CHAPTER 8 CONSTRUCTION DETAILS - Progressive Materials

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CHAPTER 8CONSTRUCTION DETAILSThe NRCA Roofing Manual: Metal Panel and SPF Roof Systems—2012Chapter 8—Construction Details provides technicalinformation concerning the design and installation ofconstruction details for quality SPF roof systems. Thisintroduction is intended to supplement the specialnotes on the individual construction details.Construction details are provided for the following SPFroof system types: SPF roof systems with protective coatings SPF re-cover roof systems with protectivecoatingsConstruction details applicable to SPF roof systems withprotective coatings are denoted as “SPF-” followed by anumber and possibly a letter (e.g., SPF-2, SPF-2A).Construction details applicable to SPF re-cover roof systems with protective coatings are denoted as “SPF(R)-”followed by a number and possibly a letter (e.g., SPF(R)1, SPF(R)-1A).The letter designation after an SPF roof system type designation and number identifies NRCA’s order of preferencefor addressing a specific detail condition. For example,Construction Detail SPF-3—Base Flashing With Counterflashing depicts NRCA’s preferred method of addressing a base flashing with counterflashing detail for SPFroof systems with protective coatings. Construction Detail SPF-3A—Base Flashing depicts an alternative detailNRCA also considers acceptable based on any limitationsdescribed on the alternative construction details.8.1 Information Applicable to AllConstruction DetailsThe construction details in this manual provide a genericconcept for each specific detail type shown. NRCA’sconstruction details likely will require modification tomeet a project’s specific requirements. It is a designer’sresponsibility to adapt the construction details to aproject’s requirements.NRCA makes these construction details available in acomputer-aided design (CAD) format to allow users tocustomize these construction details using their own CADsoftware applications to suit their specific project needs.The information contained in this manual is intendedThe NRCA Roofing Manual: Metal Panel and SPF Roof Systems—2012SPF Roof Systems Chapter 8—Construction Details333

primarily to address construction details applicable tonew construction. When considering reroofing projects,the Reroofing Manual section of The NRCA RoofingManual: Architectural Metal Flashing, CondensationControl and Reroofing should be consulted regarding thedecision to re-cover or remove existing roof systems andfor general information applicable to reroofing low- andsteep-slope roof systems. Once this decision is made,most information contained within this chapter can alsoapply to reroofing.NRCA suggests this chapter be used in the design of roofsystems only after a number of criteria have been carefullyconsidered, including:In addition, NRCA recommends designers consider thefollowing factors for SPF roof systems.Other Components: Components that may be provided or installed by other trades that are integrated intoroof systems can be critical to the weathertight integrity ofcompleted roof systems. These components may include: Metal counterflashings at curbs and otherpenetrations Lead flashings, drains and plumbing vent stacks Climate and geographic location Drain heads, clamps and strainers A building’s intended use and design lifeexpectancy Sheet-metal vents Exterior and interior temperature and humidityconditions Through-wall flashings Sheet-metal pitch pans Code requirements Skylight components and flashings Type of roof deck Smoke hatch components and flashings Slope and drainage Expansion joints and related components A roof ’s configuration Wood blocking and attachment Building movement Pipe or conduit supports Fire, wind and impact resistance Crickets and saddles Type and amount of insulation needed Siding or cladding Need for ventilation Chimney caps Maintenance, repair and reroofing Wall cladding Compatibility with adjacent components, including potential material discharge onto a roof Permanent safety anchors or guardrails Construction sequencing Lightning protection arresters and cables Worker safety Photovoltaic systems Potential building additions Odors, noise and dust generated by certainsystem application methods Rooftop traffic Reflectivity or emissivityThese criteria play important roles in the success or failure of every roof assembly and must be considered by a334designer to determine the appropriate components of aroof assembly, applicable specifications and constructiondetails to be used. Microwave or satellite dish componentsDefinition of responsibility for the above componentsshould be determined prior to job initiation.Roof Assembly Components—Deck,Insulation and SPF: In all the constructiondetails, unless otherwise noted, the primary components of each construction detail are illustrated asgeneric components.The NRCA Roofing Manual: Metal Panel and SPF Roof Systems—2012SPF Roof Systems Chapter 8—Construction Details

Wood Nailers and Blocking: Many of the construction details illustrated in this manual depict woodnailers and blocking at roof edges and other points ofroof termination. Wood nailers must be adequately fastened to the substrate below to resist uplift loads. Thisespecially is true at parapet walls and copings and roofedges where edge-metal shapes are fastened to woodblocking.Among other advantages, the nailers provide protection forthe edges of rigid board insulation and provide a substratefor anchoring flashing materials. Wood nailers should bea minimum of 2 x 6 nominal-dimension lumber.To provide an adequate base, nailers should be securelyattached to a roof deck, wall and/or structural framing.In the design of specific details for a project, a designershould describe and clearly indicate the manner in whichwood nailers and/or blocking should be incorporated intoconstruction details. A designer should specify the meansof attachment, as well as the fastening schedule for allwood nailers and blocking.Preservative-treated Wood: Preservative-treatedwood available for consumer use no longer is treated withchromate copper arsenate (CCA). Some commercial usesof CCA are still available. The new treatment processesuse alkaline copper quat (ACQ), copper azole (CBA),sodium borates (SBX), ammoniocal copper zinc arsenate(ACZA) or variations of these compounds. Most treatments except SBX are more corrosive than CCA and require fasteners, anchors and connectors of specific composition to resist corrosion.NRCA suggests the following guidelines when encountering the current generation of treated wood: Carbon steel, aluminum and electroplated galvanized steel fasteners and connectors shouldnot be used in contact with treated wood. Hotdipped galvanized fasteners complying withASTM A153, “Standard Specification for ZincCoating (Hot-Dip) on Iron and Steel Hardware,” and connectors complying with ASTMA653, “Standard Specification for Steel Sheet,Zinc-coated (Galvanized) or Zinc-Iron AlloyCoated (Galvannealed) by the Hot-Dip Process,”Class G185, generally are acceptable. Type 304 orType 316 stainless-steel fasteners and connectorsare recommended for maximum corrosionresistance. Fasteners with proprietary anti-corrosion coatings may be acceptable for use with treated wood.When the use of such proprietary coated fasteners andconnectors is being considered, fastener manufacturersshould be consulted for specific information regarding the performance of their products in treated woodand any precautions or special instructions that maybe applicable. Aluminum fasteners, flashings and accessoryproducts should not be used in direct contactwith any treated wood. ACQ-treated wood isnot compatible with aluminum. Uncoated metal and painted metal flashings andaccessories except for 300-series stainless steelshould not be used in direct contact with treatedwood. Metal products except stainless steel maybe used if separated from treated wood by aspacer or barrier, such as a single-ply membraneor self-adhering polymer-modified bitumenmembrane. SPF will not bond well to treated wood andmay need primers or mechanical means toensure adhesion.NRCA is of the opinion the corrosion-related concernsregarding the use of the current generation of treatedwood possibly outweigh the benefits that treated woodprovides as a component in roof assemblies. In many instances, the use of nontreated, construction-grade wood issuitable for use in roof assemblies as blocking or nailersprovided reasonable measures are taken to ensure thenontreated wood remains reasonably dry when in service.Where a specific construction detail provides for a secondary means of waterproofing, NRCA now considersthe use of nontreated, construction-grade wood to be anacceptable substitute for treated wood.Job-site-fabricated Components: A majority ofthe construction details illustrated in this manual depictjob-site-fabricated construction. Many roof system manufacturers offer prefabricated flashing components or haveguidelines that permit the use of materials other thanthose indicated in these details. Flashing materials mayThe NRCA Roofing Manual: Metal Panel and SPF Roof Systems—2012SPF Roof Systems Chapter 8—Construction Details335

vary greatly; individual manufacturer’s requirements shouldbe examined and evaluated for construction compatibility.Penetrations and Clearance: Roof drains, penetrationpockets and vertical sides of curbs often have particularinstallation or attachment requirements, which follow: Interior roof drain bowls and under-deck clampstypically are furnished and installed by others.Clamping rings and dome strainers generally arefurnished by others and installed by a roofingcontractor. Prefabricated flashing, metal sleeves and curbswith premolded pipe flashings are preferred forsealing pipes or irregularly shaped support legs.Penetration pockets or pitch pans are acceptableas a last alternative. Pourable sealer is the recommended top fill material for penetration pockets. Vertical wood curb nailers may be secured to astructural member or the roof deck using additional wood blocking, metal angle supports, or acombination of wood and metal. Curbs mayconsist of prefabricated (insulated where appropriate) metal curbs and, when securing flashingis necessary, should have nailers at the top edge.The maximum amount of space should be provided between pipes, walls and curbs to facilitate proper installation of SPF and flashings. NRCA recommends a minimum of 12 inches of clearance between pipes, a minimum of 12 inches of clearance between pipes and curbsor walls, and a minimum of 24 inches of clearance between walls and curbs. SPF roof systems may have different installation methods that may require different spacings, and certain project conditions may not allow theserecommended clearances. However, adequate space (i.e.,clearance) is required for a mechanic to properly installthe required flashings at these locations. Refer to Figure8-1. Structural supports that penetrate vertically throughthe roof membrane preferably should be square or round.H-, L- and T-shaped structural supports are not preferredbecause they are difficult to flash properly and may be aconstant maintenance problem.Figure 8-1: Guide for clearances between pipes, walls and curbs336The NRCA Roofing Manual: Metal Panel and SPF Roof Systems—2012SPF Roof Systems Chapter 8—Construction Details

Fastener Spacing: Fastener spacing for gasketed fasteners depicted in the construction details generally is between 8 inches and 24 inches. Fastener spacings providedin the details are nominal dimensions.Metal Flashing Components: Because metalshave thermal expansion and contraction characteristicsthat differ from most other roof covering materials, it isadvisable to isolate metal flashings from the primary roofcovering and flashing when possible. NRCA suggestsavoiding, where possible, flashing details that requirerigid metal flanges to be embedded or sandwiched intoSPF coatings.Often, SPF roof systems are terminated with perimeteredge-metal flashing that is commonly referred to as afoam stop. If the foam stop has a vertical height less than1 inch, NRCA recommends installing a V-groove filledwith elastomeric sealant. See Figure 8-2.V-GROOVE SPF AT EDGEAND INSTALL ELASTOMERICSEALANThinder the ability of the wall construction to dissipatemoisture. Proper gauge, girth and continuous cleat fastening should minimize wind-uplift damage. The bottom ofthe exterior vertical face of a coping cap or metal edgeflashing should be a minimum of 1 inch below the uppermost edge of the exterior wall material.Parapet Walls and Roof Decks: Parapet wallsand deck-wall intersections often require specific additional components to accommodate vertical flashings orcoping caps. These items can take various forms and bemade of various materials. Tapered, continuous, rigid shims for top of parapet walls provide positive slope for drainage andmay be composed of wood, insulation, metal orother compatible material. Flashing substrate materials on vertical walls andbacksides of parapets may include brick or concrete masonry, precast or poured-in-place concrete, wood and gypsum board. Through-wall flashing materials, weep holesand masonry caulking are typically furnishedand installed by masonry contractors. Sheetmetal receivers may be furnished by a sheetmetal contractor and installed by masonryand wall/cladding contractors. Prior to installing metal caps, parapet walls needto be covered by a sheet membrane liner.PERIMETER EDGE METALFLASHING (FOAM STOP)Figure 8-2: Perimeter edge-metal flashing (foam stop)Illustrations of metal component joinery, such as concealed or cover plates, are located in the ArchitecturalMetal Flashing section (Details SM-) of The NRCARoofing Manual: Architectural Metal Flashing, Condensation Control and Reroofing. NRCA does not recommend caulking the joint between the bottom of the exterior vertical face of a coping cap or metal edge flashingand building exterior because it does not add to the waterproofing integrity of the assembly and may, in fact, Concrete, masonry, metal and gypsum-boardwalls should be primed in preparation for SPFflashings.Rooftop Equipment and AssociatedFlashing: NRCA does not recommend using a roofas a location for HVAC equipment. Weatherproofingrelated problems may be encountered because of thedesign of an HVAC unit. There often is a lack of clearlydefined responsibility for the weatherproofing of HVACunits among the parties involved, such as contractors,material suppliers and manufacturers.Running conduits and pipes within the interior of rooftopcurbs will minimize rooftop penetrations. Many weatherproofing problems related to HVAC equipment may beattributed to one or more of the following:The NRCA Roofing Manual: Metal Panel and SPF Roof Systems—2012SPF Roof Systems Chapter 8—Construction Details337

Improper design of the equipment’s exteriorshell or housing. This may allow water to enterthe building directly through the unit. Improper design or penetration of condensatepans or drainage lines. This may allow water toenter the building below the HVAC equipment. Improper design of pre-manufactured HVACequipment curbs. There are often no means toproperly terminate base flashings. Inadequate design of the structural framing orroof deck intended to support the weight ofHVAC units. This may result in excessive roofdeflection and subsequent ponding water. Improper flashing of the penetration(s), suchas pipes, conduits and drain lines, that extendthrough the roof to service the HVAC equipment. Lack of service walkways to and around mechanical equipment for rooftop traffic.Expansion Joints: The expansion joints depictedgenerally provide movement capability in longitudinaland transverse directions and must be designed to accommodate the amount of expected movement. It is the designer’s responsibility to determine the amount and direction of expected movement at expansion joints. The expansion joints depicted generally will not accommodateseismic movement. Where seismic movement is expected,alternative details likely are needed.Skylights: Skylights incorporated into SPF roof systems and structural metal panel roof assemblies should beinstalled on curbs so they are out of the drainage plane—that is, above the plane of roof panels. Skylight framesshould overlap the curb a minimum of 3 inches to actas counterflashing, or separate counterflashing shouldbe installed.materials. Drain sumps are recommended at all internaldrain locations.Drain sumps reduce the potential for localized ponding atdrain locations because of a buildup of materials and adrain clamping ring. Drain sumps should be round andsized equal to the drain bowl diameter plus 24 inches. Forexample, if a drain bowl’s diameter is 12 inches, the drainsump should be approximately 36 inches in diameter.Slope for drain sumps is recommended to be 11 2:12. SeeFigure 8-3.To accommodate the 11 2-inch-per-foot taper for each sideof the drain sump, the drain bowl flange must be set at alevel that is 11 2 inches below the height of the insulationat the outer edge of the drain sump. The chart providesthe height of the drain bowl above the roof deck based onthe insulation thickness at the outer edge of the drainsump. See Figure 8-4.Crickets and Saddles: The use of tapered insulation or SPF may not necessarily result in complete, immediate drainage of SPF surfaces. Some residual surfacewater may remain on the SPF surfaces at junctures, transitions and immediate drain areas following periods ofrain. To help reduce the amount of residual surface waterbetween drains, behind curbs and along roof edges between scuppers, NRCA recommends installing cricketsand saddles. Figures 8-5 (page 340) and 8-6 (page 341)provide additional information regarding cricket andsaddle slope and length-to-width (L:W) ratios.Surface Protection: Prior to the application of SPF,provide masking protection to prevent the overspray ofmaterials onto surfaces not intended to receive SPF andprotective coating. In addition, mask, seal or cover HVACand ventilation equipment and building air intakes nearthe work area.Skylights require fall protection. NRCA suggests permanent internal or external fall-protection devices be included at all skylights.Drains and Drain Sumps: NRCA recommendsthe use of cast-iron drain bowls, clamping rings and strainers at internal drain locations. Cast iron is the only material that will meet building code requirements for drain338The NRCA Roofing Manual: Metal Panel and SPF Roof Systems—2012SPF Roof Systems Chapter 8—Construction Details

Figure 8-3: Drain sump guidelinesFigure 8-4: Recommended drain bowl heightsThe NRCA Roofing Manual: Metal Panel and SPF Roof Systems—2012SPF Roof Systems Chapter 8—Construction Details339

SUMPEDROOF DRAINCURBEDPENETRATIONSADDLELW24" MIN.CLEARANCESLOPESUMPEDROOF DRAINCANTCRICKETRECOMMENDED MAXIMUM L:W RATIOSFOR SADDLES AND 3:11/41/23:11/21/24:1Figure 8-5: Guide for crickets and saddles340The NRCA Roofing Manual: Metal Panel and SPF Roof Systems—2012SPF Roof Systems Chapter 8—Construction Details

RAISED PERIMETER LOP24" MIN.CLEARANCEECURBED PENETRATIONCRICKETRECOMMENDED MAXIMUM L:W RATIOSFOR 43:11/41/23:11/21/24:1Figure 8-6: Guide for cricketsThe NRCA Roofing Manual: Metal Panel and SPF Roof Systems—2012SPF Roof Systems Chapter 8—Construction Details341

8.2 Index of DrawingsSPF Construction DetailsSPF-1Base Flashing at Parapet Wall with Metal Coping .344SPF-2Perimeter Edge-metal Flashing With Sealant (Foam Stop).345SPF-2APerimeter Edge-metal Flashing (Foam Stop) .346SPF-3Base Flashin

information concerning the design and installation of construction details for quality SPF roof systems. This introduction is intended to supplement the special notes on the individual construction details. Construction details are provided for the following SPF roof system types: SPF roof systems with protective coatings SPF re-cover roof systems with protective coatings Construction .

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