A SPECIALIZED NEEDA roof deck serves as the structural sub-

strate for roofing materials while providingprotection for equipment, products, andpersonnel located below. These basic func-tions require materials that provide long-term, reliable performance.However, many facilities have chemical

exposures or continuous moist conditionsthat can result in a short service life formetal or wood roof decks and produce cost-ly maintenance and premature replacementof the entire system.Corrosive elements can attack uncoated

edges of a steel deck and its fasteningpoints. Moisture will eventually cause woodplanking to rot and deteriorate. Concreteplank decking is sometimes used for harshconditions; however, chemical vapors canpenetrate the porous material, attack itsreinforcing bars, and cause the decking toflake or spall. This can be a concern for per-sonnel safety and can damage equipment orcontaminate finished goods located below.In addition, aged concrete deck planks cansag and, in extreme cases, experience cata-strophic failure and collapse.Facilities that can have these conditions

include natatoriums, food and chemicalprocessors, pulp and paper mills, powerplants, mining and metal treatment facili-ties, and others.

A PROVEN SOLUTIONOffering long and reliable service life, a

properly fiberglass-reinforced plastic (FRP)

roof deck can provide performance exceed-ing that of metal, wood, or concrete deckingfor these types of applications.For corrosive conditions, an FRP roof

deck is a lower-cost alternative than stain-less steel. In addition, when compared toconcrete planks, an FRP roof deck can pro-vide an 11-pound-per-square-foot reduc-tion in dead load on the building structure.As support for either single-ply or built-uproofing, structural FRP decks have deliveredsignificant life cycle cost savings and out-standing performance for many end users.To achieve this levelof performance andacceptance, an FRPdeck must effectivelyaddress all of theseissues:• C h e m i c a land moistureresistance

• L o n g - t e r msupport fordead andwind-upl i f tloads

• Installation• FM and ULrequirements

CHEMICAL ANDMOISTURE RESISTANCETo ensure appro-

priate selection ofmaterials, the poten-

tial effects of chemical or high-moistureexposure should be considered in thedesign and specification stage. Many factorsmust be evaluated, including chemical type,concentration, duration of exposure, andoperating temperature.FRP materials made with an appropriate

polymer resin system can easily resistchemical exposures that are deleterious tometal components. A well-designed FRProof deck does not rust, rot, peel, or flake,thus eliminating the threat of falling parti-cles that can damage equipment or contam-

Chemical Concentration OperatingTemp (˚F)

Chlorine dioxide Fumes 210Chlorine wet gas All 210Copper sulfate All 210Hydrochloric acid 15% 210Hydrogen sulfide All 210Magnesium chloride 100% 210Phosphoric acid 85% 210Sodium chloride All 210Sodium hydroxide Vapor 180Sodium hypochlorite 5% 180Sulfuric acid 50% 210

Table 1

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CHEMICAL RESISTANCE:PREMIUM-GRADE VINYL ESTER

inate product. FRProof decks have anextensive history ofsuccessful use incontinuous wetconditions such asthose found inpapermaking oper-ations.The type of

resin used in theFRP material willaffect its long-termcapability to resistchemical attack.Both vinyl esterand isophthalicpolyester resin sys-tems offer out-standing corrosionresistance. Vinylester materialshave better strengthretention at elevat-ed temperaturesand capacity forsupport of long-term dead loads. Inconsideration of

these factors, premium-grade vinyl esterresin should be the required resin systemfor an FRP roof deck. The chemical resis-tance table (Table 1) provides guidelines forvinyl ester materials in a sampling of chem-ical exposures. See Photo 1.

STRUCTURAL PERFORMANCEIn an FRP material, the primary source

of strength and stiffness is its glass fiberreinforcement. As structural properties arecontrolled by the content and alignment ofthe fibers, glass-reinforcing content mustbe maximized.For a roof deck, it is recommended that

FRP material contain a minimum reinforc-ing content of 50% of its weight, whichshould be a minimum of 1 lb. per sq. ft.(psf). This is virtually twice the amount ofglass-fiber reinforcing that is found in light-duty, chopped strand FRP panels andresults in much higher strength and stiff-ness properties. As translucent roofing andsiding, chopped-strand-reinforced FRP pan-els may be suitable for some applicationswith low structural requirements but not asa structural roof deck.For effective reaction and transfer of

loads within a structural FRP panel, theglass fiber reinforcements should bestraight and continuous and aligned in both

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Photo 1 – A corrosion-resistant FRP roof deck can deliver long, maintenance-free service life in chemicalor high-moisture exposures.

longitudinal and transverse directions. Thereinforcing alignment and glass contentprovide the structural capability necessaryto support the dead load of roofing materi-als and wind uplift loads with minimaldeflection.

The reinforcing content of 50% byweight in straight, continuous, bidirectionalalignment is the basis of design for TuffSpan, the first FRP building panel used as astructural roof deck. This is also a typicalrequirement for other FRP materials used

for demanding structural applications suchas pultruded FRP beams and grating.As a key part in developing the first FRP

material used as a roof deck, engineers con-ducted repetitive, large-scale tests to accu-rately determine material capacity to sup-port long-term, dead, and uplift loads atdeflection levels typical for structural roofdecks. The large-scale tests are the basis forload/span data developed for the FRP decksin Figures 1 and 2 and their accompanyingtables (Tables 2 and 3).For metal deck panels, moment capaci-

ty is typically the limiting factor for deter-mining maximum spans. However, for anFRP profile such as the 6.5 deck, deflectionand stiffness (EI) can be the controllingdesign limits. These can result in longerallowable spans for a two-span conditionwhen compared with a multiple span. Toincrease stiffness and maximum spans,these FRP decks are designed with greaterpanel depth than metal deck units. The 6.5x 2 deck is 2 in. deep versus the 1.5-in.depth of conventional steel B Deck. The 8.0deck is manufactured in 3.5-in. depth ascompared to 3-in.-deep, steel N Deck.

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6.5 X 2 VFR 500

Uniform load, psf 20 30 40 50 60 70 80

Single span 7'0" 6'1" 5'6" 5'1" 4'10" 4'7" 4'4"

Two span 9'4" 8'2" 7'5" 6'11" 6'6" 6'2" 5'10"

Three or more spans 8'7" 7'6" 6'10" 6'4" 6'0" 5'8" 5'5"

Table 2

Figure 1

8.0 X 3.5 VFR 700

Uniform load, psf 20 30 40 50 60 70 80

Single span 9'6" 8'3" 7'6" 7'0" 6'7" 6'3" 6'0"

Two span 12'9" 10'6" 9'1" 8'1" 7'5" 6'10" 6'5"

Three or more spans 11'9" 10'3" 9'4" 8'8" 8'2" 7'8" 7'2"

Table 3

Figure 2

N O V E M B E R 2 0 1 1 I N T E R F A C E • 1 5

DEAD + LIVE / UPLIFT LOADING: L/D=180, FOS=2.5

DEAD + LIVE / UPLIFT LOADING: L/D=180, FOS=2.5

INSTALLATIONOffered in rib profiles similar to conven-

tional steel deck, installation time and pro-cedures for fastening FRP roof deck to sup-ports are similar to those for a metal deck.With lighter weights, the layout of FRP deckpanels is typically quicker and costs lessthan metal units. Compared to concretedecking, installation cost for a much lighterFRP roof deck is significantly lower.Attachment of roofing insulation or

membrane to FRP roof deck can be achievedby the following:• Mechanical (positive lock) fastenerssuch as Enduro NC plastic, SFS-TPR peel rivet, or Rawl speed-locktoggle

• Cold adhesives such as Olybond500, Duro-Grip, or an equal. Upliftdata are available for Olybond 500and Duro-Grip materials used withFRP roof deck.

• Hot bituminous adhesive (if allowed)with temperature not exceedingmaximum value set by the NRCAHandbook of Accepted RoofingKnowledge

See Photos 2 and 3.

FM AND UL LISTINGSFRP roof decks with vinyl ester and a

fire-retardant resin system have a UL Class1 flame spread rating of 25 or less in accor-dance with ASTM E84 testing. FRP roofdeck sections are also UL listed for Class 90uplift, including construction #NM523 for6.5 x 2 VFR 500 and construction #NM524for 8.0 x 3.5 VFR 700.A roofing assembly with FRP 6.5 x 2 roof

deck has FM Global approval for Class 1 fireand Class 1-90 windstorm classification.Other assemblies with FRP roof decks arelisted as Class 2 per FM Report J.I. OTOA9(Table 4).

SUMMARYConventional metal, wood, or concrete

roof decks may not be the best materials forchemical or continuous wet conditions.Structural FRP roof decks constructed with50% reinforcing content, premium-gradevinyl ester, and fire-retardant resin haveproven that they can provide longer servicelife and significant life cycle cost savings forthese challenging structural and environ-mental conditions. The following two casehistories are provided as examples.

Photo 2 – Fastening of FRP roofdeck to supports is similar to ametal deck. Layout of thelighter FRP sheets is faster.

Photo 3 – Mechanical fasteners orcold adhesives are commonly

used to attach roofing membraneand insulation to FRP deck.

Photo 4 – A corrosion-resistant, FRP roof deck can deliver long, maintenance-freeservice life in chemical or high-moisture exposures.

1 6 • I N T E R F A C E N O V E M B E R 2 0 1 1

FM GLOBAL LISTINGS

Table 4

Roof Deck Section 6.5 x 2 VFR 500 8.0 x 3.5 VFR 700Maximum span 6 ft. 3 in. 8 ft.Fastener - washer diameter 1-60 = .729 in.

1-90 = 1.125 in. 1.125 in.Side-lap fastener spacing 18" o.c. 24" o.c.NC insulation fasteners 16 / 4 x 8 board 16 / 4 x 8 boardPolyiso insulation board 1.3 in.-thick minimum 1.3 in.-thick minimumBUR glass felt 3 ply minimum 3 ply minimumWind uplift rating 1-90 1-90Deflection limit L/240 L/240

CASE HISTORY: WEYERHAEUSER PAPERPrior to June 1987, Weyerhaeuser Paper

had tongue-and-groove wood roof deckinstalled on its Longview, Washington,paper mill. According to roof consultantGus Siegrist of A.N.G. Consulting Services,Inc., the roof was leaking, and the deck wasrotting and deteriorating.Expecting that an FRP roof deck would

stand up to the demanding conditions,Siegrist and Weyerhaeuser selected TuffSpan 6.5 VFR 500 roof deck to replace the44,000-sq.-ft. wood roof deck. The FRP roofdeck is still in service after 24 years andhas delivered huge life cycle cost savings forWeyerhaeuser. See Photo 4.

CASE HISTORY: UNIVERSITY OF WEST FLORIDANATATORIUMAs the result of exposure to moist, chlo-

rinated conditions, the coated steel roofdeck at the University of West Florida nata-torium had been weakened by corrosionand seriously damaged during HurricaneIvan. In its search for a replacement mater-ial, STOA Architects included the followingrequirements for the new roof:• Resistance to chlorine vapors• Resistance to hurricane-force, winduplift loading due to its coastal loca-tion

• Compatibility with cold adhesivesfor attachment of roofing materials

STOA identified an FRP roof deck as thematerial that would provide performancesuperior to metal for the environmentalconditions in the natatorium. Installed in2005, the FRP roof deck has met expecta-tions and provided outstanding service. SeePhoto 5.

Roxul® is committed to providing the most

America. As part of that commitment, our stone wool insulation is made from a high percentage of recycled materials which helps contribute to LEED® points.

We have also gone one step further. Our commercial roof insulation can now be fully recycled! This commitment means that architects, consultants or other design professionals can specify ‘Roxul on the Roof’ knowing that should the time come

Subject to terms and conditions set out by Roxul, our stone wool insulation can be removed from a project site, sent to Roxul and be fully recycled into new material.

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e have also gone one step furtherWcommitment This recycled! fully

professionals can specify ‘Roxul on the Roof

Subject to terms and conditions set out by Roxul, our stone wool insulation can be removed from a project site, sent to Roxul and be fully recycled into new material.

pcontribute to LEEDis made from a high percentage of recycled materials which

. Our commercial roof insulation can now be ne step furtherarchitects, that means mmitment

knowing that should the time come ’ecify ‘Roxul on the Roof

conditions set out by Roxul, our stone wool insulation can be ct site, sent to Roxul and be fully recycled into new material.

points.

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Photo 5 – FRP roof decks are a suitablesubstrate for either single-ply or built-up roofing.

Tom Toler has held senior management positions for bothsteel and FRP building panel manufacturers. During hiscareer, Toler has contributed to the development of severalFRP products, including FRP roof and form deck, FRP roofingpanels supporting foot traffic, the first FRP exterior claddingto achieve FM approval, long-span FRP structural shapes,and FRP louvers and ridge vents. He served on the committeefor the Society of Plastics Institute that developed ASTM3841, the standard for fiberglass-reinforced plastic buildingpanels. Tom is currently product manager for building andenvironmental products for Enduro Composites, Inc., located in Houston, Texas.

Tom Toler

N O V E M B E R 2 0 1 1 I N T E R F A C E • 1 7