canada commercial protected membrane roof installation ......protected membrane roof installation...

Protected Membrane Roof Installation Guidelines

O V E R V I E W 2

G L O S S A R Y 4

C O M P O N E N T S 6

STYROFOAM™ Brand Extruded Polystyrene Foam Insulation 6

Fabric 8

Ballast 10

Pavers 12

All Other Components 13

C O N D I T I O N S , I S S U E S A N D R A T I N G S 15

Special Conditions and Issues 15

Cold Rain Phenomenon 15

Moisture Absorption 16

Dimensional Stability 16

Vegetative Roof Design 17

Finding Leaks in a PMR 18

Low Temperature Applications 18

High Temperature Installation 19

Membrane Seam Failure 19

Plant Growth on PMR Assemblies 19

Fire and Wind Ratings 20

Overview 20

Test Methods 20

ULI Hourly Fire Resistance Ratings for PMR – Steel Deck 21

ULI Hourly Fire Resistance Ratings for PMR – Concrete Deck 22

ULI Hourly Fire Resistance Ratings for PMR – Other 22

ULC Hourly Fire Resistance Ratings for PMR – Metal Deck 23

ULC Hourly Fire Resistance Ratings for PMR – Concrete Deck 23

FM Hourly Fire Resistance Ratings for PMR 23

FM Class 1 Fire and Wind Uplift 23

Canada C O M M E R C I A L

®™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow


OV

ER

VIE

W

2

Protected membrane roofing’sbreakthrough contribution toflat roof technology was theincorporation of an “upside-down” approach to insulatingthe roof: placing the insulationon top of the waterproof mem-brane to improve the membrane’seffectiveness and the insulation’sefficiency.

This advancement was madepossible in large part by the useof STYROFOAM™ BrandExtruded Polystyrene (XPS) FoamInsulation, whose closed-cell,water-resistant qualities haveproven to be a key componentin protected membrane roof(PMR) systems.

A conventional roof placesthe membrane on top of theinsulation, leaving the mem-brane vulnerable to extremetemperature changes, freeze-thaw conditions and physicalabuse from heavy foot traffic(Figure 1).

The PMR system places theinsulation on top of the mem-brane, protecting the roofingmembrane from extreme tem-perature changes and physicalabuse (Figure 2).

The main difference betweenPMR and conventional roofingis the sequence in which thematerials are applied. The keyto the PMR system is that theinsulation is placed on top ofthe waterproofing membrane.This configuration protects themembrane, resulting in excellentlong-term performance anddurability.

Figure 1: Conventional Roof With Membrane Abovethe Insulation (depending upon building and climateconditions, a vapor barrier may also be used)

Figure 2: PMR With Membrane Below the Insulation

Ballast

FilterFabric

STYROFOAM™ Brand FoamInsulation

Membrane

Deck

Membrane


Deck

OverviewC H A N G I N G T H E S E Q U E N C E


OV

ER

VIE

W

3

OverviewC H A N G I N G T H E S E Q U E N C E

Advantages of PMR

All flat roof assemblies consistof the same basic elementsassembled in a seemingly logicalorder: a deck (composed of wood,metal or concrete), covered withinsulation and topped with awaterproofing membrane. A protected membrane roof canemploy the same elements, butthe membrane is positionedunder the insulation, offeringexceptional long-term perform-ance and durability.

PMR assemblies: • Maintain the membrane at a

nearly constant temperature,close to the temperature of the building’s interior; thisminimizes the stresses on themembrane by reducing theharmful effects of freeze-thawcycling, thermal cycling andexcessive heat

• Protect the membrane fromweathering, foot traffic and othertypes of physical abuse – bothduring and after construction

• Allow year-round constructionsince the roof is waterproofedfirst, then insulated

• Permit easy removal andre-installation of the ballastand insulation for makingrepairs or for constructingadditional stories. In addition, a protected membrane roofprovides an environmentallypreferred option to reuse theinsulation

• Allow for a range of ballastoptions – stone, precast pavingslabs, soil and plantings for avegetative roof, interlockingstone or concrete – dependingon use and aestheticconsiderations

• Are compatible with a range of membrane types

• Eliminate the need for aseparate vapour retarder

PROVIDE DURABILITY AND PROTECTION

With the membrane positionedunder the insulation, the choiceof insulation becomes an impor-tant consideration. The insulationmust be able to withstand wetenvironments (without sacrificinginsulation performance) andfoot traffic during and after construction, while continuingto perform over time.

Because of its durability andexcellent moisture-resistant qualities,STYROFOAM™ Brand ExtrudedPolystyrene Foam Insulationdelivers exceptional performancein roofing and plaza applications.• Provides excellent moisture

resistance and long-termR-value (RSI)*

• Offers exceptional durability to extend the life of the plazaor roof

• Protects the membrane againstweathering, physical abuseand damage

• Maintains the membrane at arelatively constant temperature

• Controls dew point location

*R means resistance to heat flow. The higher the R-value (RSI), the greater the insulating power.

Absorption: the ability of amaterial to absorb quantities ofgases or liquids, such as moisture.

Accelerated Weathering: anexperimental test where a materialis exposed in a controlled environment to various elements(heat, water, condensation orlight) to magnify the effects of weathering. The material’sphysical properties are measuredbefore and after the process toidentify any detrimental effectsof weathering.

Aggregate: rock, stone, crushedstone, crushed slag or water-worn gravel used for ballasting a roof system.

Aging: the effect on materialsexposed to an environment for a defined time.

Alligatoring: the cracking of theexposed bitumen on a built-uproof, producing a pattern of crackssimilar to an alligator’s hide.

Asphalt: a dark brown or blacksubstance left as a residue whenprocessing crude oil or petroleum.Asphalt may be further refinedto conform to various roofinggrade specifications.

Asphalt Emulsion: a mixture ofasphalt particles and an emulsi-fying agent, such as bentoniteclay and water.

Ballast: an anchoring material,such as stone or precast concrete pavers, used to holdinsulation and/or roof mem-branes in place.

Base Ply: the bottom ply ofroofing in a roof membrane orroof system.

Base Sheet: an impregnated,saturated or coated felt placed asthe first ply in some multi-plybuilt-up and modified bitumenroof membranes.

Blocking: sections of wood builtinto a roof assembly, usuallyattached above the deck andbelow the membrane or flashing,used to stiffen the deck aroundan opening, act as a stop forinsulation, support a curb or toserve as a nailer for attachmentof the membrane and/or flashing.

Built-up Roof (BUR) Membrane:a continuous, semi-flexible multi-ply roof membrane, made up ofplies or layers of saturated felts,fabrics or mats with bitumen inbetween.

Cant Strip: a beveled or triangular-shaped strip of wood or othersuitable material used to transi-tion from the horizontal surfaceof a roof deck or rigid insulationto a vertical surface.

Caulking: sealing and makingweather-tight the joints, seamsor voids between adjacent unitsusing a sealant.

Compatible Materials: two or more substances that can be mixed, blended or attachedwithout separating, reacting oraffecting the materials adversely.

Condensation: the conversionof water vapour or other gas toliquid state as the temperaturedrops or atmospheric pressurerises. (Also see Dew Point.)

Counterflashing: formed metalsheeting secured on or intoanother surface used to protectthe upper edge of the membraneor underlying metal flashingand associated fasteners fromexposure to the weather.

Curb: a raised roof location relatively low in height.

Dead Load: permanent non-moving load that results from theweight of a building’s structuraland architectural components,mechanical and electrical equipment, and the roof assembly itself.

Deck: a structural component ofthe roof of a building designedto safely support the design deadand live loads, including theweight of the roof systems, andthe additional live loads requiredby the governing building codes.Decks are either non-combustible(e.g., corrugated metal, concreteor gypsum) or combustible (e.g.,wood plank or plywood) and arethe substrate used to apply theroofing or waterproofing system.

Design Load: load specified in building codes or standardspublished by federal, provincial,county or city agencies, or inowners’ specifications to be used in the design of a building.

Dew Point: the temperaturewhere water vapour condenses in cooling air at the existingatmospheric pressure and vapour content. Cooling at orbelow the dew point will causecondensation.

Dynamic Load: any load that isnon-static, such as a wind loador a moving live load.

Fabric: a woven cloth or materialof organic or inorganic filaments,threads or yarns. Can be used as a reinforcement in certainmembranes and flashings orused in a protected membraneroof application to reduce theballast requirements.

Flashing: materials used toweatherproof or seal the roofsystem edges at perimeters, penetrations, walls, expansionjoints, valleys, drains and otherplaces where the roof covering is interrupted or terminated.

Gravel Stop: a low profile,upward-projecting metal edgeflashing with a flange along theroof side, usually formed fromsheet or extruded metal. Installedalong the perimeter of a roof toprovide a continuous finishededge for roofing material.

GL

OS

SA

RY

4

Glossary


GL

OS

SA

RY

5

Glossary

Humidity: the amount of moisture contained in theatmosphere. Generally expressedas percent relative humidity (% RH). It is the ratio of theamount of water vapour actuallypresent in the air, compared tothe maximum amount that theair could contain at the sametemperature.

Inverted Roof MembraneAssembly (IRMA): same asprotected membrane roof (PMR)assembly, where a closed-cellinsulation (e.g., STYROFOAM™

Brand XPS Foam Insulation) andballast are placed over the roofmembrane.

Live Load: temporary load that the roof structure must bedesigned to support, as requiredby governing building codes.Can include people, installationequipment, vehicles, wind,snow, ice or rain, etc.

Loose-laid Membrane: mem-brane that is not attached to thesubstrate except at the perimeterof the roof and at penetrations.Typically, a loose-laid membraneis held in place with ballast.

Mechanically FastenedMembrane: membrane that isattached at defined intervals tothe substrate, using various fas-teners and/or other mechanicaldevices.

Membrane: a flexible orsemi-flexible material that water-proofs (excludes water) a roof.

Parapet Wall: that part of aperimeter wall immediatelyadjacent to the roof, whichextends above the roof.

PMR: protected membrane roof.

Positive Drainage: the drainageprofile of a deck, consideringthe roof slope and loadingdeflections to ensure the roofdeck drains within 48 hours ofrainfall during ambient dryingconditions.

Ridge: highest point on the roofwhere two roof areas intersect.

Roof Assembly: an assembly of interacting roof components(includes the roof deck, vapourretarder [if present], insulationand roof covering).

Roof Slope: the angle a roofsurface makes with the horizon-tal. Typically expressed as a ratioof rise to run, such as 4:12, or asa percent.

Square: 100 ft2 (9.29 m2) of roofarea.

Substrate: the surface on whichthe roofing or waterproofingmembrane is applied (e.g., thestructural deck or insulation).

Vapour Retarder: a materialthat restricts the movement ofwater vapour.

Wind Uplift: the force caused bythe deflection of wind at roofedges, roof peaks or obstructions,causing a drop in air pressureimmediately above the roof surface (e.g., suction). Uplift mayalso occur from air movementfrom underneath the roof deck,causing the membrane to balloonand pull away from the deck.

Description

STYROFOAM™ Brand ExtrudedPolystyrene (XPS) Foam Insulationis a rigid, closed-cell insulation,ideally suited and designed forPMR installations. Because ofthe properties imparted duringthe extrusion process combinedwith the hydrophobic nature of polystyrene, STYROFOAM™

Brand Insulation has a highresistance to both water andwater vapour, providing demon-strated long-term mechanicaland thermal performance.

The boards are available in a range of thicknesses, densitiesand edge treatments.


CO

MP

ON

EN

TS

–

S

TY

RO

FO

AM

™ B

ra

nd

E

xt

ru

de

d P

oly

st

yr

en

e F

oa

m In

su

la

tio

n

6

ComponentsS T Y R O F O A M™ B R A N D E X T R U D E D P O L Y S T Y R E N E F O A M I N S U L A T I O N

STYROFOAM™ Brand ROOFMATE™

An extruded polystyrene foam insulationproviding excellent moisture resistance,durability and long-term R-value (RSI).Ideal for installation above waterproofingor roofing membranes in PMR applications.

STYROFOAM™ Brand HIGHLOAD 40, 60 and 100An extruded polystyrene foam insulationboard with high compressive strengthdeveloped specifically for in-groundapplication and freezer floors. The prod-ucts are also well-suited for plaza decksand protected membrane roofs that mustwithstand heavy traffic.


CO

MP

ON

EN

TS

–

S

TY

RO

FO

AM

™ B

ra

nd

E

xt

ru

de

d P

oly

st

yr

en

e F

oa

m In

su

la

tio

n

7

ComponentsS T Y R O F O A M™ B R A N D E X T R U D E D P O L Y S T Y R E N E F O A M I N S U L A T I O N

Function

Provide thermal properties:STYROFOAM™ Brand ExtrudedPolystyrene Foam Insulation hasa high aged thermal resistance(R-value or RSI) when comparedwith competitive roof insulations.

Provide membrane protection:By installing the insulation overthe membrane, the membrane is kept at a relatively constanttemperature year-round and protected from weathering,mechanical damage and abuse.

Specification

The insulation shall meetCAN/ULC S701 Type 4.

Install required thickness ofSTYROFOAM™ Brand ExtrudedPolystyrene Foam Insulationunbonded over the roof mem-brane. Install a slip or separationsheet over the membrane if themembrane is coal tar or Type 1or 2 asphalt, or if required bythe membrane manufacturer.

Butt boards tightly togetherwith a maximum 3/8" (9 mm)gap between boards, staggeringend joints. The recommendedstagger between each board is 2'(600 mm). However, in caseswhere boards have been cut tofit, maximize the stagger wherepossible. At a minimum, eachboard should have at least an 8"(200 mm) stagger.

Bevel edges to fit closely tocant slopes.

Fit around protrusions andobstructions with a maximum3/4" (19 mm) gap to minimizeheat loss.

Multi-layer foam installation:• The bottom layer of insulation

(the layer directly on themembrane) must be at least 2" (50 mm) thick.

• The bottom layer must be thethickest or, at minimum, equalto the top layer (e.g., 3" [75 mm]bottom and 3" [75 mm] top).

• Lay successive layers of insulation unbonded or unadhered.

• Stagger or offset all joints fromthose of the underlying layer.

Installation Notes

Protect insulation from physi-cal damage.

Handle boards carefully to pre-vent damage during installation.

Always wear protective eyewearand gloves when handling andcutting insulation.

Always store insulation awayfrom direct sunlight, particularlywhen storing for an extendedtime. Cover with a light-colouredopaque tarp for protection fromsolar radiation. The surfacedegradation caused by ultraviolet(UV) light will have no measurableeffect on the insulating valueunless the deterioration isallowed to continue until actualthickness is lost.

Always check the compatibilitywith other products that maycome in direct contact with theinsulation, particularly thosecontaining solvents. Preventivecare must be taken, such asallowing the solvents to evapo-rate, providing a slip sheet orpainting the surface of the insu-lation with white latex paint.Always brush off any surfacedust before applying white latexpaint on the insulation.

STYROFOAM™ Brand ExtrudedPolystyrene Foam Insulation iscombustible and may constitutea fire hazard if improperly usedor installed. The insulation con-tains a flame-retardant additiveto help inhibit ignition fromsmall fire sources. During ship-ping, storage, installation anduse, this material should not beexposed to open flames or otherignition sources.

®™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow**This is an illustration of a typical detail. Responsibility for actual design remains that of the designer.

CO

MP

ON

EN

TS

–

F

ab

ric

8

ComponentsF A B R I C

Description

Ballast reduction fabric, commonly known as filter fabric, is used in PMR installa-tions between the ballast andinsulation. This water-permeablematerial must have proven long-term weather resistance, be strongenough to withstand trafficabuse and prevent displacementof the insulation under flotationconditions.

Function

• Prevent fines from penetratingbetween insulation boards

• Raft the insulation together to reduce ballast requirements

• Reduce mechanical damage to insulation

• Allow easy stone removal ifaccess is required to flashings,insulation and/or membrane

Overlap all edges a minimumof 12" (300 mm). If a small piecehas to be used, minimum sizeshould be 8' x 8' (2.5 m x 2.5 m).

Slit fabric to fit over any roofpenetrations. Cut around roofdrains and other openings(Figure 4).

Specification

Apply fabric unbonded andshingle fashion over the installedinsulation (Figure 3).

Ballast

Filter Fabric


Membrane

Deck

STYROFOAM™Brand FoamInsulation

Ballast

Filter Fabric

Membrane

Deck

Drain Body Drain Line WithInsulation Wrap

Drain Cap

Exterior Drain Body

Figure 3: Fabric Placement**

Figure 4: Drain Detail With Fabric**

IMPORTANT: When schedulingor weather conditions delayinstallation of plaza, patiodeck or garden roof PMRareas, care must be taken toensure that dark-colouredproducts, such as black plasticdrainage boards (dimpleboards) or dark fabric, are notplaced over the insulationand then left exposed. Dark-coloured products can lead toextremely high surface tem-peratures, increasing thepotential for distortion ofrigid foam boards.

If STYROFOAM™ BrandExtruded Polystyrene FoamInsulation is already installed,cover it with a white opaquepolyethylene film to protect itduring the delay. Otherwise,schedule the insulation instal-lation for a time when theentire installation process can be completed in a timelymanner.


CO

MP

ON

EN

TS

–

F

ab

ric

9

ComponentsF A B R I C

Installation Notes

Store all materials in dry, protected areas in an uprightposition.

Dow experience has shownthat when STYROFOAM™ BrandExtruded Polystyrene FoamInsulation is exposed to bothdirect sunlight and an outdoorair temperature over 90°F (32°C),distortion of the foam can occurin as little as 30 minutes when aheavy, dark-coloured fabric is overthe insulation. To prevent thisphenomenon during hot weather,temporarily place white opaquepolyethylene film on the fabricuntil the ballast is laid (or use a

white filter fabric).Install the fabric unadhered

directly over the foam insulation.Wetting the fabric sometimeshelps secure it until the ballastcan be applied.

SupportingDocumentation

Blueprint 501a: “ProtectingSTYROFOAM™ Brand InsulationBelow Dark Roofing Membranesand Fabrics”

Extend the fabric up the roof perimeter cants and roofprotrusions by at least 3" (75 mm)above the top level of the ballast(typically about a 6" [150 mm]upturn) and place it loose underthe metal counterflashings (Figure 5).

Fabrics, such as Fabrene V.I.E.,†

should meet or exceed the guidelines listed in Table 1.

For a complete list of accept-able filter fabrics, contact a Dowrepresentative.

Deck

Membrane

Ballast

Filter Fabric

STYROFOAM™

Flashing

8' 6"

Ballast at 22 lbs/ft2 to 4 Feet

in from Parapet for Wind Uplift

Around Entire Perimeter of Roof

Brand Foam Insulation

Figure 5: Parapet Detail With Fabric**

T A B L E 1

**This is an illustration of a typical detail. Responsibility for actual design remains that of the designer.

†Fabrene V.I.E. is a registered trademark of PGI - Fabrene Inc.

Specification Guidelines

Criteria Test Method Units Value

Unit Weight ASTM D1910 oz/yd2 4.0 (max)

Notch Tear lbMD ASTM D2262 7.0 (min)CD 7.0 (min)

Tensile Grab lbfMD ASTM D1682 70 (min)CD 60 (min)

Elongation @ break ASTM D1682 % 15 (min)

UV Resistance Approved for outdoor use

Material Woven polyolefin preferredto promote run-off


CO

MP

ON

EN

TS

–

B

alla

st

1 0

Description

Crushed stone or washed,rounded riverbed rock, with a 1"(25 mm) clear size, free of finesor stones smaller than 5/8" (15 mm)or larger than 1-3/8" (35 mm).Most stones should be 3/4" to1-1/4" (19 mm to 32 mm) size.

Function

Prevent uplift and preventflotation: Ballast is required toprevent negative flotation and isbased on the total thickness ofSTYROFOAM™ Brand ExtrudedPolystyrene Foam Insulation andthe type of membrane used.

Adhered membrane (e.g.,membrane attached to deck):When a suitable UV-resistant filterfabric is used over a membraneattached to the deck, the amountof required ballast is 10 lb/ft2 (50kg/m2) regardless of the insulationthickness, except around theperimeter and penetrations, and inareas of high winds. See Table 2 foramount of ballast required forperimeters and penetrations, aswell as PMR assemblies installedwithout a fabric.

It is critical that the membrane isproperly attached to the deck whenusing 10 lb/ft2 (50 kg/m2) ballastand a suitable filter fabric to preventthe possibility of any ballast fallingunder the membrane during timesof ponding and air infiltration.

Areas of extra ballasting: Extraballast, required to overcome highwind loads and restrain insulationduring heavy rainstorms, should beconsidered in the following locations:• Perimeter edge – 4' (1.2 m)

wide band running along theperimeter edge of the roofinsulation.

• Penetrations through theinsulation – 2' (0.6 m) wideband around any roof penetra-tion greater than 4' (1.2 m) inany direction (e.g., skylights,equipment pads, etc.).

• Corners – Concrete paversand/or parapets may berequired. See “Pavers” on page12 for additional information.

• Building exposure – Considerthe surrounding terrain and itspotential effect on overallwind exposure (e.g., nearbywoods versus shorelines).

Prevent wind scouring: Thewind performance of stone-ballasted PMR assemblies hasbeen excellent. Only a few iso-lated minor scouring problemshave occurred, typically limitedto small areas in and aroundcorners. In these few cases, theballast has been blown inboundby about 4' (1.2 m) and piled upon the filter fabric, creatingadditional weight. In theseinstances, concrete paversshould be considered. See“Pavers” on page 12 for details.

Prevent UV degradation ofthe insulation: Most PMR appli-cations use a filter fabric thattypically incorporates a UV sta-bilizer. However, if no fabric isused, the insulation must betotally covered by the ballast toprevent UV degradation. Thequality of the ballast is criticalin these types of applications.Too small (fines not more than10 percent of mix) and thestones may work into the insula-tion joints or be moved by thewind; too large and the ballastmay not provide adequate coverto protect from UV light.

Provide a Class A fire-resistantroof cover: Class A roof covering,as defined by ULC S107, ULI 790and ASTM E108. (See “Fire andWind Ratings” on page 20for details.) The requirements forClass A roof construction coverthe performance of roof assem-blies and roof covering materialswhen exposed to a fire originatingfrom sources outside a building.The stone ballast provides theClass A fire rating.

ComponentsB A L L A S T

T A B L E 2

Required Ballast Around Perimeters and Penetrations, and for Standard PMR (Without Fabric)

Insulation Thickness, inch (mm) Required Weight of Ballast, Approximate Thickness of Ballast,lb/ft2 (kg/m2) inch (mm)

Up to 2 (50) 12 (60) 1-1/2 (40)

3 (75) 17 (84) 2-1/4 (60)

4 (100) 22 (108) 3 (75)

5 (125) 27 (132) 3-1/2 (90)

6 (150) 32 (156) 4-1/4 (105)

7 (175) 37 (180) 5 (125)

8 (200) 42 (204) 5-1/2 (140)

CO

MP

ON

EN

TS

–

B

alla

st

1 1

ComponentsB A L L A S T

Specification

Sound, hard, washed stone orgravel, freeze-thaw resistant,with a 1" (25 mm) clear size, freeof fines or stones smaller than5/8" (15 mm) or larger than 1-3/8"(35 mm). Most stones shouldbe 3/4" to 1-1/4" (19 mm to32 mm) size.

PMR (without fabric): Spreadstone ballast uniformly overinstalled insulation to provideminimum weight or thickness(Table 2).

PMR (with fabric): Spreadstone ballast uniformly overinstalled fabric and insulation toprovide minimum weight of 10lb/ft2 (50 kg/m2) or 1-1/2" (38 mm)thickness.

Note: Use either weight or thickness,but not both.

Spread additional ballastaround the roof perimeter for awidth of 4' (1.2 m) to increaseballast weight or thickness. Referto Table 2 for either weight orthickness, depending on thethickness of insulation installed.

Spread additional ballast aroundany penetration for a width of 2'(0.6 m) if the penetration isgreater than 4' (1.2 m) in anydirection.

Installation Notes

Make sure that proper provi-sions have been specified to sealopenings in the roof deck andany perimeter blocks. This willprevent air from getting belowthe roofing membrane andbillowing it.

For PMR installations withouta fabric, ensure that the ballastdoes not contain too manysmall stones (fines not morethan 10 percent of mix) as theymay work into the insulationjoints or be moved by the wind.Conversely, too many largestones may not provide adequatecover to protect the insulationfrom UV light where a fabric isnot used.

Store ballast in dry, protectedareas and protect it with breath-able tarps on top and side surfaces.

If ballast has been moved bywind scour, repair is simple. Justreplace the insulation (if neces-sary), re-lay the filter fabric andreplace the ballast. A small pavercan be added, if required.

If a gravel stop is required, theheight of the gravel stop at abuilding perimeter should be atleast 2" (50 mm) from the top ofthe ballast.

SupportingDocumentation

National Research Council ofCanada report by Kind andWardlaw. Report on PMR assembliesusing a 30' x 30' (9 m x 9 m)wind tunnel, with various ASTMgradation/sizes of ballast. (Seereports NRC LTR-LA 269, NRCLTR-LA 234, NRC No. 15544.)

ANSI/SPRI RP-4 Wind DesignStandard for Ballasted Single-PlyRoofing Systems (for mechani-cally attached and loose-laidPMR)

ASTM D448 StandardClassification for Sizes ofAggregate for Road and BridgeConstruction

ANSI/ASCE 7 MinimumDesign Loads for Buildings andOther Structures (includes BasicWind Speed Map)

CO

MP

ON

EN

TS

–

P

av

er

s

1 2

ComponentsP A V E R S

Description

Concrete slab pavers or inter-locking pavers can be used tosupplement or replace conven-tional stone ballast requirementsand create a surface for rooftopdecks, walkways, terraces, gardensand similar applications.

Note: For structural plaza deckdesign, such as for parking decksand other high-traffic areas, thedesign is the responsibility of anarchitect and/or structural engineer.

Function

Note: For additional information,see “Ballast” on page 10.

Narrow roof walkways foraccess: Pavers can be placed tofacilitate access to rooftopequipment.

Prevent wind scouring: Inexposed areas or areas of highwinds, pavers may be required.In certain conditions, the paversshould be strapped togetherusing galvanized or stainlesssteel straps, mechanically fas-tened to each paver.

Perimeter ballast: Additionalballast is required around thebuilding perimeter in a PMRdesign. Depending on thedesign, pavers can be installedinstead of conventional stoneballast.

Plaza deck design: For light traffic requirements, the stoneballast can be replaced with concrete pavers completely. Inmany cases, the pavers must beraised from the surface of thefabric and insulation. See“Installation Notes” for details.

Specification

PAVERSConcrete pavers shall be man-

ufactured from minimum 3,000lb/in2 (210 kg/cm2) concretewith a minimum weight of 18lb/ft2 (88 kg/m2).

Pavers should be placed onpedestals to ensure a “diffusionopen” design. The pedestal can be:• 1" (25 mm) thick insulation

cut into 6" (150 mm) squareblocks and placed under thefour corners of the paver(limited to 108 lb/in2 [7.6 kg/cm2]live loading)

• Preformed pavers with at leasta 3/16" (5 mm) foot in eachcorner or ribbed undersurface

• Paver pedestal of injectionmolded, weathering-grade plastic,installed under each corner(e.g., PAVE-EL by Envirospec Inc.,Terra-Tabs by Wausau Tile, etc.)

• Layer of pea gravel 1" (25 mm)(min.) free of fines

Note: This air space is not requiredif the pavers are covering only alimited area (less than 10 percentof roof area), such as corners ornarrow roof walkways.

PAVER STRAPPING ANDFASTENERS (IF REQUIRED):

Straps shall be of 22 gauge galvanized or stainless steel, 3"(75 mm) wide and 12' (3.6 m) long.

Fasteners shall be 1/4" x 1-1/4"(6 mm x 32 mm) corrosion-resistant metal anchors, expandedin pre-drilled holes (e.g., ZamacNailin #2814 by PowersFasteners, Inc).

Installation Notes

Pavers should be placed onpedestals. In colder climates, theair space will minimize anyfreeze-thaw spalling on the concrete and moisture build-upin the insulation due to vapourdrive from the inside.


CO

MP

ON

EN

TS

–

A

ll O

th

er

C

om

po

ne

nt

s

1 3

ComponentsA L L O T H E R C O M P O N E N T S

Description

MEMBRANESThe membrane is the flexible

or semi-flexible waterproofinglayer on the roof deck. In a PMRapplication, the membrane issandwiched between the roofdeck and the insulation.

Membranes fall into three general categories: built-up roof(BUR), two-ply modified bitumen,single-ply (sheet) or liquidmembranes.

Note: PMR assemblies should beinstalled with adhered membranesonly.

BUR membranes are semi-flex-ible, multi-ply roof membranes,consisting of plies or layers ofsaturated felts, coated felts, fab-rics or mats between alternatelayers of bitumen, either asphaltor coal tar based.

Modified bitumen membranesare similar to BUR membranes,but instead are manufactured ina production facility, usingasphalt modified with variousadditives. The membrane is fullyadhered and the seams overlapto provide an uninterruptedwaterproof layer.

Sheet or single-ply membranesare prefabricated sheets of polymer-based material, such as thermoplastic (e.g., PVC), elastomeric (e.g., EPDM) or modified bitumen with polymermodifiers. Single-ply roofs can be:• Fully or partially adhered: The

membrane is fully or partiallyadhered to the underlying sub-strate with a flood coat.

• Loose-laid: The membrane isnot attached to the substrateexcept at the perimeter and atpenetrations. In a PMR assem-bly, the loose-laid membraneis held in place with full ballast.(See “Ballast” on page 10 fordetails.) Care must be taken toensure that air infiltrationunderneath the membrane isprevented.

• Mechanically fastened: Themembrane is attached atdefined intervals to the sub-strate. Mechanical fasteningmay use various fasteners and/or other mechanical devices,such as plates or battens.

• Self-adhering: The membrane isadhered to a substrate and toitself at overlaps without theuse of an additional adhesive.This is usually accomplishedwith a surface adhesive pro-tected by a release paper orfilm that prevents the mem-brane from bonding to itselfduring shipping and handling.

Note: With some membranes,manufacturers may recommend aslip sheet (e.g., 4-mil polyethylenefilm) over the membrane to preventadhesion of the foam to the membrane or plasticizer migration(e.g., chemical attack) to the STYROFOAM™ Brand ExtrudedPolystyrene Foam Insulation.Consult the membrane manufac-turer for recommendations.

Liquid membranes are appliedin situ as a liquid that hardens orsets into a continuous, monolithicmembrane over the substrate.These liquids are generallyapplied by spraying or withrollers and include:• Hot-applied rubberized

asphalts, a blend of asphalt,mineral fillers, elastomers, virginor reclaimed oil. Some versionsconsist of two coats of rubber-ized asphalt with a polyestermat in between (fully reinforcedor two-ply system).

• Cold-applied liquid com-pounds consist of emulsionsand solutions of resins, elas-tomers (e.g., polyurethanes,silicones, acrylics, etc.) andbitumens and/or modifiedbitumens.

FLASHINGSFlashings are materials used

to weatherproof or seal the roofsystem edges at perimeters, penetrations, walls, expansionjoints, valleys, drains and otherplaces where the roof covering is interrupted or terminated. Forexample, membrane base flash-ing covers the edge of the fieldmembrane, and cap flashings or counterflashings shield theupper edges of the base flashing.

ROOF DECKThe roof deck (including

drains and gutters) is the struc-tural component of a building’sroof. The deck must be capableof safely supporting the designdead and live loads, includingthe weight of the roof systemsand the additional live loadsrequired by governing buildingcodes.

Decks are either non-com-bustible (e.g., corrugated metal,concrete or gypsum) or combustible (e.g., wood plank or plywood), and provide thesubstrate to which the roofingor waterproofing system isapplied.


CO

MP

ON

EN

TS

–

A

ll O

th

er

C

om

po

ne

nt

s

1 4

Function

The roof deck should:• Provide structural support to

accommodate both live anddead loads without significantdeflection.

• Provide dimensional stability byforming a stable substrate notaffected adversely by cyclicalthermal- and moisture-inducedmovement.

• Provide fire resistance as deter-mined by the building typeand intended use.

• Provide a substrate for the roofsystem.

• Accommodate building move-ment. Where necessary, buildingexpansion joints and roof areadividers should be designedand installed.

• Provide for drainage (either bysloping the roof deck or usingtapered insulation or both).The roof surface should besound and should drain waterfreely within 48 hours follow-ing a rain. Every effort shouldbe made to isolate and correctthe causes of any standingwater or ponding on the roof.CRCA recommends a minimumslope of 1/4" (6 mm) per foot(2 percent). However, if the roofis designed to allow ponding,ensure the insulation is notadhered to the membraneand a filter fabric is used.

• Provide suitable roof drainsand gutters. Care should betaken to prevent ballast fromentering the drains and/or gutters by using perforatedcollars or paving stones.When concerns exist, adrainage assessment shouldbe conducted per Sheet Metaland Air ConditioningContractors’ NationalAssociation guidelines.

The membrane should:• Provide a continuous water-

proofing barrier to protect theinterior environment.

• If the membrane is tacky, use a slip or separation sheet (e.g.,4-mil polyethylene) to mini-mize adhesion between themembrane and insulation.

• If there are compatibility issueswith the membrane, such aswith certain PVC or coal tarmembranes, refer to the manufacturer’s or supplier’srecommendations. In somecases, a slip or separation sheet(e.g., 4-mil polyethylene) maybe required.

The flashing should:• Provide a continuous water-

proofing barrier when tiedinto the membrane to protectthe interior environment.

• Extend well above the expectedhigh water level (typically 8"[200 mm] minimum).

Specification

General: The overall system(including membrane and insu-lation) should be designed so thatthe dew point is located abovethe membrane. The system shouldbe designed so that freezing willnot occur at the membrane level.

Where required, an adequatethermal barrier should be pro-vided between the insulation andthe interior of the building. Thethermal barrier may consist of thedeck, a ceiling assembly or anunderlayment board equivalentto 1/2" (13 mm) gypsum board.

Membrane: Refer to membranemanufacturer’s literature fordetails. The manufacturer orsupplier of the membrane shallbe responsible for determiningcompatibility of the membranewith STYROFOAM™ BrandExtruded Polystyrene FoamInsulation.

Roof deck and flashing: Referto general roofing specificationfor details.

Installation Notes

See the CRCA RoofingSpecification Manual. Detailsavailable at: http://www.roofingcanada.com/ItemsForSale.asp

ComponentsA L L O T H E R C O M P O N E N T S


CO

ND

IT

IO

NS

, IS

SU

ES

A

ND

R

AT

IN

GS

–

S

pe

cia

l C

on

dit

io

ns

a

nd

Is

su

es

1 5

Conditions, Issues and RatingsS P E C I A L C O N D I T I O N S A N D I S S U E S

Cold RainPhenomenon

THE ISSUE“Cold rain phenomenon” (or

“cold water wash”) occurs dur-ing periods of cold rain and/ormelting snow or when the ambi-ent condition is 33°F to 50°F(1°C to 10°C). In these conditions,the deck temperature may betemporarily reduced. The issue isthat there may be additionalheat loss, and in buildings withhigh humidity, such as pulp andpaper mills, the likelihood ofcondensation increases.

DISCUSSIONIncreased heat loss: Heat loss

studies have shown that extraheat loss in PMR systems duringperiods of “cold rain” is a tem-porary phenomenon, occurringonly during the short time ofcold rain in a heating season. Infact, cold rain in the coolingseason creates a cooling advan-tage for a PMR system. Studiescomparing a conventional versusPMR assembly show only a 3percent overall heat loss disad-vantage for the PMR assembly.

High temperature/high humiditybuildings: According to NRCA, abuilding with 45 percent RH isconsidered high moisture occu-pancy. Other buildings, such aspulp and paper mills, textilemills and natatoriums, can havean even higher internal humidity.Combining high humidity witha higher than normal operatingtemperature results in a “hightemperature/high humidity”building environment thatrequires special designconsideration.

The severe operating conditionsof high temperature/high humiditybuildings are particularly prob-lematic for conventional roofsystems. The high temperaturesdrive the high humidity upinto the roof system, resultingin severe condensation andpremature deterioration of theinsulation and roof deck.

A PMR system offers an inher-ent design solution for thismoisture problem. The water-proof roof membrane is anexcellent vapour retarder. Withthe membrane directly on theroof deck and the insulationabove the membrane, the mem-brane effectively blocks watervapour from reaching the insu-lation. Also, the membrane ismaintained at a temperaturenear that of the interior, dramat-ically reducing the probability ofcondensation on the membraneand minimizing the possibilityof premature roof failure.

The “cold rain phenomenon”can change this situation. Coldrain, filtering past the insulationto the membrane, can cool themembrane and the deck below,resulting in a temporary con-densation condition on theunderside of the deck. For somebusinesses, like pulp and papermills, this dripping condensationcan create problems with themanufacturing processes andproducts, causing decreasedproductivity and increasedproduction costs.

To solve this problem, a thinlayer of insulation can be placedbelow the membrane. This layerkeeps the roof deck warm duringbrief cold rain periods – main-taining the inherent advantagesof a PMR system while mitigat-ing the problem of the “coldrain phenomenon.”

See Blueprint 507: “STYROFOAM™

Brand Insulation in the OptimumDesign System for Pulp & PaperMill Roofs” for additional details.

CONCLUSIONThe effect of “cold rain phe-

nomenon” is temporary anddoes not have a significant over-all effect on the performance ofa PMR assembly. Generally,thicker amounts of insulationare not required to counteractthe negative effects of cold rain.

In high humidity and hightemperature applications, sand-wiching the membrane betweentwo layers of insulation, coupledwith a vapour retarder on theroof deck will address condensa-tion problems in high humidityroofing systems. Remember thatthe thicker insulation layershould be above the membraneto ensure the dew point is abovethe membrane.


CO

ND

IT

IO

NS

, IS

SU

ES

A

ND

R

AT

IN

GS

–

S

pe

cia

l C

on

dit

io

ns

a

nd

Is

su

es

1 6

MoistureAbsorption

THE ISSUESTYROFOAM™ Brand Extruded

Polystyrene Foam Insulation willabsorb water and the insulationvalue will be reduced.

DISCUSSIONIn a PMR design, it is critical

that any insulation installedabove the membrane can per-form in a wet environmentwithout any detrimental effectson its long-term performance.STYROFOAM™ Brand ExtrudedPolystyrene Foam Insulation hasa unique closed-cell structurethat provides excellent moistureresistance and long-term R-value.

Nine PMR systems were moni-tored over a period of 22 yearsand the insulation propertiesassessed. The average moisturecontent of the insulation was0.9 percent on a percent by volume basis, with a retained R-value of 96 percent.

In plaza deck designs, it isimportant that a drainage layerbe created above the insulation,allowing precipitation to drainoff the top surface of the insula-tion, creating a “diffusion open”assembly. If the insulation issandwiched between a vapourbarrier (e.g., pavers) and the roofdeck, vapour cannot escape so itis driven back into the insula-tion. To create a “diffusionopen” layer, ensure imperme-able roof coverings (such aspavers) have a ventilating airspace. This could be a layer offine-free gravel or a 3/16" (5 mm)minimum air space. See “Pavers”on page 12 for additionaldetails. In addition, if the wear-ing surface is installed in directcontact with the insulation,moisture may become trappedand freeze-thaw cycling couldcause spalling on the bottom ofthe wearing surface.

Always ensure that the roofdeck has proper drainage; if thePMR system has significantponding (e.g., standing water), theinsulation will not be “diffusionopen.” Follow roofing associationguidelines for drainage recom-mendations.

CONCLUSIONSTYROFOAM™ Brand Extruded

Polystyrene Foam Insulationoffers demonstrated long-termperformance in a PMR assembly.

DimensionalStability

THE ISSUESTYROFOAM™ Brand Extruded

Polystyrene Foam Insulation“shrinks” over time, leading toincreased heat loss.

DISCUSSIONAll building materials will

experience dimensional changedue to temperature fluctuations.STYROFOAM™ Brand ExtrudedPolystyrene Foam Insulation isno different.

For example, the coefficient of expansion of STYROFOAM™

Brand Insulation is 3.5 x 10-5

in/in/°F (6.3 x 10-2 mm/m/°C). A 2' x 4' (0.6 m x 1.2 m) sheet of insulation exposed to a tem-perature swing of 75°F (24°C)could result in a maximumchange of just 1/8" (3 mm) inthe 4' (1.2 m) direction. Oncethe temperature is reduced, theinsulation will return to its origi-nal cut dimension. In addition,this theoretical change does notaccount for the temperature profile across the insulation. For example, while one sidemay see a large temperatureswing, the underside may seeonly a small change.

This relatively small gapbetween the boards does not sig-nificantly increase the heat lossthrough the board joints. Inheat loss studies comparing PMR

versus conventional roofs, therewas no significant differencebetween the two systems. Thefindings showed that the PMRsystem used 3 percent moreenergy per year.

In addition to addressing thecoefficient of expansion, anotherconsideration is the “creep” ofmaterials. Creep is the permanentdeformation resulting from continuous, long-term dead (or non-moving) loads. Creep is generally only an issue forSTYROFOAM™ Brand Insulationused in pavements, airport run-ways, parking decks, floors, etc.– installations where the insula-tion is used to carry a significantload for a long time. In theseapplications, higher compressivestrength insulation may berequired.

CONCLUSIONAll building materials have a

coefficient of expansion thatresults in dimensional change withtemperature fluctuations. Thedimensional change that occursin STYROFOAM™ Brand Insulationin a PMR assembly does not sig-nificantly impact the system’sthermal performance.



CO

ND

IT

IO

NS

, IS

SU

ES

A

ND

R

AT

IN

GS

–

S

pe

cia

l C

on

dit

io

ns

a

nd

Is

su

es

1 7

Vegetative RoofDesign

THE ISSUECan PMR assemblies be used

for vegetative roof designs?

DISCUSSIONIn a “green roof” design, the

ballast in a PMR assembly isessentially replaced with vegeta-tive soil and plantings – plus adrainage layer directly on top ofthe insulation (Figure 6).Replacing conventional ballastwith vegetation can limit stormwater runoff and, by filteringthe runoff through the plants,also improve the quality of therunoff. The plantings not onlyballast the insulation, they can,depending on the configura-tion, also add additional R-value (RSI) to the roof assembly.Vegetative roofs provide habitatfor insects and other wildlifeand often are considered inbuildings applying for USGBC orCAGBC Leadership in Energyand Environmental Design(LEED††) certification.

Many materials may be suitableas ballast, provided they arecompatible with the insulation,prevent flotation, shield ultra-violet light and provide a ClassA fire-resistant roof finish.

The roof structure must also bedesigned to accommodate thedead load from the additionalweight of the plantings (includingwhen they are fully saturated byrainfall and covered in severalfeet of snow), plus any live loadfrom traffic, if applicable. It isalso important to design theroof slope and drainage systemto accommodate rain runoff.

Figure 6: Vegetative Roof Design

PMR assemblies are ideal forvegetative roof designs:• The membrane is protected

under the insulation. • Because STYROFOAM™ Brand

Extruded Polystyrene FoamInsulation comes in a range ofcompressive strengths, theinsulation layer can bedesigned to withstand thehigher dead loads.

• STYROFOAM™ Brand Insulationis proven to outperform in amoist environment.

• STYROFOAM™ Brand Insulationhas a high modulus of elasticity,allowing it to perform underlong-term live or cycle loading.Maximum recommendeddynamic (live) load is 1/10 ofthe rated compressive strengthfor 1,000,000 repetitions toaddress creep and fatigueguidelines.

Typically, a drainage layer isplaced over the insulation todirect runoff to the drains, aswell as keep the top surface ofthe insulation “diffusion open.”(See “Moisture Absorption” onpage 16 for details.) Thisdrainage layer usually includes afabric over the insulation to pro-tect the joints and keep themopen for drainage. Any stoneused for this drainage layer mustbe clean and have a low per-centage of fines. In some cases,a drainage mat combined with afilter fabric has also been usedsuccessfully to create the neces-sary air space.

For additional information onvegetative roof design, see:

Design Guidelines for Green Roofs,by Steven Peck and MonicaKuhn, B.E.S., B. Arch., OAA, anOAA and CMHC publication,available at http://www.cmhc-schl.gc.ca

CONCLUSIONPMR assemblies are ideally

suited to vegetative roof designs.

Vegetation

Soil

System Filters

Filter Fabric

STYROFOAM™ Brand Foam Insulation

Membrane

Deck

††The U.S. Green Building Council (USGBC), a nonprofit coalition promoting high-

performance green building design, has developed Leadership in Energy and

Environmental Design (LEED), a voluntary, consensus-based standard. The LEED

rating recognizes the life cycle costing of construction. The Canada Council

(CAGBC) LEED rating system is modeled after the USGBC LEED program.



CO

ND

IT

IO

NS

, IS

SU

ES

A

ND

R

AT

IN

GS

–

S

pe

cia

l C

on

dit

io

ns

a

nd

Is

su

es

1 8

Finding Leaks in a PMR

THE ISSUEIs it more difficult to locate a

leak with a PMR or conventionalroof assembly?

DISCUSSIONBuilding upon years of in-field

experience, the majority of roofleaks in PMR systems occur atflashing as opposed to the inte-rior field area. The field area isprotected from physical abuse,UV attack and thermal cycling –all factors that are the primarycauses of roof failures – by boththe insulation and ballast overthe membrane. However, some-times interior field leaks dooccur.

Concrete decks: For PMRinstallations on concrete decks,generally the membrane is fullyadhered to the deck. This simpli-fies leak detection because theleak is localized. For example,the leak in the interior will beexactly where the hole in themembrane is located. If themembrane is not adhered, thewater can run under the mem-brane for many feet beforeentering the building – just likein a conventional roof.

Steel decks: For PMR installa-tions on steel decks, a layer ofinsulation or other substrate(e.g., drywall) is placed first toprovide a base for the mem-brane – exactly the same as in aconventional roof. The sametype of leak detection effort isrequired for both PMR and con-ventional roofs on steel decks.

Wood decks: On wood deckswith a PMR installation, themembrane is typically a feltlayer and two or three pliesmopped on top. In a conven-tional installation, the insulationis fastened to the deck and thenthe membrane is applied. Bothof these approaches will allowthe water to run to the deckjoints prior to entering thebuilding.

CONCLUSIONNot only do PMR assemblies

have fewer leaks in the firstplace, PMR assemblies overconcrete decks with bondedmembranes have definite advan-tages when isolating any leaksthat do occur. Both conventionaland PMR roofs over steel orwood decks require the sameleak detection strategies. Inaddition, because PMR roofs areeasier to repair and typically allof the original materials can bereused (ballast and insulation),this environmentally friendlyfeature can save money.

Low TemperatureApplications

THE ISSUEPMR assemblies should

not be used in low temperatureapplications because of thepotential adverse effect on theSTYROFOAM™ Brand ExtrudedPolystyrene Foam Insulation.

DISCUSSIONIn a low temperature applica-

tion (e.g., freezers), the interiorspace has a low temperature andlow water vapour pressure(humidity). In contrast, thewarm outside temperature andhigher water vapour pressurecauses a vapour drive toward theinterior space. Unless addressed,this vapour can condense in theinsulation and lower the R-value(RSI) of the system. It can alsocondense on the membrane andfreeze, gradually forming a layerof thick ice.

Typically in low temperatureapplications, the membrane isplaced on the “warm side” – orthe exterior in a conventionalroofing application.

CONCLUSIONIn low temperature applications

(e.g., freezers), a conventionalroof may offer performancebenefits.


CO

ND

IT

IO

NS

, IS

SU

ES

A

ND

R

AT

IN

GS

–

S

pe

cia

l C

on

dit

io

ns

a

nd

Is

su

es

1 9

High TemperatureInstallation

THE ISSUEIn high temperature locations,

PMR assemblies should not be covered with a dark fabricprior to laying the ballastbecause of the potential adverseeffect on the STYROFOAM™

Brand Extruded PolystyreneFoam Insulation.

DISCUSSIONLike many insulations, higher

temperatures may cause permanentdistortion and/or long-termcreep. The maximum usetemperature for STYROFOAM™

Brand Extruded PolystyreneFoam Insulation is 165°F (74°C)for continuous use, with short-term exposure up to 190°F(88°C).

Typically, this concern arisesin warmer locations (e.g., south-ern U.S.) when STYROFOAM™

Brand Insulation is placed under-neath a dark fabric prior to lay-ing the ballast. Given the rightconditions, the temperature onthe top of the insulation mayreach close to the upper limitsfor polystyrene insulation andcause some distortion. Experiencehas shown that when STYROFOAM™

Brand Insulation is exposed toboth direct sunlight and an out-door air temperature over 90°F(30°C), distortion can occur inas little as 30 minutes when adark fabric is installed over the insulation. To prevent this phe-nomenon during hot weather,temporarily place white opaquepolyethylene film on the insula-tion until the ballast is laid (oruse a white filter fabric).

In addition, reflective surfacessuch as glass or metal wall panelscan substantially increase surfacetemperatures. When combinedwith a dark fabric, extremelyhigh surface temperatures canoccur, increasing the potentialfor distortion of rigid foamboards. Follow the same precau-tion as mentioned above.

CONCLUSIONIn high temperature locations,

the temporary use of whiteopaque polyethylene film laidon the insulation until the ballast is laid will prevent anydistortion of the insulation (oruse a white filter fabric).

Membrane SeamFailure

THE ISSUEFailures at the seams in

thermoset membranes may be worse with PMR because the membrane stays damp.

DISCUSSIONThermoset membranes (such

as EPDM and neoprene) werehistorically seamed with a con-tact adhesive. Seam failure dueto moisture intrusion or othercontaminant was a concern forthis type of membrane becausethe membrane stays damp in aPMR, potentially resulting in anincrease in seam failure. In fact,Dow never received a complaintabout this perceived concern.

In today’s EPDM system, aseam tape is used. This tape hasexhibited excellent performanceand this is no longer an issue.

CONCLUSIONThere are no documented

cases of seam failure related tothe PMR application.

Plant Growth onPMR Assemblies

THE ISSUEPeriodically, plant growth

will occur on PMR and otherlow-sloped roofs. Can this beavoided?

DISCUSSIONAt times, grass, weeds or small

trees may grow on both PMRand conventional roofs. Goodroofing practice should includea maintenance program thatincludes periodic inspection forthis type of growth. Any plantgrowth should be pulled outand, if required, the area treatedwith a weed killer.

Roots from plant growth cansometimes damage the mem-brane if left unchecked. With aPMR system, there is less chanceof this happening since themembrane is protected by theinsulation, fabric and ballast.

CONCLUSIONA preventive maintenance and

inspection program shouldinclude inspection and removalof any plant growth.



CO

ND

IT

IO

NS

, IS

SU

ES

A

ND

R

AT

IN

GS

–

F

ir

e a

nd

W

in

d R

at

in

gs

2 0

Overview

Fire and wind ratings arerequired to meet building coderequirements. Typically, a PMRassembly, including roof deck,membrane, insulation and ballast, is tested in exactly thesame configuration as would be constructed in the field. Nodeviation from the componentspecification is allowed.

Underwriters Laboratories Inc.(ULI), Underwriters LaboratoriesCanada (ULC) and FactoryMutual (FM) have developed testmethods to rate the fire andwind properties of assemblies.

For the most current listings,contact Dow at 1-866-583-BLUE(2583).

Test Methods

FIRE RESISTANCE RATINGS –FIRE WITHIN A BUILDING

Both ULI and ULC test roofassemblies based on the type offire exposure. For fires originatingwithin a building, roof assembliesare assessed using either ANSI/UL263 or CAN/ULC S101-M.

When testing for fires originat-ing within a building, a full-scaleroof system is exposed to a controlled fire in order to assessa construction/assembly that can contain a fully developedfire. The Fire Resistance Ratingrepresents the time it takes forthe temperature on the unex-posed side of the assembly toincrease by 250°F (121°C).

A sample measuring approxi-mately 14' x 17' (4.3 m x 5.2 m)is used, including the deckingmaterial, any suspended ceiling,hangers, insulation, etc. Thesample is then exposed to a firewith temperatures reaching 1,000°F(537°C) at five minutes and then1,700°F (927°C) for a specifiedtime. During the test, a load isapplied to the floor to representthe maximum load the joists aredesigned to support.

EXTERNAL FIREPERFORMANCE OF A ROOF ASSEMBLY

The fire resistance performanceof roof coverings exposed tosimulated fire source originatingoutside a building is conductedin accordance with ULI 790(ASTM E108) or CAN/ULC S107-M.Three classifications are available.

Class A roof covering:• Effective against severe fire test

exposures• Provides a high degree of fire

protection• Not expected to produce flying

embers• Does not slip from position

during the test

Class B roof covering:• Effective against moderate fire

test exposures• Provides a moderate degree of

fire protection• Not expected to produce flying


during the test

Class C roof covering:• Effective against light fire test

exposures• Provides a light degree of fire

protection• Not expected to produce flying


during the test

Note: PMR assemblies ballastedwith a minimum of 9 lb/ft2 (44kg/m2) of stone ballast (or paversinstalled with a maximum gap of1/4" [6 mm]) achieve a Class Arating.

FM TESTS FOR WIND PERFORMANCE

Factory Mutual approved roofassemblies are only required whenthe building is insured by FMGlobal. Building code authoritiesmay recognize some FM standards; however, they do notrequire the use of FM approvedor accepted products and systems.

FM 4450, “Approval Standardfor Class 1 Insulated Steel DeckRoofs,” and FM 4470, “ApprovalStandard for Class 1 RoofCovers,” are two recognized laboratory test methods fordetermining the wind-upliftresistances of roof assemblies.FM 4450 and FM 4470 are thebasis of FM’s 1-60, 1-90, 1-120,etc., approvals. For example, aClass 1-60 design resists a 60lb/ft2 (2.88 kPa) uplift pressurefor one minute without loss ofpressure.

Dow has a PMR system ratedFM 1-90 that adheres STYROFOAM™ Brand ExtrudedPolystyrene Foam Insulation toa BUR assembly with asphalt.This system can be used on bothsteel and concrete roof decks.Loose-laid single-ply roof mem-branes with ballast are not listedin the FM approval guide sincethere are not methods to testthese systems for wind uplift.Loose-laid systems can be“accepted” by FM if the assem-bly is ballasted in accordancewith FM Loss Prevention Guide1-29 and reviewed by the localFM engineering office.

REQUIREMENTS FORBALLASTED ROOFASSEMBLIES

PMR assemblies should beballasted according to therequirements listed in “Ballast”on page 11.


Conditions, Issues and RatingsF I R E A N D W I N D R A T I N G S

CO

ND

IT

IO

NS

, IS

SU

ES

A

ND

R

AT

IN

GS

–

F

ir

e a

nd

W

in

d R

at

in

gs

2 1

ULI Hourly Fire Resistance Ratings for PMR – Steel Deck

Note: Always refer to the actual listing for complete details, including maximum thickness of insulation allowed. For details, call Dow at 1-866-583-BLUE (2583).

Assembly #

P-225, P-226, P-235(New PMR)

P-404(New PMR)

P-801, P-805(Retrofit PMR)

P-803(Retrofit PMR)

P-811(New PMR)

P-813(New PMR)

P-908

Rating (hrs)

1, 1-1/2

1-1/2

1, 1-1/2, 2

1, 1-1/2

1, 1-1/2, 2, 3

1, 1-1/2

2

Description

Steel deck1/2" or 5/8" (13 mm or 16 mm) Type X gypsum (varies)Bar joists Suspended ceiling

Steel deck1" (25 mm) mineral or fiberboardBar joistsPlaster ceiling

Steel deckMineral or fiberboardsSpray fiber fireproofingBeam construction

Steel deckMineral or fiberboardsSpray fiber fireproofingBar joists

Steel deck5/8" (16 mm) Type X gypsumSpray fiber fireproofingBeam constructionSuspended ceiling (optional)

Steel deck5/8" (16 mm) Type X gypsum Spray fiber fireproofingBar joists

Steel deck3-5/6" (97 mm) vermiculite concreteBeam construction


CO

ND

IT

IO

NS

, IS

SU

ES

A

ND

R

AT

IN

GS

–

F

ir

e a

nd

W

in

d R

at

in

gs

2 2

ULI Hourly FireResistance Ratings forPMR – Concrete Deck

Assembly #

P-904, P-909, P-912, P-915(Retrofit PMR)

P-904, P-909, P-912, P-915(New PMR)

Rating (hrs)

2

2

Description

Precast concrete units Mineral fiberboard

Precast concrete units1" (25 mm) gypsum board

ULI Hourly FireResistance Ratings forPMR – Other

Assembly #

P-229, P-505, P-507(New PMR)

Rating (hrs)

1, 1-1/2

Description

2" (50 mm) poured gypsum deckBar joistsSuspended ceiling


§StrataGuard is a trademark of Owens Corning§§DensDeck is a trademark of Georgia-Pacific

CO

ND

IT

IO

NS

, IS

SU

ES

A

ND

R

AT

IN

GS

–

F

ir

e a

nd

W

in

d R

at

in

gs

2 3

ULC Hourly Fire Resistance Ratings for PMR –Metal Deck

Assembly #

R-202, R-217 (New PMR)

R-702, R-703 (New PMR)

R-804 (New PMR)

R-805, R-806 (New PMR)

Rating (hrs)

1

1, 1-1/2

3/4, 1, 1-1/2,2, 3

1

Description

Steel deck1/2" (13 mm) gypsumBeams or bar joistsSuspended ceiling

Steel deck5/8" (16 mm) gypsumSpray cementitious mixtureBeams or bar joists

Steel deck5/8" (16 mm) Type X gypsumSpray fiber fireproofingBeam construction

Steel deck1/2" or 5/8" (13 mm or 16 mm) Type X gypsum (varies)Spray fiber fireproofingBeams or bar joists


Assembly #

P-229, P-505, P-507 (New PMR)

ULC Hourly Fire Resistance Ratings for PMR –Concrete Deck

Rating (hrs)

1, 1-1/2

Description

2" (50 mm) poured gypsum deckBar joistsSuspended ceiling

FM Hourly Fire Resistance Ratings for PMR

FM Class 1 Fire and Wind Uplift

Note: Current FM wind tests cannot be used to evaluate loose-appliedroofing systems. FM Loss Prevention Guide 1-29 provides accepted ballasting requirements.

Assembly #

RC-227 (New PMR)

RC-264 (New PMR)

Rating (hrs)

1

1

Description

Steel deck1/2" (13 mm) Type X gypsumGypsum board ceiling

Steel deck1/2" (13 mm) Type X gypsumSuspended ceiling

Class

1-60, 1-90

Description

Steel deck1/2" (13 mm) StrataGuard§ or 5/8" (16 mm)DensDeck§§

(mechanically fastened)3-ply BUR

Printed in U.S.A. ®™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow

Illustrations are not intended to replace the need for design by appropriate professionals such as architects or engineers.

NOTICE: No freedom from any patent owned by Dow or others is to be inferred. Because use conditions and applicable laws may differ from one location to another and may change with time, Customer is responsible for determiningwhether products and the information in this document are appropriate for Customer’s use and for ensuring that Customer’s workplace and disposal practices are in compliance with applicable laws and other government enactments.Dow assumes no obligation or liability for the information in this document. NO EXPRESS WARRANTIES ARE GIVEN EXCEPT FOR ANY APPLICABLE WRITTEN WARRANTIES SPECIFICALLY PROVIDED BY DOW. ALL IMPLIED WARRANTIES INCLUDING THOSE OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE EXPRESSLY EXCLUDED.

STYROFOAM™ Brand Extruded Polystyrene Foam InsulationCAUTION: This product is combustible. Protect from high heat sources. A protective barrier or thermal barrier may be required as specified in the appropriate building code. For more information, consult MSDS, call Dow at 1-866-583-BLUE (2583) or contact your local building inspector. In an emergency, call 1-519-339-3711.

WARNING: Rigid foam insulation does not constitute a working walkable surface or qualify as a fall protection product.

Building and/or construction practices unrelated to building materials could greatly affect moisture and the potential for mould formation. No material supplier including Dow can give assurance that mould will not develop in any specific system.

Form No. 178-00554X-1109P&M

For Technical Information: 1-866-583-BLUE (2583) (English) . 1-800-363-6210 (French)

For Sales Information: 1-800-232-2436 (English) . 1-800-565-1255 (French)

DOW CHEMICAL CANADA ULC . Dow Building Solutions . Suite 2100 . 450 – 1st St., SW . Calgary, AB T2P 5H1

www.dowpmr.com

For information on how Dow Building Solutions is helping

reduce the carbon footprint at the 2010 Winter Olympic

Games and beyond, visit www.dow.com/2010

canada commercial protected membrane roof installation ......protected membrane roof installation...

Documents