United States COMMERCIAL Protected Membrane Roof ...ecatalog.bc.com/.../SiteContent/1/pdfs/Protected_Membrane_Roof_Installation_Guidelines.pdfProtected Membrane Roof Installation Guidelines

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

United States C O M M E R C I A L

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


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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 Foam (XPS)Insulation, 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


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

Advantages of PMRAll flat roof assemblies consist

of 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 performanceand 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 and re-installation of the ballast andinsulation for making repairsor for constructing additionalstories. In addition, a protectedmembrane roof provides anenvironmentally preferredoption to reuse the insulation

• Allow for a range of ballastoptions – stone, precast pavingslabs, soil and plantings for avegetative roof, interlockingstone or concrete – depending onuse and aesthetic considerations

• Are compatible with a range of membrane types

• Eliminate the need for a separate vapor 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-resistantqualities, STYROFOAM™ BrandExtruded Polystyrene FoamInsulation delivers exceptionalperformance in roofing andplaza applications.• Provides excellent moisture

resistance and long-termR-value*

• 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, 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 vapor 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, state,county or city agencies, or inowners’ specifications to be used in the design of a building.

Dew Point: the temperaturewhere water vapor condenses in cooling air at the existingatmospheric pressure and vapor 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.

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Glossary


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Glossary

Humidity: the amount of moisture contained in theatmosphere. Generally expressedas percent relative humidity (% RH). It is the ratio of theamount of water vapor 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, vaporretarder [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 of roof area.

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

Vapor Retarder: a material thatrestricts the movement of watervapor.

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.

DescriptionSTYROFOAM™ Brand Extruded

Polystyrene (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 vapor, providing demon-strated long-term mechanicaland thermal performance.

The boards are available in arange of thicknesses, densities,and edge and surface treatments.


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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. Idealfor installation above waterproofing orroofing membranes in PMR applications.

STYROFOAM™ Brand Ribbed ROOFMATE™

An extruded polystyrene foam insulationboard with 1/4" x 1/2" drainage channelson the bottom long edge of each board.The top surface of the board has ribs thatform corrugations in the long dimensionof the board.

Designed for installation above water-proofing or roofing membranes in PMRapplications that use pavers as ballast.Pavers can be installed directly over theribbed foam surface without needingpedestals.

STYROFOAM™ Brand PLAZAMATE™

A high-density extruded polystyrene foaminsulation board designed to be installedabove waterproofing or roofing membranesin most plaza deck 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.


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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

FunctionProvide thermal properties:

STYROFOAM™ Brand ExtrudedPolystyrene Foam Insulation hasa high aged thermal resistance(R-value) when compared withcompetitive 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.

SpecificationThe insulation shall meet

ASTM C578-05 (Type V, VI orVII depending on the requiredproperties) or CAN/ULC S701Type 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" gapbetween boards, staggering endjoints. The recommended staggerbetween each board is 2'.However, in cases where boardshave been cut to fit, maximizethe stagger where possible. At aminimum, each board shouldhave at least an 8" stagger.

When using STYROFOAM™

Brand Insulation with pre-cutdrainage channels, ensure thatthe drainage channel edges areface down (i.e., on the membraneside).

Bevel edges to fit closely tocant slopes.

Fit around protrusions andobstructions with a maximum3/4" gap to minimize heat loss.

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

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

• The bottom layer must be thethickest or, at minimum, equalto the top layer (e.g., 3" bottomand 3" top).

• Lay successive layers of insulation unbonded or unadhered.

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

Installation NotesProtect insulation from physi-

cal damage.Handle boards carefully to pre-

vent damage during installation.Always wear protective eyewear

and gloves when handling andcutting insulation.

Always store insulation awayfrom direct sunlight, particularlywhen storing for an extendedtime. Cover with a light-coloredopaque 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.

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ComponentsF A B R I C

DescriptionBallast 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 penetrating

between insulation boards• Raft the insulation together

to reduce ballast requirements• Reduce mechanical damage

to insulation• Allow easy stone removal if

access is required to flashings,insulation and/or membrane

Overlap all edges a minimumof 12". If a small piece has to beused, minimum size should be 8' x 8'.

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

SpecificationApply fabric unbonded and

shingle fashion over the installedinsulation (Figure 3).

Ballast

Filter Fabric


Membrane

Deck

STYROFOAM™Brand FoamInsulation

BallastFilter 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-coloredproducts, such as black plasticdrainage boards (dimpleboards) or dark fabric, are notplaced over the insulationand then left exposed. Dark-colored 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.


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ComponentsF A B R I C

Installation NotesStore 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, distor-tion of the foam can occur in aslittle as 30 minutes when a heavy,dark-colored fabric is over theinsulation. To prevent this phe-nomenon during hot weather,temporarily place white opaquepolyethylene film on the fabricuntil the ballast is laid (or use awhite filter fabric).

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

SupportingDocumentation

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

Extend the fabric up the roof perimeter cants and roofprotrusions by at least 3" abovethe top level of the ballast (typically about a 6" upturn) and place it loose under themetal 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 UpliftAround 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 ValueUnit 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


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DescriptionCrushed stone or washed,

rounded riverbed rock, ASTMD448 Gradation #2, 4, 5 or 57depending on membrane type,building height, wind zone andparapet height (Table 2).

Depending on the ballastdesign, the range of ballast is 10 to 15 lb/ft2 with additionalballast around perimeters andpenetrations (15 to 20 lb/ft2). In some cases, pavers can beused. See “Pavers” on page 12 for additional details.

FunctionPrevent uplift and prevent

flotation: The amount andplacement of ballast is based onthe following considerations:• Design wind speed – Refer to

the ANSI/ASCE 7-95 windspeed map, contact the localcode authority for the designwind speed for the buildinglocation or refer to TechSolutions 508.1: “Ballast DesignGuide for PMR Systems (U.S.)”

• Roof height – Use the worst-case elevation (e.g., fromground level to the highestpoint of the roof)

• Parapet height – Measuredfrom the top of the ballast tothe top of the parapet, use theshortest parapet height in anyvariation

• Membrane type – Adhered,loose-laid or mechanicallyattached

Areas of extra ballasting:Extra ballast, required to overcomehigh wind loads and restraininsulation during heavy rain-storms, should be considered inthe following locations:• Perimeter edge – 8.5' wide

band running along theperimeter edge of the roofinsulation. As an alternate to additional ballast, 1 to 4 rowsof concrete pavers may beinstalled along the perimeteredge (see Tech Solutions 508.1).

• Penetrations through the insu-lation – 4' wide band aroundany roof penetration greaterthan 4' in any direction (e.g.,skylights, equipment pads, etc.).

• Corners – Concrete pavers maybe required with steel strappingand anchors for certain designs(see Tech Solutions 508.1). See“Pavers” on page 12 for detailsabout concrete pavers.

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

• Membrane type – Adhered,mechanically fastened or fullyballasted. For additionaldetails, see “All OtherComponents” on page 13.

Prevent wind scouring: Thewind performance of stone- ballasted PMR assemblies has beenexcellent. In these instances, con-crete pavers should be considered.Only a few isolated minor scouringproblems have occurred, typicallylimited to small areas in andaround corners. In these fewcases, the ballast has blowninbound by about 4' and piledup on the filter fabric, creatingadditional weight. See “Pavers”on page 12 for details.

Prevent UV degradation ofthe insulation: Most PMR applications use a filter fabricthat typically incorporates a UVstabilizer. However, if no fabricis used, the insulation must betotally covered by the ballast toprevent UV degradation. Thequality of the ballast is critical inthese types of applications. Toosmall (fines not more than 10percent of mix) and the stonesmay work into the insulationjoints or be moved by the wind;too large and the ballast may notprovide adequate cover to protectfrom UV light.

Provide a Class A fire-resistantroof cover: Class A roof covering,as defined by ULC S107, ULI790 and ASTM E108. (See “Fireand Wind 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 or pavers providethe Class A fire rating.

Standard Sizes of Coarse Aggregate (Weight % Finer Than Sieve Openings)

ASTM D448 Nominal Size 3" 2-1/2" 2" 1-1/2" 1" 3/4" 1/2" 3/8" 3/16"Gradation Square Openings2 2-1/2" to 1-1/2" 100% 90-100% 35-70% 0-15% 0-5%

4 1-1/2" to 3/4" 100% 90-100% 20-55% 0-15% 0-5%

5 1" to 1/2" 100% 90-100% 20-55% 0-10% 0-5%

57 1" to No. 4 100% 95-100% 25-60% 0-10%

T A B L E 2

ComponentsB A L L A S T

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ComponentsB A L L A S T

Design ApproachRefer to Tech Solutions 508.1

for the recommended amountand placement of ballast. Theballast design depends on:• Type of membrane (adhered,

loose-laid or mechanicallyattached)

• Building height• Design wind speed• Site exposure• Parapet height• Gravel stop height

SpecificationASTM D448 Gradation #2, 4, 5

or 57 washed free of fines orstones.

Spread stone ballast uniformlyover installed insulation to provide minimum weight orthickness.

Spread additional ballastaround the roof perimeter for a width of 8.5' to increase ballastweight or thickness.

Spread additional ballastaround any penetration for a width of 4' around any pene-tration that exceeds 4' in anydirection.

Installation NotesMake 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 and bil-lowing it.

For PMR installations withouta fabric, ensure that the ballastdoes not contain too many smallstones (fines not more than 10percent of mix) as they maywork into the insulation joints orbe 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, the height of the gravel stop at a building perimeter should beat least 2" from the top of theballast.

SupportingDocumentation

Tech Solutions 508.1: “BallastDesign Guide for PMR Systems(U.S.)”

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

ANSI/SPRI RP-4 Wind DesignStandard for Ballasted Single-PlyRoofing Systems (for mechanicallyattached and loose-laid PMR)

ASTM D448 StandardClassification for Sizes ofAggregate for Road and BridgeConstruction

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

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ComponentsP A V E R S

DescriptionConcrete 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.

FunctionNote: 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.

SpecificationPAVERS

Concrete pavers shall be man-ufactured from minimum 3,000lb/in2 concrete with a minimumweight of 18 lb/ft2.

When ribbed insulation is notused and the total area to becovered by pavers is more than10 percent and the location hasmore than 3,000 heating degree-days, pavers should be raisedfrom the surface of the fabricand insulation using spacersto maintain at least a 3/16"ventilating air space (“diffusionopen” design). The pedestal can be:• 1" thick insulation cut into

6" square blocks and placedunder the four corners of thepaver (limited to 108 lb/in2

live loading)• Preformed pavers with at least

a 3/16" foot in each corner orribbed 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" (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" wide and 12' long.

Fasteners shall be 1/4" x 1-1/4"corrosion-resistant metalanchors, expanded in pre-drilledholes (e.g., Zamac Nailin #2814by Powers Fasteners, Inc).

Installation NotesWhen pavers cover more than

10 percent of the insulation sur-face and are located in climateswith more than 3,000 heatingdegree-days, create a 3/16" spacebetween the insulation and the underside of the pavers. In colder climates, the air spacewill minimize any freeze-thawspalling on the concrete andmoisture build-up in the insula-tion due to vapor drive from theinside.


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

DescriptionMEMBRANES

The membrane is the flexibleor 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 withpolymer modifiers. Single-plyroofs 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 compoundsconsist of emulsions and solu-tions of resins, elastomers(e.g., polyurethanes, silicones,acrylics, etc.) and bitumensand/or modified bitumens.

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-combustible(e.g., corrugated metal, concrete orgypsum) or combustible (e.g., woodplank or plywood), and provide thesubstrate to which the roofing orwaterproofing system is applied.


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FunctionThe 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 and NRCA recommenda minimum slope of 1/4" perfoot (2 percent). TheInternational Building Code(IBC) also requires a slope of1/4", except for coal tar mem-branes that require 1/8" slope.However, if the roof isdesigned to allow ponding,ensure the insulation is notadhered to the membrane and 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 SheetMetal and 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"minimum).

SpecificationGeneral: 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" gypsum board.

Membrane: Refer to membranemanufacturer’s literature for details.The manufacturer or supplier ofthe membrane shall be responsiblefor determining compatibility ofthe membrane with STYROFOAM™

Brand Extruded Polystyrene FoamInsulation.

Roof deck and flashing: Referto general roofing specificationfor details.

Installation NotesSee the NRCA Roofing and

Waterproofing Manual – FifthEdition. Online edition availableat: http://www.nrca.net/rp/technical/manual/manual.aspx

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


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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. In these conditions, the decktemperature may be temporarilyreduced. The issue is that theremay be additional heat loss, andin buildings with high humidity,such as pulp and paper mills,the likelihood of condensationincreases.

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 vapor retarder. Withthe membrane directly on theroof deck and the insulationabove the membrane, the mem-brane effectively blocks watervapor from reaching the insula-tion. 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 TechNote 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 vapor 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.


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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 vaporbarrier (e.g., pavers) and the roofdeck, vapor cannot escape so itis driven back into the insulation.To create a “diffusion open”layer, ensure impermeable roofcoverings (such as pavers) havea ventilating air space. Thiscould be a layer of fine-freegravel or a 3/16" minimum airspace. See “Pavers” on page 12for additional details. In addi-tion, if the wearing surface isinstalled in direct contact withthe insulation, moisture maybecome trapped and freeze-thawcycling could cause spalling onthe bottom of the wearingsurface.

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 ofexpansion of STYROFOAM™

Brand Insulation is 3.5 x 10-5

in/in/°F. A 2' x 8' sheet of insula-tion exposed to a temperatureswing of 75°F could result in amaximum change of just 1/4" inthe 8' direction. Once the tem-perature is reduced, the insulationwill return to its original cutdimension. In addition, this theoretical change does notaccount for the temperature pro-file across the insulation. Forexample, while one side may seea large temperature swing, theunderside may see only a smallchange.

This relatively small gapbetween the boards does not sig-nificantly increase the heat lossthrough the board joints. Inheat loss studies comparing PMRversus conventional roofs, therewas no significant difference

between 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 changewith temperature fluctuations.The dimensional change thatoccurs in STYROFOAM™ BrandInsulation in a PMR assemblydoes not significantly impact thesystem’s thermal performance.



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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 vegetativesoil and plantings – plus a drainagelayer directly on top of theinsulation (Figure 6). Replacingconventional ballast with vege-tation can limit storm waterrunoff and, by filtering therunoff through the plants, alsoimprove the quality of therunoff. The plantings not onlyballast the insulation, they can,depending on the configuration,also add additional R-value tothe roof assembly. Vegetativeroofs provide habitat for insectsand other wildlife and often areconsidered in buildings applyingfor USGBC 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 toprotect the joints and keepthem open for drainage. Anystone used for this drainagelayer must be clean and have alow percentage of fines. In somecases, a drainage mat combinedwith a filter fabric has also beenused successfully to create thenecessary 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 greenbuilding 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.


††


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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 application

(e.g., freezers), the interior spacehas a low temperature and lowwater vapor pressure (humidity).In contrast, the warm outsidetemperature and higher watervapor pressure causes a vapordrive toward the interior space.Unless addressed, this vapor cancondense in the insulation andlower the R-value of the system.It can also condense on themembrane and freeze, graduallyforming a layer of 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.


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High TemperatureInstallation

THE ISSUEIn high temperature locations,

PMR assemblies should not becovered with a dark fabric priorto laying the ballast because ofthe potential adverse effect onthe STYROFOAM™ Brand ExtrudedPolystyrene Foam Insulation.

DISCUSSIONLike many insulations, higher

temperatures may cause permanentdistortion and/or long-term creep.The maximum use temperaturefor STYROFOAM™ Brand ExtrudedPolystyrene Foam Insulation is165°F for continuous use, withshort-term exposure up to 190°F.

Typically, this concern arisesin warmer locations (e.g., southernU.S.) when STYROFOAM™ BrandInsulation is placed underneatha dark fabric prior to laying theballast. Given the right condi-tions, the temperature on thetop of the insulation may reachclose to the upper limits forpolystyrene foam insulation andcause some distortion.Experience has shown that whenSTYROFOAM™ Brand Insulation isexposed to both direct sunlightand an outdoor air temperatureover 90°F, distortion can occurin as little as 30 minutes whena dark fabric is installed over theinsulation. 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, extremely highsurface temperatures can occur,increasing the potential for distortion of rigid foam boards.Follow the same precaution asmentioned above.

CONCLUSIONIn high temperature locations,

the temporary use of whiteopaque polyethylene film laidon the insulation until the ballastis laid will prevent any distortionof the insulation (or use a whitefilter 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.



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OverviewFire and wind ratings are

required 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 MethodsFIRE 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.

A sample measuring approxi-mately 14' x 17' is used,including the decking material,any suspended ceiling, hangers,insulation, etc. The sample isthen exposed to a fire withtemperatures reaching 1,000°Fat five minutes and then 1,700°Ffor a specified time. During thetest, a load is applied to the floorto represent the maximum loadthe joists are designed 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 UL 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 ofstone ballast (or pavers installedwith a maximum gap of 1/4")achieve a Class A rating.

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 uplift pressure for oneminute without loss of pressure.

Dow has a PMR system ratedFM 1-90 that adheres STYROFOAM™ Brand ExtrudedPolystyrene Foam Insulation toa BUR roof assembly withasphalt. This system can be usedon both steel and concrete roofdecks. Loose-laid single-ply roofmembranes with ballast are notlisted in the FM approval guidesince there are not methods totest these systems for winduplift. 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.

IBC REQUIREMENTS FOR BALLASTED ROOFASSEMBLIES

The International BuildingCode (IBC) requires that ballastedroofing assemblies, includingPMR assemblies, be ballasted inaccordance with ANSI/SPRI RP-4.This standard can be down-loaded (free of charge) atwww.spri.org


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

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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" Type X gypsum (varies)Bar joists Suspended ceiling

Steel deck1" mineral or fiberboardBar joistsPlaster ceiling

Steel deckMineral or fiberboardsSpray fiber fireproofingBeam construction

Steel deckMineral or fiberboardsSpray fiber fireproofingBar joists

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

Steel deck5/8" Type X gypsum Spray fiber fireproofingBar joists

Steel deck3-5/6" vermiculite concreteBeam construction


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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" 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" poured gypsum deckBar joistsSuspended ceiling


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

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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" gypsumBeams or bar joistsSuspended ceiling

Steel deck5/8" gypsumSpray cementitious mixtureBeams or bar joists

Steel deck5/8" Type X gypsumSpray fiber fireproofingBeam construction

Steel deck1/2" or 5/8" 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" 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" Type X gypsumGypsum board ceiling

Steel deck1/2" Type X gypsumSuspended ceiling

Class

1-60, 1-90

Description

Steel deck1/2" StrataGuard§ or 5/8" DensDeck§§

(mechanically fastened)3-ply BUR

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 at1-866-583-BLUE (2583) or contact your local building inspector. In an emergency, call 1-989-636-4400.

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 mold formation. No material supplier including Dow can give assurance that mold will not develop in any specificsystem.

Form No. 179-05051X-1209P&MPrinted in U.S.A. ®™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow

For Technical Information: 1-866-583-BLUE (2583) . For Sales Information: 1-800-232-2436THE DOW CHEMICAL COMPANY . Dow Building Solutions . 200 Larkin . Midland, MI 48674

www.dowpmr.com

Documents

United States COMMERCIAL Protected Membrane Roof ...ecatalog.bc.com/.../SiteContent/1/pdfs/Protected_Membrane_Roof_Installation_Guidelines.pdfProtected Membrane Roof Installation Guidelines