ROOF DECK SECUREMENT AND ABOVE-DECK ROOF COMPONENTS

Transcription

1 FM Global Property Loss Prevention Data Sheets 1-29 September 2010 Page1of40 ROOF DECK SECUREMENT AND ABOVE-DECK ROOF COMPONENTS Note to Insureds of Factory Mutual Insurance Company: Contact the local FM Global office before beginning any roofing work. Table of Contents Page 1.0 SCOPE Changes LOSS PREVENTION RECOMMENDATIONS Introduction Construction and Location General Vapor Retarders (Barriers)Design and Installation Recommendations Roof Insulation Insulation and Roof Cover Fasteners Recover and Reroof ConstructionDesign and Installation Recommendations Structural Concrete, FM Approved Fiber Reinforced Cement and Lightweight Insulating Concrete (LWIC) Decks: Design and Installation Recommendations Single-Ply Membrane Covers and Multi-Ply covers with Mechanically Attached Base Sheets Asphalt and BUR Installation Recommendations Roof Covers Adhered to Mechanically Attached Base SheetsFastener Installation Recommendations Liquid Applied Roof CoversInstallation Recommendations Mechanically Fastened Base Sheet Assemblies Over Wood DecksDesign and Installation Recommendations Roof Deck Span and Securement for Wind Loads Lightweight Insulating Concrete Roof Decks Cementitious Wood Fiber Roof Deck Recommendations Lumber and Plywood Deck Structural Concrete Roof Deck Recommendations Torch Application of Modified Bitumen Roof Covers Field Wind Uplift Tests Cold-Process Adhesives Fiberglass Reinforced Plastic (FRP) Roof Deck SUPPORT FOR RECOMMENDATIONS Supplemental Information Class 1 and 2 Roof Decks Wind Uplift Resistance, Non-Ballasted Roof Covers Wind Uplift Resistance, Ballasted Systems Compatibility With Substrate External Combustibility Recover Construction Wind Uplift Wind Damage Inferior Construction Steel Deck No part of this document may be reproduced, stored in a retrieval system, or transmitted, in whole or in part, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without written permission of Factory Mutual Insurance Company.

2 Page 2 FM Global Property Loss Prevention Data Sheets 4.0 REFERENCES FM Global Others APPENDIX A GLOSSARY OF TERMS APPENDIX B DOCUMENT REVISION HISTORY List of Figures Fig. 1. Hailstorm hazard map for United States (areas between dashed lines subject to severe hailstorms and need an SH hail rated roof) Fig. 2. Insulation and vapor barrier mechanically fastened to steel deck Fig. 3. Fastener placement 2 4 ft ( m) boards Fig. 4. Fastener placement 3 4 ft ( m) boards Fig. 5. Fastener placement 4 4 ft ( m) boards Fig. 6. Fastener placement 4 8 ft ( m) boards Fig. 7. Alternate corner increase for mechanically attached single-ply membranes Fig. 8. Fastener layout for 36 in. (914 mm) wide base sheet Fig. 9a. Side lap fastening: interlocking seam Fig. 9b. Side lap fastening: overlap seam Fig. 10. Two deck fasteners per support, one into each bar joist top flange Fig. 11. Torch application of upper ply to a mechanically fastened base sheet Note adhesive pooling at the leading edge of the roll Fig. 12a/12b. 4 4 ft ( m) insulation boards secured with nine fasteners per board List of Tables Table 1. Recommended Rating of Field, Perimeter, and Corner Areas (Zones 1, 2, and 3) for Enclosed Buildings... 5 Table 2. Weight Needed of No. 3 Round Stone Ballast, Parapet 36 in. (914 mm) Table 3. Weight Needed of No. 3 Round Stone Ballast, Parapet > 36 in. (914 mm) Table 4. Weight Needed of Paver Blocksnot T&G, Beveled or Strapped to Each Other, Parapet 36 in. (914 mm) Table 5. Weight Needed of Paver Blocksnot T&G, Beveled or Strapped to Each Other, Parapet > 36 in. (914 mm) Table 6. Weight Needed of Paver BlocksT&G, Beveled or Strapped to Each Other, Parapet 36 in. (914 mm) Table 7. Weight Needed of Paver BlocksT&G Beveled or Strapped to Each Other, Parapet > 36 in. (914 mm) Table 8. Base Sheet Fastener Coverage for Non-FM Approved Combinations, ft 2 per Fastener Table 9. Standard 36 in. (0.9 m) Base Sheet Fastening (Non-FM Approved Components). (See Fig. 8.). 24 Table 10. Minimum Metal Disk or Fastener Head Size (Base Sheet Fasteners) Table 11. Allowable 2 Uniform Uplift Pressure Table 12. Nail pullout strength per in. (25 mm) of penetration... 31

3 Roof Deck Securement and Above-Deck Roof Components 1-29 FM Global Property Loss Prevention Data Sheets Page SCOPE This data sheet provides recommendations for the proper securement of various roof decks to supporting members, and for the proper design and installation of above-deck roof components. Items covered include roof covers, insulation, vapor retarders, fasteners, and recover assemblies. This data sheet is intended to be used in conjunction with Data Sheet 1-28, Wind Design. Prefabricated panel roofs, lap seam, and standing seam roofs are covered in Data Sheet 1-31, Metal Roof Systems. Other data sheets with information on roofing include: Data Sheet 1-28, Wind Design Data Sheet 1-30, Repair of Wind Damaged Roof Systems Data Sheet 1-32, Existing PVC Roof Covers Data Sheet 1-33, Safeguarding Torch-Applied Roof Installations Data Sheet 1-49, Perimeter Flashing Data Sheet 1-52, Field Uplift Tests Data Sheet 1-54, Roof Loads For New Construction (which covers positive [snow, ponding] loads) For roofs of buildings divided by maximum foreseeable loss (MFL) fire walls, refer to Data Sheet 1-22, Criteria for Maximum Foreseeable Loss Fire Walls and Space Separation. 1.1 Changes September Minor editorial changes were made for this revision. 2.0 LOSS PREVENTION RECOMMENDATIONS 2.1 Introduction The recommendations provided in this document are not intended to supersede the requirements of any FM Approval (see Appendix A for definition). FM Approval listings outline the field-of-roof securement requirements. Some listings also may contain specific roof corner/perimeter fastening methods. This data sheet outlines other roof perimeter/corner fastening methods. Use the recommendations to supplement the listings in the Approval Guide, a publication of FM Approvals. Where appropriate, recommendations are grouped in each section as Design, Installation, and Maintenance. Roof systems are FM Approved only for certain wind uplift ratings. All recommendations are for systems used within their FM Approval limits. Generally, recommendations regarding internal fire ratings (Class 1 or 2) are not applicable to structural concrete and gypsum roof decks, as these decks are rated noncombustible (internally) regardless of the above-deck components due to the substantial thermal barrier offered by the deck itself. Form boards used with gypsum decks may themselves be combustible. 2.2 Construction and Location General These recommendations are applicable to all systems except as noted Design Recommendations Except for ballasted systems that are not FM Approved, ensure all installations use components and systems (roof deck, insulation, fasteners, roof cover, etc.) that are FM Approved for use together on the particular deck. Use of individually FM Approved components, not FM Approved for use together, does not

4 Page 4 FM Global Property Loss Prevention Data Sheets constitute an FM Approved or recommended assembly. Use of FM Approved systems is universally recommended and is implied for all applicable assemblies whether or not specifically stated in the recommendation All FM Approved materials are required to have the FM Approval mark on the packaging or the material itself. Materials without proper labeling are not FM Approved and cannot be accepted Ensure the roof deck design and installation are in accordance with the Approval Guide, RoofNav and Data Sheets 1-28, Wind Design, 1-49, Perimeter Flashing (and 1-31, Metal Roof Systems, where applicable) Use FM Approved perimeter flashing systems, where available. Secure wood nailers in accordance with Data Sheet 1-49, Perimeter Flashing, and follow other guidelines in that document where FM Approved flashings are not available Ensure roof slope is a minimum of 1 ( 1 4 in./ft, 21 mm/m). This can be accomplished by varying the column heights or using an FM Approved tapered insulation system. Refer to Data Sheet 1-54, Roof Loads for New Construction Installation Recommendations It is essential that thorough supervision by the building owner s qualified representative is provided during all roof construction to ensure quality of workmanship and adherence to FM Approval standards and project specifications When installing torch-applied roof covers, follow the recommendations in Data Sheet 1-33, Safeguarding Torch-Applied Roof Installation, and recommendation Do not store combustible roofing materials in buildings under construction unless an adequate sprinkler system is in service. Use combustible adhesives and solvents with caution. Use FM Approved safety cans where appropriate. Do not allow smoking on roofs at any time. Do not allow flammable liquids or solvents to enter confined spaces. Ensure the facility s emergency response team oversees all roofing work Make a minimum of two 10 lb (4.5 kg) ABC fire extinguishers available on the roof during roof construction and repairs Due to possible high concentrated loads from the rolls of membrane and gravel carts, caution is needed when moving these materials across the roof. To prevent over-stressing the deck when the weight of individual rolls of single-ply membrane exceeds 1100 lb (500 kg), use precautions such as shorter deck spans or plywood sheets over steel deck to reduce point loads Fill the space between nailers in roof expansion joints with noncombustible, compressible insulation such as glass, mineral, or ceramic fiber type Provide adequate separation and/or noncombustible insulation between hot exhaust stacks and combustible roof deck and above deck roof components. See DS 1-13, Chimneys, for details Ensure roof insulation or cover boards are dry and surfaces are free of debris or dirt prior to adhering roof covers to them. This will help ensure complete adhesion of the cover to its substrate Maintenance Recommendation Inspect roof systems and flashing semi-annually and after storms. During inspection, note and repair any holes or deterioration of the covering, opened seams, backed-out fasteners, loose anchorages, loose flashing, membrane shrinkage, etc. Replace any wet insulation when making roof repairs. Inspect and clean drains as needed. Maintain written records Wind Uplift Resistance: Design Recommendations Determine the roof wind uplift design pressure and recommended FM Approvals wind uplift ratings for roof assemblies (decks and above-deck components) per Data Sheet 1-28, Wind Design or RoofNav Ratings Calculator. Do not use any system beyond its FM Approval rating, except where enhancements are allowed by this document.

5 Roof Deck Securement and Above-Deck Roof Components 1-29 FM Global Property Loss Prevention Data Sheets Page Ensure all new, re-roof, and recover construction uses an appropriate wind-uplift-rated FM Approved roof system where available. Ensure the roof field fastening is per FM Approvals RoofNav listing. Note: For ballasted systems, see sections to Because there are higher uplift forces on the roof corners and perimeter, these areas need additional securement over that, which is FM Approved for the field of the roof. Refer to Data Sheet 1-28 for corner/perimeter definitions and dimensions. Ensure any whole or partial insulation board or roof cover/base sheet width (when the roll is parallel to the building edge) that falls within the calculated perimeter or corner has the increased securement applied over the entire board or roof cover/base sheet width. There are several acceptable methods for increasing the uplift resistance of the roof in the corners and perimeters. Do one of the following: Where the FM Approvals RoofNav listing includes a roof perimeter and/or corner fastening method, it can be used. Use a roof system with the appropriate FM Approval wind uplift rating in each area per Table 1. Use the appropriate prescriptive recommendation noted in section , within the limits of acceptability. An alternative is to use an adhered roof cover (adhered across the entire roof) that is adequately wind rated for the field of the roof and, in the perimeter and corner areas, use a mechanically attached roof cover (see Table 1 and ) that is either: a) FM Approved for wind pressures in the perimeter and corner areas, or b) FM Approved for the field of roof pressure per Table 1 and enhanced in the perimeter and corner areas per recommendation by reducing the distance between rows of fasteners. In either case a) or b) above, fasten a termination bar over the cover or base sheet (with suitable weatherproofing provided) and into the deck every 6 in. (150 mm) on center. Use minimum no. 15 screws at the junction of the fully adhered areas with the adhered and mechanically fastened areas. Table 1. Recommended Rating of Field, Perimeter, and Corner Areas (Zones 1, 2, and 3) for Enclosed Buildings Minimum Wind Rating for FM Approved Deck/Above-Deck/Entire 1 Assembly Roof Field Area Design Pressure, p, (psf) 2 Roof Field Area Enclosed Bldg. Roof Perimeter Area Enclosed Bldg. Roof Corner Area Enclosed Bldg. p <p < p <p < p <p < p <p < p <p < p <p < p <p < p Base the minimum wind rating on the roof field area rating when perimeter/corner areas are enhanced per this data sheet and other pertinent FM Global Data Sheets (1-29, 1-31, etc.). Base the minimum wind rating on the respective area rating when perimeter/corner area enhancements are not done, or are not acceptable. 2 For roofs with higher field area design pressures, or to interpolate needed perimeter and corner ratings when the field requirements are between levels, multiply the needed field area design pressure from Table 3, 4 or 5 (of D.S. 1-28) by a safety factor of 2.0 and the respective pressure coefficient per Table 6 of D.S. 1-28, and round up to the next highest 15 psf rating interval. 3 Ratings above apply to enclosed buildings, with roof slopes 7 and roof heights 60 ft (18 m).

6 Page 6 FM Global Property Loss Prevention Data Sheets Prescriptive Enhancement Options: Perimeter and Corner a) For all deck types, where roof covers are adhered to some combination of mechanically fastened insulation, cover board, or thermal barriers, prescriptive enhancements may be used for securement of the perimeter and corner areas, as long as one of the conditions below applies: 1. The building is in a non-hurricane prone region where the design wind speed does not exceed 90 mph and the roof height does not exceed 75 ft (23 m). Note the roof height is limited to 30 ft (9.1 m) if the building is located in surface roughness exposure D (see DS 1-28) and the building is partially enclosed. Or, 2. The recommended field of roof rating needed per DS 1-28 does not exceed Class 1-75 (3.6 kpa). Or, 3. The building is in a non-hurricane-prone region (see Appendix A) and the recommended field of roof rating per DS 1-28 does not exceed Class 1-90 (4.3 kpa). For any of the three conditions above, increase the number of fasteners per board over the FM Approved field-of-roof spacing by the following: 50% minimum in the roof perimeter, but at least one fastener per 2 ft 2 (1 per 0.19 m 2 ). It is not necessary to install fasteners closer than one per 1 ft 2 (1 per 0.09 m 2 ). One fastener per 1 ft 2 (1 per 0.09 m 2 ) in corner areas. Round up to the next whole number of fasteners, if necessary b) For all locations (including hurricane-prone regions), where a Class 1-90 wind rated system is needed for the field-of-roof, use the following generic assemblies in the perimeter and corner areas to provide acceptable wind resistance in those areas: Option 1 Minimum in. (38 mm) thick, FM Approved, Class 1 insulation laid loose directly on the deck. Minimum 1 2 in. (12. 7 mm) thick, FM Approved, water resistant, primed (factory or field primed) gypsum cover board over the insulation. Primer can be omitted if roof cover / coverboard combination meets a Class or greater without a primer. Through-fasten both layers to the steel deck with FM Approved minimum No. 14 ( 1 4 in., 6.4 mm) screws and flat-bottom metal stress plates. Use 24 fasteners per 4 by 8 ft (1.2 by 2.4 m) board in the perimeter, and 32 fasteners per 4 by 8 ft (1.2 by 2.4 m) board in the corners. Roof cover a fully mopped, minimum 3-ply BUR; or a minimum 2-ply mod bit system with all plies fully mopped and/or torch applied per FM Approval requirements. Option 2 Minimum 2 in. (50 mm) thick, FM Approved, Class 1 insulation laid loose directly on the deck. Note: a lesser insulation thickness may be used if included in any Class 1 fire-rated assembly with the other components above it, but not less than in. (38 mm) thick. Minimum 7 16 in. (11.1 mm) thick, oriented strand board (OSB) cover board over the insulation. Ensure the OSB is APA (American Plywood Association) rated for Exposure 1, with exterior type adhesive. Through-fasten both layers to the steel deck with FM Approved minimum No. 14 ( 1 4 in., 6.4 mm) screws and flat-bottom metal stress plates. Note: if screws have oversized heads and are specifically approved for OSB or OSB composite boards, stress plates are not required. Use 24 fasteners per 4 by 8 ft (1.2 by 2.4 m) board in the perimeter, and 32 fasteners per 4 by 8 ft (1.2 by 2.4 m) board in the corners. Roof cover a minimum 3-ply BUR or minimum 2-ply mod bit system with all plies fully mopped, per FM Approval requirements.

7 Roof Deck Securement and Above-Deck Roof Components 1-29 FM Global Property Loss Prevention Data Sheets Page 7 c) For areas where the criteria in the recommendations above are exceeded, ensure the roof system used in the perimeter and corner areas is FM Approved for the specific wind rating recommended in the perimeter and corner areas (see Table 1). Alternatively, install either a mechanically attached single-ply membrane, or a multi-ply roof cover with a mechanically attached base sheet in accordance with Note: Insulation and thermal barriers under mechanically fastened roof covers in assemblies that DO NOT incorporate air or vapor retarders do not have to increase the insulation fastening over the field of roof spacing For components adhered with urethane-based adhesives, asphalt, or other adhesives in ribbons, spots, etc., reduce the spacing between ribbons or spots over the FM Approved field-of-roof spacing as noted below (round down to a dimension that is practical with respect to board sizes, etc.): In the roof perimeter, not more than 60% of the field-of-roof spacing between rows or area In the roof corners, not more than 40% of the field-of-roof spacing between rows or area Note: If the FM Approval rating for wind meets the criteria in Table 1 for the perimeter or corner area, no further reduction is needed in those areas. Example: A particular roof cover as FM Approved is adhered with a urethane-based adhesive in ribbons at 1 ft (0.3 m) on center in the field of the roof. The perimeter would need a ribbon spacing of 6 in. (150 mm) and the corners would need a ribbon spacing equal to 4 in. (100 mm) on-center. Note: these spacings were rounded down slightly for practicality For mechanically attached single-ply membranes, and multi-ply covers with a mechanically attached base sheet, refer to section For mechanically attached base sheets, refer to section or if the base sheet is fastened directly to a wood deck For ballasted systems, refer to section For steel decks, increase the number of deck fasteners at each joist or purlin support over the field-of-roof FM Approvals RoofNav listing in accordance with Shorter spans that yield an equivalent increase in deck securement strength are acceptable, but may not always be practical External Fire ResistanceDesign Recommendations Assemblies having an American Society for Testing and Materials (ASTM) E108 Class A rating are preferred in all cases, and are specifically recommended as follows: a) Where the exterior fire exposure to the roof is severe. b) On the entire roof of buildings subdivided by MFL fire walls. Refer to Data Sheet 1-22, Criteria for Maximum Foreseeable Loss Fire Walls and Space Separation, for details on additional surface protection needed adjacent to the wall and roof protection for buildings where MFL space separation is a factor. c) For occupancies particularly susceptible to smoke or water damage ASTM E108 Class C rated assemblies are not recommended on any roofs >10,000 ft 2 (930 m 2 ) The use of pea gravel surfacing installed in accordance with is considered to provide a Class A exterior fire exposure rating. While not normally recommended in hurricane-prone regions due to its potential to become windborne debris, it may be accepted in hurricane-prone regions (such as where required adjacent to fire subdivisions), provided that all gravel remaining at the end of the installation is fully embedded into the bitumen and there is no loose gravel nested on top. The following method will provide such compliance: a) Aggregate is applied into a flood coat of hot bitumen, and allowed to cool and harden. b) Loose aggregate is pushed away, a second flood coat is applied, and the loose gravel is applied back into the second flood coat and allowed to cool and harden. c) Any remaining loose gravel is removed from the site.

8 Page 8 FM Global Property Loss Prevention Data Sheets Hail Resistance: Design Recommendations Use only FM Approved roof cover systems meeting the severe hail (SH) criteria in the hail storm hazard area shown in Figure 1. Unless specifically FM Approved with other surface treatments, built-up roofs (BUR) may be used in SH and MH areas, provided: they are covered with gravel at a minimum of 400 lb per square (19.5 kg/m 2 ) or slag at a minimum of 300 lb per square (14.6 kg/m 2 ). (See Appendix A, Glossary, for definition of square.) aggregate is in accordance with ASTM D1863. aggregate is applied into a minimum 60 lb per square (2.9 kg/m 2 ) bitumen flood coat. Note: Do not use pea gravel in regions prone to hurricanes, typhoons ancd tropical cyclones except where installed in accordance with section Otherwise, use FM Approved coatings in lieu of pea gravel For U.S. locations outside the hail area, MH or SH rated systems can be used At locations outside the U.S., MH rated systems can be used unless local weather records indicate the need for greater hail resistance. Generally, consider SH rated systems for locations with an average of three or more hail storms per year Internal Fire ResistanceNoncombustible, Class 1, and Class 2 AssembliesDesign and Installation Recommendations As all FM Approved roof systems are Class 1 or noncombustible, Class 1 or noncombustible assemblies are recommended in all cases. When there is an existing Class 2 deck and an unsprinklered concealed space below the deck, refer to Data Sheet 1-12, Ceilings and Concealed Spaces, for fire protection guidance Class 2 steel roof decks can be converted to Class 1 by applying an FM Approved undercoating. If this is done, adhere to the following recommendations: Ensure the underside of the deck is clean before coatings are applied. Ensure FM Approved coatings are applied by applicators licensed by the coating manufacturer. Do not use cellulose-based undercoatings in high humidity occupancies as the fire retardant chemicals are water soluble and can leach out of the coating. Do not use steel deck undercoatings where combustible residue can accumulate on the surface Vapor Retarders (Barriers)Design and Installation Recommendations These recommendations outline vapor retarder applications that maintain Class 1 and appropriate wind uplift ratings If a vapor retarder is used, ensure it is FM Approved and applied in a single layer placed directly on the deck. Side and end laps are sealed using FM Approved adhesive. The remaining roof components are then installed with fasteners driven through the retarder into the deck (Fig. 2). The components above the FM Approved vapor retarder can be any combination of materials FM Approved for use together on the particular deck. Some systems are FM Approved with the retarder installed above a base layer of insulation; see section below On panel-type decks (decks with seams such as steel, wood, pre-cast planks, etc.), if a vapor retarder is installed below the insulation or coverboard of a mechanically secured single-ply membrane (per recommendation above), secure the insulation or coverboard with FM Approved insulation fasteners and plates using one of the following options: 1. A rate of 1 per 2 ft 2 (1 per 0.19 m 2 ) throughout the entire roof area, OR 2. A rate throughout the entire roof area that will obtain a minimum 1-90 uplift FM Approval with an adhered single-ply roofing membrane as specified in a RoofNav listing. The insulation/coverboard type used below the mechanically secured membrane must match that specified by the RoofNav listing for the adhered membrane, and the thickness of the insulation/coverboard must be equal to or greater than that specified by the RoofNav listing. A vapor retarder is located on the warm side of the roof or sandwiched between insulation layers. The vapor retarder is sealed to the exterior walls of the building, but not necessarily to the underside of the roof cover.

9 Roof Deck Securement and Above-Deck Roof Components 1-29 FM Global Property Loss Prevention Data Sheets Page 9 Gander Churchill St. Johns Hudson Bay Buchans Gulf of St. Lawrence Ja mes Bay Sidney Charlottetown Chatham Halifax Quebec Sioux Lookout Bangor Montreal Winnipeg Seattle Port Arthur Spokane Montpelier Ottawa Portland In ternational Falls Concord Saranac Lake Boston Duluth Toronto Helena Fargo Bismarck Albany Baker City Providence Hartford Aberdeen Buffalo Boise Philadelphia Ludington Sheridan Pierre Minneapolis Pittsburgh Detroit Trenton Milwaukee Pocatello Harrisburg Sioux Falls Eureka Baltimore Cleveland Red Bluff Lander Chicago Washington DC Fort Wayne Moline Reno Columbus Cincinnati North Platte Sacramento Salt Lake City Indian apolis Kahoka San Francisco Norfolk Charleston Springfield Kansas City Topeka Saint Louis Louisville Wytheville Fresno Knoxville Wichita Ashville Springfield Las Vegas Nashville Joplin Memphis Santa Fe Chattanooga Charleston Amarillo Atlanta Phoenix Birmingham San Diego Savannah Montgomery Tucson Dallas Mobile El Paso Jacksonville New Orleans Tampa San Antonio Houston Gulf of Mexico Miami NEWFOUNDLAND Prince Rupert CANADA Prince George Edmonton The Pas Prince Albert Amherst Saskatoon Kamloops C algary Vancouver Penticton Kapuskasing Regina Nelson Cranbrook Medicine Hat Gulf of Maine Havre Sault St Marie Huntsville Lake Superior Marquette London Green Bay Souix City Des Moines Cheyenne Richmond Denver Williston Lake Huron Billings Lake Michigan Atlantic Ocean Raleigh Pueblo Fort Smith Little Rock Shreveport Jackson Columbia Los Angeles Oklahoma City Gulf of California MEXICO Fig. 1. Hailstorm hazard map for United States (areas subject to severe hailstorms and need an SH hail rated roof) H ecate Strait Clayoquot Victoria Pacific Ocean Exposure to Damaging Hailstorms Moderate Severe No Data Kilometers Miles 2009 Factory Mutual Insurance Company. All rights reserved

10 Page 10 FM Global Property Loss Prevention Data Sheets Fig. 2. Insulation and vapor barrier mechanically fastened to steel deck. An air barrier is used with a mechanically fastened roof cover and is located directly above the roof deck. The air barrier is sealed to the underside of the roof cover, but not necessarily to the exterior walls of the building. In theory, an air barrier improves wind uplift resistance of the roof assembly by preventing air flow into the space below the roof cover and transferring a portion of the uplift load to the insulation. It should be noted that even for properly installed air barrier systems, roof penetrations made after the installation of an air barrier system can hamper the wind performance of an air barrier system if the air barrier is not sealed to the underside of the roof cover after the penetration cut is made. Consequently, there are special FM Approval restrictions on air barrier systems Fastener penetration of the vapor retarder can be avoided by using an FM Approved fastened/adhered assembly. Ensure all materials are FM Approved for use in combination. Ensure substitution of materials is not made Do not mop asphalt/felt vapor retarders directly on to any deck (this would result in a Class 2 roof) except structural concrete Roof Insulation Design Recommendations Ensure insulation boards are FM Approved for the specific application, including specific roof cover, fasten/mop construction, multiple layers, etc. Using assemblies that are not FM Approved can result in a Class 2 and/or inferior roof construction. However, combinations that may not be FM Approved but can be accepted are noted in sections , , and It is acceptable to use multiple layers of FM Approved insulation, mechanically secured through all layers, provided all of the following are true: All layers are the same insulation. The total insulation thickness is not greater than the maximum FM Approved thickness of the insulation. The mechanical fastening and wind uplift rating are per the FM Approval of the top layer. The roof cover/insulation/fastener combination is FM Approved Insulation board sizes listed in the Approval Guide are the minimum FM Approved sizes. Boards up to 4 8 ft ( m) can be used except as noted in section (with a proportional increase in fasteners, adhesive ribbons, etc. rounding up to the next whole number). Do not use boards smaller than FM Approved except per section

11 Roof Deck Securement and Above-Deck Roof Components 1-29 FM Global Property Loss Prevention Data Sheets Page The maximum recommended insulation board size, if the board is adhered with asphalt or adhesive, is 4 4 ft ( m). Exception: Flexible boards such as maximum 1 2 in. (13 mm) thick wood fiber or 5 8 in. (16 mm) gypsum board may be adhered at board sizes up to 4 8 ft ( m) Installation Recommendations Stagger insulation board joints in one direction (the shorter sides staggered if boards are not square). Support the two opposite sides of each board on steel deck flanges, as close as practical to the center of the flange with a minimum bearing width of 1 in. (25 mm). Trim board edges if they veer off the flange center When insulation boards are cut, as is common at the roof edge to produce staggered joints, secure each piece with the appropriate number of fasteners, adhesive ribbons, etc. for the full board times the percentage area of the piece, rounding up to the next whole number Install only as much insulation or gypsum-based board as can be covered each working day. Seal loose roof cover edges at the end of each day to minimize moisture damage. Do not allow water to run in steel deck ribs under completed roof sections Ensure insulation is set on pallets or dunnage and protected from the weather and sunlight prior to installation. Do not allow plastic to cover the insulation as it can allow condensation. A breathable material, such as canvas, is recommended Ensure FM Approved job-mixed material (like LWIC) is installed by applicators licensed by the manufacturer. Steel deck that meets the insulation manufacturer s span and gauge requirements is necessary to support the application equipment. Such systems are a possible option when penetration of the deck with mechanical fasteners is not desired Provide preliminary securement of insulation boards when mechanically fastened roof covers are used (single-plies or multi-plies with fastened base sheets). Install a minimum of two fasteners per4x4ft(1.2 x 1.2 m) board or four fasteners per 4x8ft(1.2 x 2.4 m) board, unless the manufacturer requires a greater number. Additional insulation fastening is not required in the perimeter and corner areas. Where a vapor retarder is used below a mechanically fastened roof cover, see section Insulation and Roof Cover Fasteners Design Recommendations FM Approved insulation fasteners are the only FM Approved and recommended method of securing insulation boards or other boardstock materials to steel deck. Some fasteners are FM Approved for other deck materials When fastener pull-out tests are performed on new construction to evaluate the deck integrity or evaluate decks that are not FM Approved, run a minimum of five tests and use the average value. See section for the number of tests for recover/reroof construction When pull-out tests are done, base the fastener density on the more conservative of either the FM Approved spacing for the fastener plate/insulation/roof cover combination, or the spacing needed based on the average pull-out performance. Example: An existing deck is oriented strand board (OSB). The fastener/insulation/roof cover combination is FM Approved for 4 fasteners per 4 4 ft ( m) board for Class 1-90 on steel deck. The calculated load per fastener would be 360 lb (1600 N) ([4 ft 2 /fastener][90 psf] = 360 lb/fastener). If the proposed fastener achieved a pull-out resistance of 360 lb (1600 N) or more in the deck, the FM Approved spacing would be used. If the fastener achieved a resistance of less than 360 lb (1600 N), for example 300 lb (1335 N), calculate the spacing as follows: (16 ft 2 )(90 psf)/(300 lb) = 4.8 fasteners per board; use five fasteners per board in the roof field. Additional fasteners would be needed in the corners and perimeter per section The percentage increase would be applied to five fasteners per board, not four Installation Recommendations Install fasteners only through dry substrates. Wet constructions can cause deterioration of fasteners, including FM Approved corrosion-resistant fasteners. Exception: Fasteners FM Approved for use in new lightweight insulating concrete decks are designed to be tolerant of the moisture present at the time of installation.

12 Page 12 FM Global Property Loss Prevention Data Sheets Use only FM Approved fastener/plate combinations. Do not install stress distribution plates from one manufacturer with another manufacturer s fastener unless the combination is FM Approved Fasteners must be driven perpendicular to the deck to be effective. Particular caution is needed with tapered insulations Use the manufacturer s proprietary installation tool. A less desirable option is a properly adjusted screw gun, having a depth-sensing clutch, to avoid over-driving or under-driving screw-type fasteners Recommended Fastener Embedment: Sructural concrete: 1to1 1 2 in. (25-38 mm), Wood decks: Minimum 1 in. (25 mm). Note: For 3 4 in. (19 mm) thick plywood deck, approximately 1 4 in. (6 mm) of the screw will protrude through the deck underside. Steel deck: For screw-type fasteners in new construction, use the shortest screw that is at least 3 4 in. (19 mm) longer than the assembly being secured. Ensure fasteners engage the deck top flange. For recover steel deck construction, the fastener must be long enough to be driven through the existing roof system and into the deck at least 3 4 in. (19 mm). While top flange engagement is recommended in all cases, for recover construction, it is acceptable for insulation fasteners to engage the bottom flange of the deck. Ensure fasteners securing mechanically attached roof covers engage the top flange of the deck in all constructions. For other deck types: Follow the FM Approval requirements and manufacturers specifications Ensure insulation fastener placement is per Figures 3, 4, 5, and 6. If a particular insulation has a different required FM Approved fastener pattern, use that. Each fastener must engage the intended deck flange. This results in a spacing tolerance of approximately ± 1.5 in. (± 38 mm) for wide-rib deck if the edge of the board was at the centerline of the deck top flange. For smooth decks, such as plywood or concrete and steel deck in the direction of deck ribs, a maximum tolerance of ± 1.5 in. (± 38 mm) is acceptable.

13 Roof Deck Securement and Above-Deck Roof Components 1-29 FM Global Property Loss Prevention Data Sheets Page 13 Fig. 3. Fastener placement 2 4 ft( m) boards.

14 Page 14 FM Global Property Loss Prevention Data Sheets Fig. 4. Fastener placement 3 4 ft ( m) boards.

15 Roof Deck Securement and Above-Deck Roof Components 1-29 FM Global Property Loss Prevention Data Sheets Page 15 Fig. 5. Fastener placement 4 4 ft ( m) boards.

16 Page 16 FM Global Property Loss Prevention Data Sheets Fig. 6. Fastener placement 4 8 ft ( m) boards. For fastening densities not shown, the following guidelines apply: Ensure edge fasteners are 6 in. (152 mm) from the board edges, with tolerance as above. Ensure fasteners are evenly distributed over the board area. Ensure all fasteners engage the top flange of steel deck. (See note for recover construction, section above.) Recover and Reroof ConstructionDesign and Installation Recommendations This section covers planned recover and reroof operations. For repairs after wind damage has occurred, refer to Data Sheet 1-30, Repair of Wind Damaged Roof Systems Reroof ConstructionRemoval and Replacement of Above-Deck Components Reroof construction is generally preferred to recover construction due to the potential for moisture damage with recover construction from existing wet insulation inadvertently left in place.

17 Roof Deck Securement and Above-Deck Roof Components 1-29 FM Global Property Loss Prevention Data Sheets Page When reroofing, inspect the existing deck securement and, if necessary, fasten the deck per Data Sheet 1-28, Wind Design, prior to installation of the above-deck components When reroofing over a steel deck where the original assembly had been adhered with asphalt, do one of the following: Use an insulation specifically FM Approved for reroofing; that allows up to 15 lb per square (72 kg/100 m 2 ) of asphalt to remain on the deck. Remove all asphalt from the deck and install a system FM Approved for new construction Recover ConstructionExisting Components Remain All recover recommendations and FM Approvals are based on the assumption that there is only one existing roof system. If more than one roof system is in place (building has already been recovered), use reroof construction If recover construction is considered, perform the following actions: Remove all wet materials prior to application of the new roof system, with wet insulation being replaced with dry material. Cut out blisters. Roof cover blistering or rusting deck may be an indication that the existing insulation is wet. When this is observed, take one of the following steps: Reroof, as opposed to recover. See section Conduct an infrared or nuclear examination to detect any high-moisture content. If moisture is detected with one of these nondestructive methods, confirm the results by cutting out 1 1ft ( m) samples or roof cores as needed to determine the extent of wet insulation Recovermechanically attached recover systems. If the existing construction is dry, an FM Approved recover system can be applied over it. Ensure the entire assembly (insulation, fasteners, and roof cover) is FM Approved in combination for recover construction on the particular deck Ensure the thickness of the recover system is within the FM Approval limits. Most systems are limited to a maximum 1 in. (25 mm) thick roof insulation. A greater thickness may affect the Class 1 fire rating of the completed system. Installation of an FM Approved Class 1 recover assembly over an existing Class 2 roof system will not upgrade the assembly to Class 1. However, it would be possible to upgrade the external fire resistance rating (E108) with the addition of an FM Approved roof cover system When brooming gravel from the roof, do not pile it in one area. This can overload structural members causing collapse Do not use recover constructions using additional plies adhered directly to an existing BUR unless the entire assembly is FM Approved. This would essentially result in a 6- or 7-ply BUR over the insulation (3- or 4-ply existing BUR plus 3 plies added), most likely creating a Class 2 roof assembly When reroofing or recovering over gypsum, cementitious wood fiber, or lightweight insulating concrete decks, verify fastener pull-out performance with field tests. Perform 5 pull-out tests per 50,000 ft 2 (4650 m 2 ) using FM Approved fastening or a minimum of 5 tests. Run additional tests if inconsistent results are obtained. On larger roofs, the number of tests above the minimum can be reduced if consistent results are obtained. Fastener spacing is calculated per section It is not necessary to run pull-out tests of fasteners FM Approved for installation in steel deck, structural concrete, nominal 3 4 in. (19 mm) plywood, or nominal 2 in. (51 mm) lumber decks, unless the condition of the deck is in question Structural Concrete, FM Approved Fiber Reinforced Cement and Lightweight Insulating Concrete (LWIC) Decks: Design and Installation Recommendations NOTE: also see section for LWIC and for Structural Concrete Decks When an FM Approved asphaltic adhesive or asphalt is used to secure components to these decks, prime the deck with an FM Approved primer at the FM Approved rate, or with an ASTM D-41 asphalt cut-back primer at 0.75 to 1.25 gal per square (3.0 to 5.1 L/10 m 2 ).

18 Page 18 FM Global Property Loss Prevention Data Sheets Single-Ply Membrane Covers and Multi-Ply covers with Mechanically Attached Base Sheets Loss experience has shown that even properly secured single-ply roof covers can be damaged by windborne debris such as metal panels and broken glass. In areas prone to hurricanes, typhoons and tropical cyclones (see DS 1-28), use more durable roof covers. This would include multi-ply roof covers or single-ply membranes that are considerably thicker than the FM Approved minimum. Many single-ply membranes are manufactured in thicknesses up to to in. vs. the minimum FM Approved thickness of to in General Single-ply membranes can deteriorate when exposed to certain materials commonly discharged onto the roof. Also separate these membranes from incompatible substrate materials. In particular, ensure single-ply membranes do not come into contact with asphalt or coal tar-based materials. Ensure EPDM membranes are not exposed to gasoline, oil, solvents, or animal fats. Ensure PVC membranes are not in direct contact with EPS. Follow the manufacturer s recommendations for protection or separation Some FM Approved single-ply membranes are formulated with fire retardants on the top side only. Install these systems with that surface up. Membranes with this requirement are labeled on the underside THIS SIDE DOWN/IN Mechanically Attached Single-ply Membranes and Multi-Ply Covers with Mechanically Attached Base Sheets: Design Recommendations In the roof corners and perimeter, ensure the distance between rows of roof cover fasteners or batten bars are the following maximum percentages of the FM Approved spacing. Use the reduced spacing in all FM Approval classifications: Roof Perimeter: Distance between rows is 60% of the FM Approved roof field spacing, or one row of intermediate fasteners is provided in between. Roof Corners: Distance between rows is 40% of the FM Approved roof field spacing or two rows of intermediate fasteners are provided in between. An alternative for Class 1-90 and below (on steel deck) is to install perimeter fastener rows (60% of roof field as above) in both directions in the corners (any wind class acceptable for other types of decks). Refer to Figure 7. When the cover overlaps in the corner areas, install these fasteners from above the uppermost cover layer. For single-plies fastened along the side laps: Increased fastening density for single-ply membranes is often obtained by using narrower sheets. For single-ply membranes or base sheets, intermediate rows of fasteners may be installed through the sheet with a cover strip or additional plies applied over the fasteners, in accordance with the manufacturer s instructions. Use one intermediate row in the perimeter and two intermediate rows in the corners. Fastening increase is not always obtained by increasing the number of fasteners along each row, unless substantiated by FM Approval test data or otherwise done to provide a more practical spacing and distribution of wind loads. In some cases, such as over wood decks (see ) or LWIC, or with mod bit base sheets in high wind areas, enhanced securement for base sheets is provided by reducing the fastener spacing within and between rows in order to provide a uniform distribution (see section for examples). When steel deck is used, the fastener spacing across the deck ribs must be in even multiples of the deck rib spacing (6 in. or 150 mm for in. or 38 mm deep deck) to ensure the fastener engages the top deck flange. See Example 1. For point-attached membranes: Increased fastening density is obtained by decreasing the spacing between fastener points in one or both directions. Ensure total tributary area to each fastener is no more than 60% and 40% in the perimeter and corners, respectively, of the FM Approved roof field spacing. See Example 2. Example 1: A batten-attached system with FM Approved fastener spacing for Class 1-60 of rows 6 ft (1.8 m) on center and screws 6 in. (152 mm) on center would use 3.6 ft (1.1 m) maximum on center row spacing, with 6 in. (152 mm) on-center screw spacing in the perimeter and 2.4 ft (0.7 m) maximum on-center row spacing with 6 in. (152 mm) on-center screw spacing in the corners. In this case, rows of roof cover fasteners should extend across the deck ribs in all areas to properly distribute the load to points of deck securement. Since the needed wind uplift rating is limited, an option would be to use row spacing of 3 ft (0.9 m) maximum in both directions in the corners per Figure 7, and

19 Roof Deck Securement and Above-Deck Roof Components 1-29 FM Global Property Loss Prevention Data Sheets Page 19 Notes: 1. Fastener spacing along all rows is the same as field spacing. 2. See section for restrictions on fastener rows parallel to steel deck ribs. 3. If two layers of membrane are installed in the corner areas, all fasteners must secure the top layer. Fig. 7. Alternate corner increase for mechanically attached single-ply membranes. Note: Fastener spacing along all rows is the same as field spacing.

20 Page 20 FM Global Property Loss Prevention Data Sheets Example 2: A point-attached system with FM Approved fastener spacing for Class 1-90 of in. ( mm) could use a spacing of in. ( mm) in the perimeter. A in. ( mm) spacing may be needed for steel deck applications depending on deck rib direction. A spacing of in. ( mm) in the corners could be used. A in. ( mm) may be needed for steel deck applications depending on deck rib direction Mechanically Attached Single-Ply Membranes and Multi-Ply Covers with Mechanically Attached Base PliesInstallation Recommendations Ensure all roof cover fasteners engage the top flanges of steel deck Install batten bars and fastener rows perpendicular to steel deck ribs. Exception: for Class 1-75 and below, fastener rows and batten bars can be installed parallel to the building edge within the defined building perimeter width if: a) the distance between fastener rows in this area is 3 ft (0.9 m), and b) two FM Approved deck fasteners or minimum 5 8 in. (16 mm) diameter welds are installed through each lower deck flange (every 6 in., 150 mm on center) Where acceptable to the roof cover manufacturer, in lieu of seaming numerous partial single-ply membrane sheets in the rake areas, an FM Approved batten bar may extend across the perimeter width, midway between rows of fasteners and be fastened to the deck. Adhere a membrane strip of a minimum width as recommended by the manufacturer over the batten bar and the edges caulked to maintain water-tightness, if needed. Similar enhancements may be provided in the corner areas using two intermediate batten bars Provide deck securement as follows when the FM Approved (field-of-roof) spacing between rows of roof cover fasteners exceeds 6 ft (1.8 m): a) Use only FM Approved deck fasteners to secure the deck. Ensure the spacing within rows of deck fasteners in the field-of-roof does not exceed the spacing within rows of roof cover fasteners. b) Double the deck fastening in the roof perimeter. For example, if roof cover fasteners are 12 in. (300 mm) on center in the field, provide deck fasteners 12 in. on center in the field (per a.) and provide deck fasteners at 6 in. (150 mm) centers in the perimeter. If cover fasteners are 6 in. (150 mm) on center in the field, provide deck fasteners at 6 in. centers in the field (per a.) and provide two deck fasteners at 6 in. (150 mm) centers in the perimeter. c) In corner areas, use the same number of deck fasteners as for the perimeter, but with ¾ in. diameter washers. Ensure washers are carbon steel with a in. (8.4 mm) center hole and are minimum in. (1.6 mm) thick Ballasted Single-Ply Membrane: Design Recommendations Do not use stone-ballasted roofs on buildings taller than 150 ft (46 m) high, or in areas with design wind speeds 100 mph (45 m/s) (See Data Sheet 1-28, Wind Design) or beyond the acceptable limits of Tables 2 or 3. These limitations do not apply to paver ballasted systems To ensure the quality of the materials, component compatibility, and Class 1 undeside fire exposure ratings, ensure individual components in ballasted systems are FM Approved for use in combination. Typically, the combination would be FM Approved for adhered or mechanically attached applications. Use only FM Approved membranes in ballasted applications Ensure stone ballast in loose-laid systems is clean, smooth, well-rounded gravel meeting the gradation requirements of Standard Size No. 3 for Coarse Aggregate per ASTM D448 (nominal 1 to 2 in. [25 to 50 mm] diameter) Ensure the density of stone ballast is approximately 165 pcf (2650 kg/m 3 ). Do not use lightweight stone such as limestone Apply stone ballast per Table 2 or 3. Install paver blocks per Tables 4 to 7. Ensure square edge pavers are a minimum of 1 ft 2 (0.1 m 2 ). Ensure beveled/strapped pavers are a minimum of 0.89 ft 2 (0.08 m 2 ) (8 16 in., [ mm]). All weights are the minimum recommended weights.

21 Roof Deck Securement and Above-Deck Roof Components 1-29 FM Global Property Loss Prevention Data Sheets Page For ballast application only, the roof perimeter and corners are subject to a minimum dimension of 8.5 ft (2.6 m) rather than 4 ft (1.2 m) as defined in Data Sheet 1-28, Wind Design. Also, the 10% lesser building plan dimension limit is not applied in determining the corner dimension. The 4 ft (1.2 m) minimum and the 10% limit still apply to roof deck securement The structure must be capable of supporting the dead weight of the roof system and ballast without encroaching on live load capacity or creating or aggravating a ponding problem. Have the load capacity of the roof verified by a registered civil or structural engineer The roof slope should be 10, 2 in./ft (167 mm/m) Stone ballast can be used in the roof field with pavers used at the perimeter and corners, provided the appropriate weights of stone and pavers are used in each area Ensure flashing systems used with pavers secure the pavers at the building edge Ballasted Single-Ply MembraneInstallation Recommendation Extreme care is needed when transporting ballast to the roof. Stop the conveying machine if ballast begins to pile up. Distribute ballast to the specified weight before restarting the conveying machine Ballasted Single-Ply MembraneMaintenance Recommendation Inspect ballasted roofs semi-annually and after storms. Redistribute scoured ballast. Gravel scour greater than 50 ft 2 (5 m 2 ) is considered excessive. See Data Sheet 1-30, Repair of Wind Damaged Roof Systems, for action to be taken if this type of damage occurs. Table 2. Weight Needed of No. 3 Round Stone Ballast, Parapet 36 in. (914 mm) Uplift Pressure Ballast Weight, (psf) (psf) Data Steel or Pre-Cast Panel Deck Cementitious Wet Fill Deck Sheet 1-28 Field Peri. Cors. Field Peri. Cors to to to 35 Use FM Approved 1-90 System to 45 Use FM Approved 1-90 System Use FM Approved 1-90 System Table 3. Weight Needed of No. 3 Round Stone Ballast, Parapet > 36 in. (914 mm) Uplift Pressure Ballast Weight, psf (psf) Data Steel or Pre-Cast Panel Deck Cementitious Wet Fill Deck Sheet 1-28 Field Peri. Cors. Field Peri. Cors to to to to 45 Use FM Approved 1-90 System Table 4. Weight Needed of Paver Blocksnot T&G, Beveled or Strapped to Each Other, Parapet 36 in. (914 mm) Uplift Pressure Paver Weight, psf (psf) Data Steel or Pre-Cast Panel Deck Cementitious Wet Fill Deck Sheet 1-28 Field Peri. Cors. Field Peri. Cors to to to to 35 Use FM Approved 1-90 System to 45 Use FM Approved 1-90 System Use FM Approved 1-90 System

22 Page 22 FM Global Property Loss Prevention Data Sheets Table 5. Weight Needed of Paver Blocksnot T&G, Beveled or Strapped to Each Other, Parapet > 36 in. (914 mm). Uplift Pressure Paver Weight, psf (psf) Data Steel or Pre-Cast Panel Deck Cementitious Wet Fill Deck Sheet 1-28 Field Peri. Cors. Field Peri. Cors to to to to 35 Use FM Approved 1-90 System to 45 Use FM Approved 1-90 System Use FM Approved 1-90 System Table 6. Weight Needed of Paver BlocksT&G, Beveled or Strapped to Each Other, Parapet 36 in. (914 mm) Uplift Pressure Paver Weight, psf (psf) Data Steel or Pre-Cast Panel Deck Cementitious Wet Fill Deck Sheet 1-28 Field Peri. Cors. Field Peri. Cors to to to to to 40 Use FM Approved 1-90 System Table 7. Weight Needed of Paver BlocksT&G Beveled or Strapped to Each Other, Parapet > 36 in. (914 mm) Uplift Pressure Paver Weight (psf) (psf) Data Steel or Pre-Cast Panel Deck Cementitious Wet Fill Deck Sheet 1-28 Field Peri. Cors. Field Peri. Cors to to to to to Notes: 1. For all tables, to convert to kg/m 2, multiply by Uplift pressure is that determined from Data Sheet 1-28, Wind Design, and is not factored Asphalt and BUR Installation Recommendations Locate heating kettles so that buildings and combustibles will not be exposed Apply asphalt at the equiviscous temperature (EVT) ± 25 F (± 14 C). Ensure asphalt is not continuously heated to or above the blowing temperature. These temperature limits are generally supplied by the manufacturer Immediately roll felt into the asphalt. If the roll veers off line, cut it and start again. Broom organic felts in place Keep rolls of felts dry and store on end Roof Covers Adhered to Mechanically Attached Base SheetsFastener Installation Recommendations Increase the number of fasteners securing the base sheet over the FM Approved roof field spacing by 70% in the perimeter and 160% in the corners. For mod bit base plies secured to steel deck roofs, see recommendation For other deck types and uniformly reinforced base plies, determine fastening density on a unit area per fastener basis.

23 Roof Deck Securement and Above-Deck Roof Components 1-29 FM Global Property Loss Prevention Data Sheets Page Ensure fasteners for lightweight insulating concrete are not closer than 4 in. (102 mm) on-center, to avoid cracking the deck For base sheets only, fastening increases can be obtained by adding rows of fasteners and/or additional fasteners along each row Liquid Applied Roof CoversInstallation Recommendations At the end of each work day, spray-in-place polyurethane must be protected with the coating. At a minimum, apply the base coat at the end of each day. The foam will be degraded by UV radiation without the coating Ensure the roof surface is clean and dry prior to applying polyurethane foam or coating Mechanically Fastened Base Sheet Assemblies Over Wood DecksDesign and Installation Recommendations Currently, there are no FM Approved combinations of a base sheet mechanically fastened directly to a wood deck followed by a BUR or modified bitumen cover. These assemblies are popular in some regions. They are considered Class 2 and need automatic sprinkler protection regardless of the FM Approval status of the deck. They can be acceptable from a wind resistance viewpoint if installed in accordance with this section. Field of Uplift Pressure (Data Sheet 1-28 Table 8. Base Sheet Fastener Coverage for Non-FM Approved Combinations, ft 2 per Fastener < 21 psf (< 1.0 kpa) psf ( kpa) psf kpa) Roof Area Field Peri. Cors. Field Peri. Cors. Field Peri. Cors. Fastener Strength, lb(n) 30(135) 40(180) 50(220) 60(265) 70(310) 80(355) 90(400) 100(445) 110(490) 120(535) 140(625) 160(710) To convert to m 2 per fastener, multiply by When coverage is less than 0.50, a stronger fastener is suggested. Ensure coverage does not exceed 2.00 unless FM Approved. 3. Less than 40 lb (180 N) pull-out per fastener may indicate unsound deck or improper fastener. Consult manufacturer s specifications. 4. If the building has a minimum 3 ft (0.9 m) high continuous parapet and the roof slope is 10 (167 mm/m), the corner areas may be fastened in the same manner as the perimeter

24 Page 24 FM Global Property Loss Prevention Data Sheets Table 9. Standard 36 in. (0.9 m) Base Sheet Fastening (Non-FM Approved Components). (See Fig. 8.) Fastener Coverage, ft 2 /fastener (Table 8) Maximum Fastener Spacing, in. (mm) On Center One Intermediate Row Two Intermediate Rows At Laps Between Laps At Laps Between Laps 4 (102) 5 (127) 6 (152) 8 (203) 10 (254) 12 (305) 12 (305) 12 (305) 12 (305) 12 (305) 7 (179) 12 (305) 14 (356) 14 (356) 14 (356) 16 (406) 20 (508) 24 (609) 24 (609) 24 (609) 4 (102) 5 (127) 7 (179) 8 (203) 10 (254) 12 (305) 12 (305) 6 (179) 11 (279) 13 (330) 16 (406) 20 (508) 22 (559) 22 (609) Fig. 8. Fastener layout for 36 in. (914 mm) wide base sheet.

25 Roof Deck Securement and Above-Deck Roof Components 1-29 FM Global Property Loss Prevention Data Sheets Page 25 Table 10. Minimum Metal Disk or Fastener Head Size (Base Sheet Fasteners) Fastener Pull-Out Strength, lb (N) < 45 (200) ( ) ( ) ( ) ( ) ( ) > 120 (535) Minimum Disk/Head Diameter, in. (mm) 1.00 (25) 1.25 (32) 1.50 (38) 1.75 (44) 2.00 (51) 2.50 (64) 3.00 (76) Perform field pull-out tests of the proposed base sheet fastener to determine pull-out performance. Base sheet fastener spacing and head or disk size is then determined per Tables 8, 9, and 10. An example calculation is given below Ensure base sheet fasteners have metal heads or disks Where non-fm Approved wood roof decks have been used and an FM Approved roof system (above-deck components) is installed, roof system fastening can be in accordance with the Approval Guide listings for FR-treated wood decks, provided the deck is nominal 3 4 in. (19 mm) thick plywood or nominal 2 in. (51 mm) thick lumber. If a thinner deck is used, fastener pull-out tests are needed. Determine the fastener density per section Example Problem: Wood Deck, Nailed Base Sheet: Given: The field-of-roof uplift pressure (See Data Sheet 1-28, Wind Design) is 28 psf (1.35 kpa) and the fastener pull-out strength is 120 lb (535 N). From Table 8, 10th line (120 lb, 535 N), select maximum coverage area per fastener as follows: Roof field = 2.00 ft 2 (0.2 m 2 ) Roof perimeter = 1.14 ft 2 (0.1 m 2 ) Roof corners = 0.77 ft 2 (0.07 m 2 ) From Table 9, select base sheet fastener spacing: Area At Laps Between Laps Roof field 12 in. (305 mm) 20 in. (508 mm) Perimeters 8 in. (203 mm) 14 in. (356 mm) Corners 5 in. (127 mm) 12 in. (305 mm) Per Table 10, the fastener head or disk size needs to be at least 2.5 in. (64 mm) in diameter Roof Deck Span and Securement for Wind Loads Design Recommendations Use FM Approved steel deck for all insulated steel deck roofs. Do not use the deck at spans greater than FM Approved. The FM Approved spans are measured center-to-center. For new construction, ensure the deck span is adequate for wind pressures in all roof areas, including the perimeter and corner areas (see DS 1-28 and examples in section ), taking into consideration the following (unless specifically tested and FM Approved): For roofs with proposed spans and wind design pressures exceeding Table 11, or where a large spacing between rows of fasteners for mechanically fastened roof covers results in large concentrated loads (as noted below or defined by the RoofNav listing), this may necessitate the use of steel deck with higher yield strength or spans less than the FM Approved maximum limit as noted below may be necessary. Use Grade 80 (F Y = 80,000 psi), wide rib, minimum 22 ga. ( in., mm) steel deck with a maximum span of 6 ft (1.8 m) when roof systems need an FM Approval rating higher than 1-90, or when the spacing between rows of roof cover fasteners is greater than 6 ft (1.8 m). When the FM Approval rating needed for the field of the roof is higher than 1-135, use minimum 22 ga. ( in., mm), Grade 80 (F Y = 80,000 psi), wide rib steel deck. Also, in corner areas, either use spans less than 6 ft (1.8 m), or 20 ga. ( in., mm) or 18 ga. ( in., mm) deck as needed per Table 11 and as adjusted to reflect the higher grade of steel.

26 Page 26 FM Global Property Loss Prevention Data Sheets Use Table 11 to ensure the allowable wind uplift pressure resistance of the deck is not exceeded. Use enhanced deck securement for areas with higher wind design pressures as defined by Span Type Table 11. Allowable 2 Uniform Uplift Pressure ALLOWABLE UNIFORM UPLIFT PRESSURE (psf) FOR GRADE 33 (Fy = 33,000 psi) STEEL ROOF DECK 1.5 Type B WIDE RIB (WR) Gage SPAN SINGLE DOUBLE TRIPLE Span Type Gage 1.5 Type F- INTERMEDIATE RIB (IR) SPAN SINGLE DOUBLE THREE OR MORE SPAN TYPE Gage 1.5 Type A NARROW RIB (NR) SPAN SINGLE DOUBLE THREE OR MORE

27 Roof Deck Securement and Above-Deck Roof Components 1-29 FM Global Property Loss Prevention Data Sheets Page 27 ALLOWABLE UNIFORM UPLIFT PRESSURE (psf) FOR GRADE 33 (Fy = 33,000 psi) STEEL ROOF DECK 3 Type N DEEP RIB (3DR) SPAN TYPE Gage SPAN SINGLE DOUBLE THREE OR MORE Notes for Table 11: 1. This table includes a 1 3 increase in normal allowable stress. It should be used specifically for wind and should not be used to determine gravity load resistance. 2. Compare the values in this table to design pressures per DS Do not apply a safety factor to the design pressures as one is included in this table. 3. Table 11 is based on a yield stress (Fy) of 33,000 psi. For higher strength steels the allowable wind uplift pressure may be determined by multiplying the values in Table 11 by 1.15 when Fy = 40,000 psi (276 mpa), by 1.35 when Fy = 50,000 psi (345 mpa) and by 1.55 when Fy 60,000 psi (415 mpa). These multipliers take into consideration both the increase in strength due to Fy and the decrease in strength due to deformation at higher stresses, so the relationship between yield strength and allowable pressure is not linear. 4. Interpolation by proportioning the square of the spans is most accurate; however, linear interpolation is reasonably accurate for these span increments. 5. Where the recommended deck design pressure exceeds the capacity shown in Table 11, assemblies in which the combination of above-deck components and securement act compositely with the deck may be accepted provided they have been satisfactorily tested. In addition to the recommendations below, for mechanically attached single-ply membranes and multi-ply covers with mechanically attached base sheets, also refer to section Secure steel deck to supports for Class 1-90 and below, (unfactored design pressure 45 psf) as follows: Space FM Approved deck fasteners or welds a maximum of 12 in. (305 mm) on center (every other rib for in. [38 mm] deck) at all supports in the field of the roof. Space FM Approved deck fasteners or welds a maximum of 6 in. (152 mm) on center (every rib for in. [38 mm] deck) at all supports in the roof corners and perimeter. For Class 1-75 and 1-90 (field rated) construction, use FM Approved deck fasteners or minimum 5 8 in. (16 mm) diameter welds in the field and perimeter; and use either one FM Approved deck fastener or two welds in each rib in the corner area. For Class 1-60 (field rated) construction, use FM Approved deck fasteners or minimum 1 2 in. (13 mm) diameter welds in the field and perimeter, and use FM Approved deck fasteners or minimum 5 8 in. (16 mm) diameter welds in the corners. Secure the deck to supporting members at each deck side lap, regardless of resultant weld spacing. For interlocking-type side laps (Fig. 9a), secure both sides of the lap (upper and lower). For overlap-type side laps (Fig. 9b), ensure securement penetrates all deck panels at the laps When Steel Deck Institute (SDI) deck-weld patterns are specified for use with in. (38 mm) deck, 24/3 or 36/4 patterns are acceptable where a maximum 12 in. (300 mm) weld spacing is recommended and 24/5, 24/7, 30/6, 30/8, 36/7 or 36/9 patterns are acceptable where a maximum 6 in. (150 mm) weld spacing is recommended.

28 Page 28 FM Global Property Loss Prevention Data Sheets Fig. 9a. Side lap fastening: interlocking seam. Fig. 9b. Side lap fastening: overlap seam If the recommended field of roof wind rating exceeds Class 1-90 (unfactored design pressure > 45 psf), or if the FM Approved field-of-roof deck fastening requires fasteners/welds at every rib, secure each rib in the field of the roof. For corner and perimeter areas, enhance deck securement using one or more of the following: Two FM Approved deck fasteners per rib (see Fig. 10) Shorter spans, yielding an equivalent increased fastening density Use 3 4 in. (19 mm) diameter, (0.328 in. [8.4 mm] diameter center hole; in. [1.6 mm] minimum thickness), carbon steel washers with deck fasteners in corner areas whenever the recommended field of roof rating exceeds 1-135, or when the combination of needed wind rating and roof cover fastener row spacing for mechanically fastened single plies (MFSP) warrants it. When this method is used, and the thickness of the steel purlin is less than 1 8 in. (3.5 mm) the designer should ensure fastener pullout resistance from the purlin is not exceeded. See Section for an example Provide mechanical fastening at all deck side laps as follows, unless the specific FM Approval listing requires a closer spacing: Class 1-90 or lower: Ensure spacing between each side lap fastener or side lap fasteners and supports is no more than 36 in. (0.9 m) in the field of the roof and no more than 30 in. (0.76 m) on center in the perimeter and corner areas. Class through 1-120: Ensure side lap fastening is no more than 30 in. (0.76 m) on center in the field of the roof, and no more than 15 in. (0.38 m) on center in the perimeter and corners. Class and higher: ensure side lap fastening is no more than 24 in. (0.61 m) on center in the field of the roof, and no more than 15 in. (0.38 m) on center in the perimeter and corners. Fasten overlap-type side laps with FM Approved side lap fasteners. Interlocking-type laps can be fastened by button punching in Class 1-90 and lower. Do not weld side laps Ensure steel deck end laps are a minimum of 2 in. (51 mm). No additional fastening over that noted above is needed for end laps. Consider specifying wider (4 in., 102 mm) end laps in the design. This will make proper field installation easier by compensating for manufacturing and construction tolerances.

29 Roof Deck Securement and Above-Deck Roof Components 1-29 FM Global Property Loss Prevention Data Sheets Page 29 Fig. 10. Two deck fasteners per support, one into each bar joist top flange For new construction, the structural design engineer of record is responsible for determining if more stringent design criteria is needed with regard to the deck type and securement, such as providing design diaphragm resistance in conjunction with wind uplift resistance Installation Recommendations Place steel deck true and straight so edges of insulation boards will not gradually move off the deck flanges as the boards are installed Ensure workers stand on the upper deck panel when fastening laps, otherwise permanent deflection can occur. See Figures 9a and 9b Lightweight Insulating Concrete Roof Decks Design Recommendations When a lightweight insulating concrete (LWIC) roof assembly is to be used as part of a new roof or re-roof in non-hurricane prone regions, ensure it is FM Approved for the specific wind pressure recommended in the field of the roof, with prescriptive enhancements provided for the securement of base sheets in the perimeter and corner areas in accordance with recommendation For regions prone to hurricanes, typhoons and tropical cyclones, ensure the entire LWIC system is FM Approved for the specific wind pressure rating needed for the field, perimeter, and corner areas as noted in Table Ensure form deck securement is as follows: For FM Approved installations using 1.5 in. (38 mm) deep steel deck as the form deck, ensure it is FM Approved steel deck, designed and installed in accordance with the Approval Guide listing, FM Approvals RoofNav, and section

30 Page 30 FM Global Property Loss Prevention Data Sheets For installations using different form-deck profiles, ensure the deck is secured in the field of the roof in accordance with the FM Approvals RoofNav listing. If form deck perimeter and corner fastener density is not specified in the FM Approvals RoofNav then ensure it is in accordance with section In addition, for roof corners in all construction and roof perimeters in Class 1-75 and above, ensure the maximum distance between welds or fasteners at each supporting member is 4 in. (102 mm), regardless of the load per weld Ensure all welding on deck less than 22 ga. ( in., mm) incorporates minimum 3 8 in. (9.5 mm) hole weld washers Ensure all form decks are of galvanized steel. Do not use aluminum alloy coatings Provide mechanical fastening at all form deck side laps. Ensure side lap fastener spacing is in accordance with section Installation Recommendation When installing lightweight insulating concrete on the form deck, the thickness of the initial slurry, prior to placing the expanded polystyrene (EPS) insulation, is critical. There must be sufficient lightweight insulating concrete to ensure an adequate bond. Refer to the FM Approvals RoofNav Ensure the following is done in regions prone to hurricanes, typhoons, and tropical cyclones: a) Have a waste container at the job site. Initial flow of LWIC should be into the waste container until it is flowing properly and is free of excess water. b) Pour samples for wet density, dry density, and compression tests just prior to pouring the actual LWIC deck. Compare wet density results to manufacturer s data immediately, and compare other test results later when they become available. c) For mechanically fastened (MF) base sheets, conduct pull-out tests on base sheet fasteners after the deck has set (2-3 days), but just before the base sheet is secured Ensure fasteners driven into lightweight insulating concrete are not closer than 4 in. (102 mm) on center, to avoid cracking the deck Cementitious Wood Fiber Roof Deck Recommendations Ensure deck securement in the field of the roof is in accordance with the RoofNav listing For decks that are through-fastened to supports, increase the number of fasteners securing the deck in the perimeter and corners in accordance with, section For decks secured with clips at the side laps, use one of the following methods to increase fastening at the corner and perimeter areas: The number of clips can be increased in accordance with section by installing additional supports to accommodate the additional clips. Additional securement can be obtained by installing through-fasteners in the corners and perimeter in accordance with section above. Determine the number of additional fasteners assuming the deck was secured with these fasteners in the field of the roof Lumber and Plywood Deck Recommendations Use FM Approved fire-retardant (FR) treated lumber and plywood for all new wood roof deck construction. FM Approved lumber is minimum 1.5 in. (38 mm) thick (nominal 2 in. [51 mm]) and FM Approved plywood is minimum 23/32 in. (18 mm) thick (nominal 3 4 in. [19 mm]) Where non-fm Approved wood roof decks have been used, roof deck fastening to resist anticipated wind loads can be as outlined below.

31 Roof Deck Securement and Above-Deck Roof Components 1-29 FM Global Property Loss Prevention Data Sheets Page 31 Note: If the deck is thinner than the minimum FM Approved thicknesses, above-deck fastener pullout tests are needed, as all above-deck fastening Approvals are based on the minimum FM Approved thickness. Refer to section for details on fastener pullout tests. In no case should plywood roof deck be thinner than in. (15 mm) [nominal 5 8 in. (16 mm)] Above-deck components on wood decks are currently FM Approved only for up to Class Hence, deck fastening recommendations are for these uplift ratings only Ensure plywood fastening is as follows: Deck panels are staggered in one direction. Fastening is based on 2 ft (0.6 m) span, with panel ends supported. Refer to RoofNav for guidance on FM Approved plywood deck fasteners. Where not available nail per guidelines below. For nominal 5 8 in. (16 mm) thick deck, minimum 8d nails are used. For thicker decks, minimum 10d nails are used. Smooth shank nails are acceptable for all fastening except roof corners in Class 1-75 and 1-90, where ring shank nails are needed. For Class 1-60, field-of-roof nails are installed 6 in. (152 mm) on center at plywood panel end supports, and 12 in. (304 mm) on center at all intermediate supports. For Class 1-60 perimeter and corners, and Class 1-75 and 1-90 across the entire roof, nails are installed 6 in. (152 mm) on center at all supports Ensure nominal 2 in. (51 mm) lumber fastening is as follows: Determine the design wind load and multiply by the tributary area of the nail, to determine the design load on the nail. Determine nail penetration into support. Determine nail pullout strength by multiplying penetration length by appropriate value in Table 12 below. Table 12. Nail pullout strength per in. (25 mm) of penetration Nail Size (pennyweight) Pullout Resistance per in. (25 mm) of embedment, lb (N) 12d 28 (125) 16d 31 (138) 20d 36 (160) 30d 39 (173) Ensure pullout strength is at least twice the design load for the nail. Increase fastening at the roof perimeter and corners per section Structural Concrete Roof Deck Recommendations Cast-in-place and precast structural concrete decks are acceptable in all wind exposures provided the appropriate above-deck system is used (See Table 1). Use assemblies that are FM Approved over concrete deck with wind uplift pressure ratings adequate for all areas including the perimeter and corners. For roof systems using mechanically fastened insulation, see Ensure securement of precast structural concrete panels is designed by a professional civil or structural engineer (PE). Deduct no more than 90% of the dead weight of the panels when calculating the fastening needed for wind uplift resistance Torch Application of Modified Bitumen Roof Covers Safely install torch-applied roof covers to prevent ignition of the roof assembly. Follow guidelines in FM Global DS 1-33, Safeguard Torch-Applied Roof Installations Install torch-applied covers properly to ensure adequate adhesion and wind uplift resistance. Consider the following where practical and safe:

32 Page 32 FM Global Property Loss Prevention Data Sheets a) The torch applicator should face the leading edge of the roll and pull the roll toward them. Walking behind the roll and pushing the roll results in an improper angle for torch flame impingement onto the roll, and results in damage to the cover from walking on the heated and softened sheet layer. b) Pass the torch flame back and forth across the leading edge of the roll, with most of the flame impinging on the leading edge of the roll, and only slight heating of the substrate below. c) Do not overheat the roll, such as to cause excessive smoke. d) Allow the bitumen to pool slightly at the leading edge of the roll across its entire width, allowing the pool to flow very slightly beyond the edge of the roll as the sheet is unrolled (see Fig. 11). Fig. 11. Torch application of upper ply to a mechanically fastened base sheet Note adhesive pooling at the leading edge of the roll Field Wind Uplift Tests Conduct field uplift tests at FM Global insured client locations where practical, on all new, re-roofed or re-covered roof installations in hurricane-prone regions where the basic wind speed is at least 100 mph (45 m/s), except where otherwise noted in DS 1-52, Field Uplift Tests. Conduct tests in accordance with DS Cold-Process Adhesives Plan roof installations in locations that are prone to hurricanes or tropical cyclones and that use cold-process adhesives to allow adequate curing time prior to potential exposure from a tropical cyclone. Also, see section Fiberglass Reinforced Plastic (FRP) Roof Deck Recommendations Ensure the deck is secured in the field of the roof in accordance with the FM Approvals RoofNav listing.

33 Roof Deck Securement and Above-Deck Roof Components 1-29 FM Global Property Loss Prevention Data Sheets Page If deck perimeter and corner fastener density is not specified in the FM Approvals RoofNav, then ensure it is in accordance with section SUPPORT FOR RECOMMENDATIONS 3.1 Supplemental Information Class 1 and 2 Roof Decks In 1953, a serious fire occurred in which fire spread along the underside of the insulated steel roof deck of a large industrial facility. There were few combustibles in the building. The fire started at floor level and heated the underside of the deck. Hot gases (from combustible above-deck components) were forced down through the deck joints and became ignited. The fire continued to feed on the hot gases and spread along the underside of the roof throughout the building. The entire building and contents were lost. Such losses led to the development of the FM Approved Class 1 insulated steel deck roof, in which only insulations of relatively low combustibility, used with restricted quantities of adhesive, were recommended. As a result, fire losses from the burning of insulated steel deck roofs have decreased significantly. The use of mechanical fasteners, as opposed to adhesives, to secure materials to the deck, further decreases the fire hazard of newly constructed roofs. It should be noted that many Class 2 roofs are still in existence. Loss experience involving Class 2 insulated steel deck in recent years has been favorable because most are protected with sprinklers. While combustible gases are liberated from both Class 1 and 2 roof decks, there are sufficient combustibles only in Class 2 roof decks to produce a self-propagating fire across the roof underside. The fire propagates without additional heat input from the occupancy fire. This can result in complete destruction of the building contents. Sprinkler protection or an FM Approved roof deck undercoating is needed to prevent fire spread under Class 2 roofs. Class 2 steel deck roofs can be upgraded to Class 1 by one of two methods: (1) Remove all above-deck components, including asphalt, down to the deck and mechanically fasten a roof system that is FM Approved for new construction on the deck. (2) Apply an FM Approved roof deck undercoating to the entire steel deck underside. These coatings enable Class 2 roof decks to meet the heat release rate limits of Class 1 roofs. Under-coatings are only FM Approved and recommended for use on steel decks. If the combustibility of an existing roof deck is not known, a Class 1 or 2 rating can be determined by cutting out a sample for testing. For details, refer to Data Sheet 1-5, Removal and Shipping Roof Deck Samples for Calorimeter Testing Wind Uplift Resistance, Non-Ballasted Roof Covers Perimeter and Corner Enhancements for Mechanically Fastened, Multi-Ply Roof Covers For a mechanically attached roof ensure cover the spacing between rows of fasteners does not exceed 60% of the spacing (of that FM Approved for the field of roof [FOR] rating) in the perimeter and 40% in the corners. This accounts for the higher pressure coefficients in those areas (1/0.6 = 1.67, 1/0.4 = 2.5). From a practical standpoint, for a multi-ply cover that is FM Approved when fastened in or through the seams only, that would relate to adding one intermediate row of roof cover fasteners in the perimeter and two intermediate rows in the corners. Rows of fasteners should run across the deck ribs to evenly distribute the wind loads to points of deck securement. Spacing within rows can be the same throughout. When the FOR FM Approved system already has one intermediate row and the spacing is 12 in. (300 mm) in the seams and 12 in. (300 mm) in one staggered intermediate row. The average fastener spacing is about 1.5 ft 2 (0.14 m 2 ) for the field, and should be no more than 0.90 ft 2 (0.084) and 0.60 ft 2 (0.056 m 2 )inthe perimeter and corners, respectively. The spacing between fasteners in rows should be in multiples of 6 in. in order to hit the top flanges of in. (38 mm) deep steel deck. For the perimeter, the fasteners could be placed 6 in. (150 mm) OC in the seams and 6 in. (150 mm) OC in the intermediate row (0.75 ft 2, 0.07 m 2 ). For the corners, the fasteners could be placed 6 in. OC (150 mm) in the seams and 6 in. (150 mm) OC in two intermediate rows (0.50 ft 2 or 0.05 m 2 per fastener).

34 Page 34 FM Global Property Loss Prevention Data Sheets When the FM Approved system to be used in the field of the roof already requires one or more intermediate rows of roof cover fasteners, this becomes a little more complicated. If the FOR FM Approved system already has two intermediate rows and the Approved spacing is 12 in. (300 mm) in the seams and 18 in. (450 mm) in two staggered intermediate rows, the average fastener spacing is about 1.25 ft 2 (0.12 m 2 ) for the field, and should be not exceed 0.75 ft 2 (0.07 m 2 ) and 0.50 ft 2 (0.05 m 2 )in the perimeter and corners, respectively. The spacing between fasteners in rows should be in multiples of 6 in. (150 mm) in order to hit the top flanges of in. (38 mm) deep steel deck. For the perimeter, the fasteners could be placed 6 in. OC (150 mm) in the seams and 12 in. (300 mm) OC in two staggered intermediate rows, or 12 in. (300 mm) OC in the seams and in three staggered intermediate rows (0.75 ft 2 or 0.07 m 2 /fastener). If fasteners go thru both layers at the seam, then the latter alternative is recommended. For the corners, the fasteners should be placed 6 in. (150 mm) OC in the seams and 6 in. (150 mm) OC in two intermediate rows (0.50 ft 2 or 0.05 m 2 per fastener). An adhered roof covering obtains its uplift resistance from the tensile strength of the adhesive bond between the roof cover and insulation. When failure occurs, the result will be separation from the material below, or fractured insulation boards. Continuing uplift forces lead to peeling of the cover, which can result in the rapid delamination of large areas of the roof covering. FM Global research testing has shown that fastener placement on the insulation board has a significant effect on the ultimate strength of the assembly. For example, research conducted with 4 4ft 1.5 in. ( m 38 mm) polyisocyanurate insulation covered with a BUR showed a dramatic change in performance simply by rearranging the fasteners on the boards. For both tests, the fastening density was 1 fastener per 1.78 ft 2 (0.17 m 2 ). Figures 12a and 12b show the fastener placement for each test. Fig. 12a/12b. 4 4 ft ( m) insulation boards secured with nine fasteners per board. The test of pattern 12a failed at 105 psf (5.0 kpa) by fracture of the insulation board. The test of pattern 12b failed at 160 psf (7.6 kpa) by screws pulling out of the deck. Mechanically attached single-ply membranes are secured by fasteners that directly engage the deck. This results in a concentration of forces that are transmitted into the fastener. There also are high stresses in the membrane at the fastener. If one fastener fails, the load will be transferred to adjacent fasteners, usually causing these fasteners to be overstressed. If fasteners are driven into the bottom flange of steel deck, the moment arm is at least 1.5 in. (38 mm) longer (the depth of steel deck) than with top flange engagement. This longer moment arm can result in increased fastener back-out and failure Cold Process Adhesives in Tropical Cyclone Exposed Areas

35 Roof Deck Securement and Above-Deck Roof Components 1-29 FM Global Property Loss Prevention Data Sheets Page 35 The installation of roof systems in regions prone to hurricanes, typhoons, and tropical cyclones need to be completed in sufficient time for the adhesive to cure prior to exposure by these storms. While it is sometimes difficult to control installation schedules, every effort should be made to minimize the exposure. The start of hurricane season is June 1 north of the equator and November 1 south of the equator. Hurricane seasons last six months and the worst storms typically occur during the middle of the season. For some adhesive types used with multi-layer roof systems, a minimum of 28 days is required for curing. That is the maximum cure time allowed prior to lab testing. While local weather conditions can vary exact cure times, allowing 28 days helps to ensure the strength is comparable to that of the sample that was lab tested. Single-ply covers adhered with contact adhesive may be near full strength within about 7 days. Depending on local conditions, types of materials, and even the number of roof cover layers, some cold-process, multi-ply assemblies may continue to increase in strength for 60 days or more after the installation. Scheduling to avoid hurricane season also allows more time for curing prior to conducting field uplift tests, increasing the probability of success. Consult the roof material manufacturer regarding information relating to the percentage of ultimate strength for the assembly in question vs. cure time. In no case should an assembly be used where it may be exposed by a tropical storm before reaching at least 50% of its ultimate strength Wind Uplift Resistance, Ballasted Systems It is not possible to evaluate the uplift resistance of ballasted systems in the same manner as adhered coverings. The criterion for failure for the latter system is separation of the covering from the insulation, or the insulation from the deck. Ballasted systems fail these criteria by definition. Uplift forces are not uniform over the entire roof. Properly designed ballasted systems take advantage of the average uplift force in a given roof area. The membrane distributes the uplift force, allowing the ballast to be effectively utilized. Extreme winds, however, may cause gravel scour, paver dislodgement, and minor ballooning of the covering. The gravel will pile up around the edges of the ballooned area. The ridges of stone usually limit the scouring to a small area. Larger ballooned areas are expected when the roof deck has joints (steel, wood, precast panel, etc.) in it. When the deck is monolithic, very little air can flow up through the deck and act on the underside of the covering. In addition, a parapet at least 3 ft (0.9 m) high will help to reduce ballast scour Compatibility With Substrate When most single-ply membranes are used over existing asphaltic roofs, a layer of insulation or slip sheet is required to separate the single-ply membrane from the old surface. An exception is the use of some modified bitumen sheets that are FM Approved for direct application to asphalt BURs. There are other compatibility issues depending on the roof cover material and substrate, which is why only FM Approved combinations are recommended External Combustibility FM Approved roof covers are required to pass the ASTM E108 external fire test. During installation, unique fire hazards can occur with some single-ply membranes. Low flash point cleaning solvents and solvent-based adhesives can be ignited and are particularly hazardous when vapors are confined, such as at expansion joints. The installation of torch-applied membranes is an inherent fire hazard Recover Construction As recommended, remove all existing wet material from the existing roof system prior to reroofing. If only a small amount of existing material is wet, it would be acceptable to remove only the wet areas to the deck, replace the material with a properly secured insulation FM Approved for reroof or new construction on that deck, and then apply an FM Approved recover system over the entire roof. There is no preference for either removing all existing materials or only the wet materials, provided no wet materials remain. Roof vents are not considered effective in removing existing moisture. A maximum of one recover roof system is recommended, for the following reasons:

36 Page 36 FM Global Property Loss Prevention Data Sheets For other than noncombustible decks, if more than one recover system is installed, the roof would be considered Class 2. Additional recover systems increase the possibility of trapped moisture. Most building codes allow only one recover system Wind Uplift See Data Sheet 1-28 for determining the uplift pressure. DS 1-28 offers various optional design levels for winds that meet or exceed the basic design wind speed. The intent is to provide an increase in building performance for various incremental construction cost increases, and the guidance takes into consideration the likelihood of various failure modes occurring based on past experience. It is extremely important to recognize that wind blowing over a roof exerts varying uplift forces on different areas of the roof. For simplicity, the roof can be divided into three areas: (1) corners, (2) perimeter and (3) the field-of-roof (area inside corners and perimeter). The roof perimeter and corners are exposed to higher uplift forces than the field of the roof. The maximum uplift force occurs at the corners when the wind blows at an angle of about 45 to the roof (roughly along the diagonal). The maximum uplift force along the windward roof perimeter occurs when the wind blows at 90 to the perimeter. Actual pressure coefficients for the corners and perimeter vary, depending on the building height, parapet height, roof slope, etc. To compensate for these increased pressures, special roof deck and above-deck component fastening is recommended in the corner and perimeter areas. To provide adequate resistance for these higher wind pressure areas, one of the following can be done: 1. A roof system that is rated for that needed in the field, perimeter, and corner areas may be used. This could consist of the same system used throughout, or a system that is essentially the same throughout except that more fasteners are listed for the higher-rated version provided for the perimeter and corner areas. There are many FM Approved assemblies for use on concrete deck, and some assemblies for use on steel deck (with mechanically fastened covers or roofs adhered to dense cover boards), that are rated for several hundred psf. 2. A mechanically fastened cover may be used, with a reduced fastener row spacing in the perimeter and corner areas. 3. For relatively low wind-pressure designs, prescriptive enhancements may be used, consisting of providing additional insulation fasteners in the perimeter and corner areas for adhered roof covers. This approach has limitations as described below, but is acceptable where ONE of the following conditions is met: a) The NEEDED wind rating in the field of roof is 60 or 75 psf (3.6 kpa or less), OR b) The roof is in a non-hurricane prone region where the design wind speed does not exceed 90 mph (40 m/s) and the roof height does not exceed 75 ft (23 m) in Surface Roughness Exposure (SRE) B or C. For partially enclosed buildings in SRE D, roof height is limited to 30 ft (9.1 m). Except where otherwise noted, it is not necessary to actually calculate the increased pressure. The increased fastening recommended for these areas is sufficient to resist these forces. Prescriptive enhancements, such as providing additional insulation fasteners for adhered roof covers, will generally increase wind resistance. However, there is a practical limit to the additional wind resistance that can be achieved and the reduction in area per fastener. Insulation fastener spacings less than 1 ft 2 (1 per 0.1 m 2 ) become impractical and yield diminishing returns on wind uplift resistance, as ultimately the roof cover may peel off the insulation the roof insulation facer may delaminate or the insulation or cover board itself may delaminate. Even with a fastener spacing equal to or slightly greater than 1 ft 2 (1 per 0.1 m 2 ), the maximum wind resistance rating may be between 150 and 195 psf, depending on the type of roof cover and insulation or topping board it is adhered to.where higher wind ratings are needed for steel deck roofs in perimeter and corner areas, higher wind uplift resistance can be achieved by using mechanically attached base plies or mechanically attached single-ply membranes, as they are dependent on the resistance of the interaction of the fastener stress plate and the membrane, or the pullout of the screw from the deck, and not the insulation board.

37 Roof Deck Securement and Above-Deck Roof Components 1-29 FM Global Property Loss Prevention Data Sheets Page 37 Rows of fasteners for mechanically fastened roof covers should run perpendicular to the deck ribs. When rows of fasteners for roof covers run parallel to the deck ribs, the load is not uniformly distributed to the deck or its points of securement. In such cases, the wind uplift load is generally shared by the equivalent of only two or three deck fasteners or welds, which may cause failure of the deck at its point of securement. Recommendations in this document are intended to provide a safety factor of 2.0 between the rated or ultimate wind resistance of above deck components and deck securement and design wind pressure. This safety factor is intended to compensate for defects in workmanship and materials, loads in excess of the design load, and adverse effects due to aging. Wind uplift pressure may be influenced by the type of roof deck. If the deck is of panel construction, which contain joints, such as steel, wood, or pre-cast gypsum or concrete plank decks, the internal building pressure is allowed to act on the underside of the above-deck components. Decks such as gypsum or concrete are cast-in-place from a cementitious slurry that hardens into a monolithic material. These decks have virtually no spaces to allow internal pressure to act on the underside of the roof cover and insulation. As a result the net load on the above-deck components is less with monolithic decks than for panel-type decks. Precast gypsum and concrete plank decks do have joints which allow internal pressure to act on the roof underside. All necessary adjustments for monolithic decks have been considered during Approval testing. Insulation that is pre-secured below a mechanically fastened roof cover is subject to internal pressure, which is constant throughtout the internal plan area. Increases in total uplift pressure at perimeter and corner areas are due to large increases in external pressures there Wind Damage Wind can damage roofs in a number of ways. Types of damage include: (a) perimeter flashing components removed or loosened; (b) roof covering and/or insulation removed; (c) roof covering and/or insulation lifted and dropped back into place; (d) structural roof deck panels dislodged or lifted; (e) roof covering damaged by impact from wind blown objects; (f) dislodged roof protrusions such as vents, skylights and pipes; and (g) roof deck delamination within itself, such as can occur with improperly installed or designed lightweight insulating concrete. Any or all of the various kinds of damage can occur in one windstorm. Uplift damage to the roof deck usually results in significant additional damage to above-deck components. This damage can spread a considerable distance beyond the damaged deck even if the above-deck components are properly secured. After a small area of deck becomes dislodged, the wind can act on the loose edges of the roof cover and insulation. The wind can then peel the cover from the deck Inferior Construction When the uplift resistance of the roof is less than that needed for the applicable wind loading, the roof is vulnerable to wind damage and is termed inferior. This can occur for several reasons, one being deficiencies in the installation of the roof deck. When materials that are not FM Approved are used, the construction also may be inferior. In some cases, inferior construction can be determined from the specifications. The inferior designation is an indication of poor wind resistance, not fire classification Steel Deck The roof deck provides the structural support for the roof assembly. It should have sufficient strength and stiffness to prevent the above-deck layers from flexing excessively and separating due to live loads (snow, construction, wind) or dead loads. Some decks, such as structural concrete, are inherently stiff. For others, such as steel, particular attention must be paid to the design to ensure limited deflection and stress within the deck. This is achieved by: (1) limiting the deck span, (2) fastening the panels adequately to the supporting members, and (3) fastening the panel side laps. Other methods of limiting deflection and stress within the deck to acceptable limits, particularly at higher wind pressures, include using higher strength steel, using thicker or stiffer deck (depth, rib configuration), or using spans that are further reduced. Excessive deflections can cause fracturing of the above-deck insulation and delamination of the roof cover, and excessive stress within the deck can cause the deck to buckle. The combination of a relatively high needed wind rating and relatively long deck spans can result in buckling of steel deck.

38 Page 38 FM Global Property Loss Prevention Data Sheets When plug welding is used to secure steel deck to supporting members, care is needed to prevent the hole from becoming too large. For decks thinner than 22 ga. ( in., mm), this can be prevented by using weld washers. A typical weld washer is a 16 ga. (0.06 in., 1.52 mm) piece of steel about 1 in. (25 mm) square, having a hole in the center. The washer is placed on the deck and secured by burning a hole through the deck and welding the washer to the supporting member. Most experts do not recommend weld washers on decks that are 22 ga. ( in., mm) or thicker. Research at FM Global has shown no detrimental effects on tensile (pull-over) weld strength for 22 ga. ( in., mm) deck when weld washers are used. Deck side laps also need to be secured. If a worker stands on the bottom panel while fastening the lap, the worker s weight can deflect that panel downward so that adequate fastening may not be possible. If the mating parts are then fastened, the deflected panel will remain in that position. The result is an uneven deck surface, voids under parts of the insulation, and a lack of load distribution (Figs. 9a and b). Welding of side laps of decks thinner than 18 ga. ( in., mm) is not recommended due to the difficulty of obtaining consistent weld quality Examples of Design Considerations For Proposed Steel Deck Example No. 1. A proposed building in a non-hurricane prone region is to use a low slope, steel deck roof and is to be designed as an enclosed building. The basic wind design pressure for the field of the roof is 45 psf (unfactored). The respective pressure coefficients for the perimeter and corner areas are 1.68 and 2.53, respectively, so the design pressures for those areas are 76 psf and 114 psf. The building designer would like to use the same deck type and same center-to-center joist spacing throughout the entire building. Deck lengths will meet a three span condition. If a in. deep, 22 gauge, wide rib deck with a yield stress of 33,000 psi (grade 33) is proposed, what is the maximum span that can be used? Solution The highest pressure needed is 114 psf. Since Table 11 incorporates a safety factor, it is not necessary to multiply the design pressures by a safety factor such as is done for above deck components. Per Table 11, for a triple span condition with in. deep, 22 gauge, wide rib deck, a span of 6 ft yields an allowable pressure of 114 psf. That is adequate. This is also the maximum FM Approved span for this specific deck. Example No. 2. The same circumstances as in Example No. 1 above, except the building owner wishes to design for a 23% higher wind speed. That results in design pressure that are 1.5 times that of Example No. 1, since the pressure is proportional to the square of the velocity. This yields design pressures of 67.5, 114, and 171 psf, respectively, for the field, perimeter, and corner areas. In this case, a in. deep, 22 gauge, wide rib deck with a span of 6 ft is adequate for the field and perimeter area, but not the corners. In order to still use this very common deck type, several options are available. In order of preference they are: a) A Grade 80 (F y = 80,000 psi) steel deck could be used. To determine the allowable wind pressure for the grade 80 deck, multiply the allowable pressure for that of the grade 33 deck by 1.55 (see footnotes to Table 11). That yields an allowable pressure of 177 psf (114 psf times 1.55), which is adequate. b) Intermediate steel joist could be installed to support grade 33 deck in the corner areas to reduce the span to 3 ft (0.9 m), or c) Overlay a second layer of grade 33 deck in the corners. Screw the two decks together using side-lap fasteners at each side lap and every other deck rib. The spacing between fasteners within rows should be in accordance with Option a) is preferred since the FM Approval for above-deck components rated for such pressures will likely require a Grade 80 deck, and it is likely the most cost effective solution as well. Example No. 3. Recommend deck securement for the design pressures noted in Example No. 2, given that an FM Approved roof system (safety factor of 2.0 times 67.5 psf) is proposed and the specific Approval listing requires in. deep, 22 gauge, wide rib, Grade 80 deck with FM Approved deck fasteners every 6 in. (150 mm, every rib) on center.

39 Page 39 FM Global Operating Standards Solution: Per the Approval listing, FM Approved deck fasteners should be provided every 6 in. (150 mm, every rib) on center in the field of the roof. Two fasteners per deck rib should be provided in the perimeter and corner areas. Side lap fastening should be 30 in. (0.76 m) on center in the field of the roof, and 15 in. (0.38 m) on center in the perimeter and corners. 4.0 REFERENCES 4.1 FM Global Data Sheet 1-5, Removal and Shipping of Roof Deck Samples for Calorimeter Testing Data Sheet 1-12, Ceilings and Concealed Spaces Data Sheet 1-13, Chimneys Data Sheet 1-22, Maximum Foreseeable Loss Data Sheet 1-28, Wind Design Data Sheet 1-30, Repair of Wind Damaged Roof Systems Data Sheet 1-31, Metal Roof Systems Data Sheet 1-32, Existing PVC Roof Covers Data Sheet 1-33, Safeguarding Torch-Applied Roof Installations Data Sheet 1-49, Perimeter Flashing Data Sheet 1-52, Field Uplift Tests Data Sheet 1-54, Roof Loads for New Construction Approval Guide, a publication of FM Approvals FM Approvals RoofNav 4.2 Others American Society of Civil Engineers ASCE Standard 7-05, Minimum Design Loads for Buildings and Other Structures ASTM D448 UL Fire Resistance Directory, Volume 1, published annually APPENDIX A GLOSSARY OF TERMS Effective wind area: The span length times the effective width. For roof cover, roof deck, or wall panel fastening, the effective wind area should not exceed that supported by the fastener or clip (generally reflected in the tables in DS 1-28). FM Approved: References to FM Approved in this data sheet mean the product and services have satisfied the criteria for FM Approval. Refer to the Approval Guide, a publication of FM Approvals, and RoofNav for a complete listing of products and services that are FM Approved. Hurricane pone regions: Areas vulnerable to hurricanes. Areas in the United States and its territories include: 1. The U.S. Atlantic Coast and Gulf of Mexico Coast, including parts of Mexico and Central America, where the basic wind speed per DS 1-28 is greater than 90 mph (40 m/s), and 2. Hawaii, Puerto Rico, Guam, Virgin Island, and American Samoa. For locations outside the United States, consider any areas that are in a tropical cyclone region or typhoon prone region. These include, but are not limited to, parts of Australia, the Bahamas, Bermuda, India, Indonesia, Bangladesh, the Philippines, Japan, South Korea, Hong Kong, Macau, Vietnam, and Taiwan, where the basic wind speed per DS 1-28 is greater than 90 mph (40 m/s). Square: A roofing term meaning 100 ft 2 (9.28 m 2 ) of roofing area. Tropical cyclone prone region: An area prone to tropical storms, in which winds rotate about a center of low atmospheric pressure (clockwise in the southern hemisphere and counter-clockwise in the northern hemisphere), where the basic wind speed per DS 1-28 is greater than 90 mph (40 m/s).

40 Page 40 FM Global Property Loss Prevention Data Sheets Typhoon-prone region: Areas including, but not limited to, the Philippines, China, Taiwan, Japan, South Korea, Hong Kong, Macau, and Vietnam. APPENDIX B DOCUMENT REVISION HISTORY September Minor editorial changes were made for this revision. September Hailstorm hazard map was reformatted. No technical changes were made. June Clarification was made to recommendation January The following changes were made for this revision: Clarification was added to Section Footnote of Table 1 was revised to clarify its intent. Minor revision to Figure 6 was made. August Changes were made as follows: Recommendation was revised to clarify its intent. Recommendation was revised to allow prescriptive enhancements for non-hurricane-prone regions where Class 1-90 systems are needed. In addition, other acceptable enhancements were added where Class 1-90 systems are needed in hurricane-prone regions. Recommendation was simplified and related portions of section 3 expanded. Table 1A was deleted. Footnote 2 of Table 1 was relocated to make it clearer that it applied to the entire table. February Changes were made as follows: Guidance was added and modified for steel deck span and securement to implement optional designs for wind speeds higher than the basic wind speed shown in DS Allowable wind pressure vs. deck span tables were added for common steel deck types, along with multipliers to determine wind pressures for higher grades of steel. Example problems for deck design were added. Recommendations were added to help improve the installation quality of lightweight insulating concrete (LWIC). Recommendation was relocated from DS 1-29R. Recommendation , related to prescriptive enhancements for mechanically fastened insulation with adhered roof covers, was modified to prevent misinterpretation of intent. May Editorial changes were made to the Table 1. January Recommendations , , , , , , and were revised, and , , and were added. These recommendations focus on using mechanically attached roof covers with steel deck roofs in high wind areas, and orientation of roof cover fasteners to properly distribute the wind load to steel deck securement points. In addition, Table 1 was modified to provide a full safety factor of 2.0 in the perimeter and corner areas in all cases. May Minor editorial changes were made. January Editorial changes were made. September Minor editorial changes were made for this revision. January Deck securement for wind uplift has been relocated here, and was formerly found in Data Sheet September This revision of the document has been reorganized to provide a consistent format.