FireResistant

lowhumidity

moderatehumidity

highhumidity

ProcheckStandard

300

850

ProcheckPremier

500

859

ProcheckPremier FR

400

835

ProfoilFS1

862Code

Page Ref:

Reinforced

Translucent

AluminiumFoil

CorrosionResistant in

chlorineenvironments

PRODUCTPR

OPE

RTI

ESA

PPLI

CATI

ON

1111 11 12 12

Vapour Control Layers

Table 3

A Proctor Group

eleven

Membrane Information Sheets••••••••••••••

Physical Properties Test Method Result

Nominal Weight 152 g/m2

Nominal Thickness 0.29 mmTensile Strength BS 4415 Part 2along the roll 3.4 kN/macross the roll 2.4 kN/mNail Tear Resistance MOAT No: 27 : 5.4.1along the roll 60 Nacross the roll 60 NWater Vapour Resistance ISO 9932 : 1990 336 MNs/gMoisture Vapour Transmission Rate ISO 9932 : 1990 0.61g/m2/day

Procheck Standard 300A lightweight reinforced polyethylene vapour control layer for use within roof and wall constructions to prevent warm,moist air escaping from inside the building and condensing within the insulation. The woven polypropylene multifilamentscrim reinforcing provides good resistance to tears and punctures.

Roll Specification:

Standard Roll Size: 50m x 2.0m

Weight: 15 kg/roll

Colour: Translucent

Product Code: 850

Procheck Premier 500A strong reinforced polyethylene vapour control layer with good vapour resistance.The woven extruded polypropylene multifilament scrim reinforcing provides improved nail tear resistance. The sheetis translucent to ease the installation and later inspection of support arrangements, and is the grade utilised by manyleading system manufacturers.

Roll Specification:


Weight: 23.6 kg/roll

Colour: Translucent

Product Code: 859



Nominal Thickness 0.37 mmTensile Strength BS 4415 Part 2along the roll 6.2 kN/macross the roll 5.8 kN/mNail Tear Resistance MOAT No: 27 : 5.4.1along the roll 180 Nacross the roll 170 NWater Vapour Resistance ISO 9932 : 1990 533 MNs/gMoisture Vapour Transmission Rate ISO 9932 : 1990 0.39 g/m2/day

ProfoilA heavyweight reinforced vapour control layer with aluminium foil core to give a high water vapour resistance. Thewoven extruded polypropylene multifilament scrim reinforcement gives good resistance to tears and punctures. Thealuminium foil is protected on both faces by polyethylene for corrosive situations, such as chlorine in swimming pools.

Roll Specification:


Weight: 31 kg/roll

Colour: Blue (top)Reflective Silver (bottom)

Product Code: 861



Nominal Thickness 0.4 mmTensile Strength BS 4415 Part 2along the roll 7.3 kN/macross the roll 7.3 kN/mNail Tear Resistance MOAT No: 27 : 5.4.1along the roll 215 Nacross the roll 182 NWater Vapour Resistance ISO 9932 : 1990 Greater than

533 MNs/gMoisture Vapour Transmission Rate ISO 9932 : 1990 Less than

0.005 g/m2/day

A Proctor Group

twelve

Membrane Information Sheets•••••••••••••••



Nominal Thickness 0.5 mmTensile Strength: 56 days aged @ 60oC BS 2782:320Aalong the roll 6.0 kN/macross the roll 4.0 kN/mNail Tear Resistance MOAT No: 27 : 5.4.1along the roll 110 Nacross the roll 90 NBurst Strength, wet/dry BS 3137 500 kN/m2

Water Vapour Resistance BS 3177 0.17 MNs/gMoisture Vapour Permeability BS 3177 1100 g/m2/dayResistance to Water Penetration(Eosin Test) BS 4016 PassFire Resistance to Spread of Flame DIN 4102 B2

CladshieldA single layer spun bonded polypropylene breather membrane designed for use primarily in lightweight industrialcladding systems. During site construction Cladshield is satisfactory if left open in fair weather prior to covering, butit cannot be regarded as temporary weather protection against wind driven rain and snow. Cladshield can also beused as a separation layer between some types of insulation and single ply membranes.

Roll Specification:

Standard Roll Size: 100m x 1.6m100m x 3.0m

Weight: 16 kg/roll, 30 kg/roll,

Colour: Grey



Nominal Thickness 0.45 mmTensile Strength BS 4415 Part 2along the roll 10.5 kN/macross the roll 9.3 kN/mNail Tear Resistance MOAT No: 27 : 5.4.1along the roll 150 Nacross the roll 150 NWater Vapour Resistance ISO 9932 : 1990 Greater than

20,600 MNs/gMoisture Vapour Transmission Rate ISO 9932 : 1990 Less than

0.01 g/m2/day

Profoil FS1A heavyweight reinforced vapour control layer with aluminium faces and good fire resistance properties. The multifilamentpolyester scrim reinforcement gives good resistance to tears and punctures. The exposed aluminium foil on both facesgives a high water vapour resistance and ensures low flame spread characteristics.

Roll Specification:


Weight: 23 kg/roll

Colour: Reflective Silver

Product Code: 862



Nominal Thickness 0.37 mmTensile Strength BS 4415 Part 2along the roll 6.2 kN/macross the roll 6.1 kN/mNail Tear Resistance MOAT No: 27 : 5.4.1along the roll 170 Nacross the roll 160 NWater Vapour Resistance ISO 9932 : 1990 428 MNs/gMoisture Vapour Transmission Rate ISO 9932 : 1990 0.48 g/m2/dayFire Resistance to Spread of Flame DIN 4102 B2

Procheck FR 400A strong reinforced polyethylene vapour control layer with good vapour resistance. The woven polypropylenemultifilament scrim reinforcing provides improved nail tear resistance. The addition of fire resisting compounds meansthat the material will not readily ignite and, although it will melt, will not continue to burn in small fires.

Roll Specification:


Weight: 24 kg/roll

Colour: Opaque

Product Code: 835

A Proctor Group

thir teen

Roll Specification:

Standard Roll Size: 100m x 1.6m100m x 3.0m

Weight: 16 kg/roll, 30 kg/roll,

Colour: Grey

Roll Specification:


Weight: 23 kg/roll

Colour: Reflective Silver

Product Code: 862

Roll Specification:


Weight: 24 kg/roll

Colour: Opaque

Product Code: 835

Laps

Lay the vapour control layer loose, flat and withoutwrinkles. Laps should be preferably sealed withtwo continuous runs of 15mm wide Probond RGtape. (see photo above) The minimum width of alap should be 150mm. Adhesive PVC should notbe used for sealing and jointing laps in vapourcontrol layers.

Puncture Damage

Where puncture damage is unavoidable, applygood sized patches over the puncture, ensuringthat there is a continuous bead of tape all the wayaround the hole. For small scuff type damage ofless than 25mm as an alternative Profoil Tape maybe used.

Details

Attention to detail is important. The vapour controllayer needs to be continuous and particular careis required sealing around penetrations and at theperimeters where roofs and walls meet.

INSTALLATION OF VAPOURCONTROL LAYERS

Delivery and Site Handling

Rolls of vapour control layers are delivered to sitewith tape identifying the product grade ormembrane, or overprinted, clearly identifyingproduct name and grade. Rolls should be storedflat or upright on a clean, level surface and keptunder cover.

Weather Conditions

Laying lightweight membranes in highwind conditions is difficult and appropriateprecautions should be taken during installation.

Preparation of the Base

Before installing the vapour control layer ensurethat the surfaces to be covered are firmly fixed,clean, dry and smooth.

Details and Installation••••••••••••••••••

25mm 25mm150mm Min

A Proctor Group

four teen

Details and Installation••••••••••••INSTALLATION OFBREATHER MEMBRANES

Delivery and Site Handling

Rolls of breather membrane are delivered to site,individually wrapped in a polythene sleeve.The sleeve has an identification tape with ProductName and Supplier Information.

Rolls may be stored flat or upright on a clean, levelsurface and kept under cover.

Metal roofs

For sheet roof applications, the breather membraneshould be laid either horizontally or vertically upthe slope such that it forms a continuous membraneover the entire area of the roof, allowing any waterto drain down to the gutters.

On a low pitch metal roof, the draping of thebreather membrane between purlins can result inponding which is unsatisfactory and should beavoided. It is preferable for the breather membraneto be fully supported to give a clear drainage path.If this is not practical on low slope roofs then thelaps should be taped using Proctor BreatherAdhesive Tape to prevent water finding its waydown onto the insulation below.

At penetrations, such as vent pipes and rooflights,an additional piece of breather membrane shouldbe laid upslope and taped in position, to channelwater away to each side of the opening.

Laying lightweight membranes in high windconditions is difficult and appropriate precautionsshould be taken during installation.

Wall Cladding

For vertical Metal Cladding Application the breatherMembrane should be installed on the outer side ofthe insulation. The membrane is usually installedvertically with laps of 100mm minimum as workprogresses.

Detailing of the membrane is important to ensurethat the building is temporarily protected from rainduring installation and that condensation will drainaway once the external sheeting has been applied.

Details

Attention to detail is important.Avoid blockages where possible that wouldotherwise prevent the free drainage of water.A preferred specification is the use of an eavescarrier.

A Proctor Group

f i f teen

Key point to watch:Ensure Vapour Control Layer iscontinuous and all laps andpenetrations are sealed effectively

BUILT UP METAL ROOF/METAL SIDE CLADDING

Figure 5 - pipe penetrationFigure 4 - Verge detail

Key point to watch:1. Ensure the Vapour Control Layer isfully sealed to the Top Hat withProbond Tape Also ensure the Top Hatis sealed to the pipe using a suitablesealant.

2. Ensure Breather membrane is turnedup around pipe to prevent condensatedraining into roof void.

Key point to watch:The lap between thevapour control layers should be sealedwith two continuous runs of15mm wide Probond Tape.

Figure 2 - Ridge

Figure 3 - Eaves gutter

Key points to watch:1. The vapour control layer in the wallneeds to be effectively sealed to thevapour control layer in the roof.

2. The roof breather membrane drainsfreely into the gutter.

Metal Cladding

Metal Lining

Thermal Insulation

Breather Membrane

Vapour Control Layer

Breather Membrane


BreatherMembrane

Top Hat

Vapour ControlLayer

Breather Membrane


Breather Membrane Vapour Control Layer

Preferred Details••••••••••••••••••••••••

Figure 1 - Typical section

G R O U P L T DReg No. FM45117

ISO 9001

APG5450

www.proctorgroup.com

cl/sfb (13.9) ln6 a comprehensive technical guide technical guide.pdf · water vapour pressure ......

Documents