FEMA P-499: Home Builder's Guide to Coastal Construction

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7 ROOFING Wind-driven rain penetration: Currently there is no adequate standard test method to evaluate the potential for wind-driven rain to enter attics through soffit vent openings, such as those shown in Figure 6. To avoid water entry at soffit vents, options include eliminating soffit vents and providing an alternate method for air to enter the attic, or design for an unvented attic. Another approach is to place filter fabric (like that used for heating, ventilation, or cooling [HVAC] system filters) above the vent openings; however, such an approach needs to be custom designed. Figure 6. Fiber cement soffit with ventilation slots (red arrow). Fascia cover: Field investigations after Hurricane Ike showed many cases where the aluminum fascia cover (fascia cap) from the fascia board was blown off (Figure 7). The fascia cover normally covers the ends of vinyl and aluminum soffits. When the fascia cover is blown off, the ends of the soffit panels are exposed to wind and wind-driven rain. Rain screen wall venting: In lieu of providing soffit vents, another method to provide attic air intake is through a pressure-equalized rain screen wall system as discussed in Siding Installation in High-Wind Regions, Hurricane Ike Recovery Advisory. This alternative approach eliminates soffit vents and their susceptibility to wind-driven rain entry. 4 of 8 12/10 Figure 7. Loss of fascia cover exposes ends of vinyl soffit to direct entry of wind-driven rain. The IRC currently has no guidelines for the installation of fascia covers. Aluminum fascia covers are typically tucked under the roof drip edge and facenailed every few feet. More frequent nailing would help secure the fascia cover, but would also inhibit normal thermal movement, which can cause unattractive warping and dimpling of the cover. Vinyl fascia covers are available, which are attached to a continuous strip of utility trim placed underneath the drip edge. This provides a somewhat more secure, continuous attachment and allows for thermal movement. Aluminum fascia covers can also be field notched and installed with utility trim. Ridge Vents Key Issues n Ridge vents are frequently fastened down using ordinary roofing nails since these are normally handy. It is fairly common to find ridge vents dislodged or blown off during a hurricane (Figure 8). Even a partially dislodged ridge vent can begin to act like a scoop that collects winddriven rain and directs it into the attic. n Most roofing manufacturers now make ridge vents that have passed wind-driven water tests. They are identified as having passed Florida Building Code’s Product Approvals or Testing Application Standard (TAS) 100(A). Typically, they include a baffle in front of the vent tubes that provide the passageway for hot attic gasses to escape. This baffle is intended to trip any flow of wind and water blowing up the surface of the roof and deflect it over the top of the roof ridge. 7.5: MINIMIZING WATER INTRUSION THROUGH ROOF VENTS IN HIGH-WIND REGIONS HOME BUILDER’S GUIDE TO COASTAL CONSTRUCTION
Figure 8. This metal ridge vent was attached with widely spaced roofing nails. Checking Ridge Vents and Their Installation When they are used, ridge vents are the last part of the roof to be installed. Consequently, the connection is readily accessible and frequently visible without having to pry up the edge of the vent cover top. Check the type and condition of the fasteners. If the fasteners are nails, replacement of the fasteners is in order. If the vent has clear holes or slots without any baffle or trip next to the edge of the vent channels, the vent is probably not one that is resistant to water intrusion and you should consider replacing the ridge vent with one that has passed the wind-driven water intrusion tests. Remedial Measures Replace nails with gasketed stainless steel wood screws that are slightly larger than the existing nails and, if possible, try to add fasteners at locations where they will be embedded in the roof structure below and not just into the roof sheathing. Close spacing of fasteners is recommended (e.g., in the range of 3 to 6 inches on center, commensurate with the design wind loads). If the ridge vents are damaged or are one of the older types that are not resistant to water intrusion, they should be replaced with vents that have passed the wind-driven water intrusion tests. 7.5: MINIMIZING WATER INTRUSION THROUGH ROOF VENTS IN HIGH-WIND REGIONS HOME BUILDER’S GUIDE TO COASTAL CONSTRUCTION Slotting the Deck When ridge venting is being added to a roof that previously did not have it, it is necessary to cut a slot through the decking. When doing so, it is important to set the depth of the saw blade so that it only slightly projects below the bottom of the decking. At the residence shown in Figure 8, the saw blade cut approximately 1 1/2 inches into the trusses and cut a portion of the truss plate (red arrow). Figure 9. Gable end vent. Gable End Vents Key Issues n Virtually all known gable end vents (Figure 9) will leak when the wall they are mounted on faces into the wind-driven rain. The pressures developed between the outside surface of the wall and the inside of the attic are sufficient to drive water uphill for a number of inches and, if there is much wind flow through the vent, water carried by the wind will be blown considerable distances into the attic. 5 of 8 12/10 ROOFING 7
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Home Builder’s Guide to Coastal C
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G GUIDE 2 of 6 12/10 Fact Sheet No.
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G GUIDE 4 of 6 12/10 Fact Sheet No.
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G GUIDE 6 of 6 12/10 Category Categ
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1 GENERAL What Should Owners and Ho
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Summary of Coastal Construction Req
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Foundation Orientation of Lowest Ho
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Certification Elevation NFIP 60.3(b
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Coastal Construction Requirements a
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Coastal Construction Requirements a
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Using a Digital Flood Insurance Rat
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Sample DFIRM This map is a portion
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Lowest Floor Elevation HOME BUILDER
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V Zone Design and Construction Cert
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Designing for Flood Levels Above th
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FIRMs depict the limits of flooding
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Figure 6. Mold and biological/chemi
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Other Considerations As previously
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Coastal Building Materials HOME BUI
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Location of Material Use Name of Ma
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n Metal-plate-connected trusses sho
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Non-Traditional Building Materials
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Things to consider if building with
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Figure 5. An example of a wall cavi
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Moisture Barrier Systems HOME BUILD
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How Do Siting and Design Decisions
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Selecting a Lot and Siting the Buil
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Foundations in Coastal Areas HOME B
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prohibited in V Zones but are recom
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3 FOUNDATIONS Table 1. Example foun
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3 FOUNDATIONS Additional Resources
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3 FOUNDATIONS 2 of 6 12/10 Figure 2
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3 FOUNDATIONS 4 of 6 12/10 Figure 4
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3 FOUNDATIONS Additional Resources
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3 FOUNDATIONS Piers vs. Piles Pier
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HOME BUILDER’S GUIDE TO COASTAL C
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If a stemwall and floor slab system
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4 LOAD PATHS If a connection fails,
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4 LOAD PATHS Gable end wall - cut c
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Use of Connectors and Brackets HOME
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Important These are examples of typ
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Page 94 and 95: 5 WALL SYSTEMS 2 of 3 12/10 Figure
Page 97 and 98: Siding Installation in High-Wind Re
Page 99 and 100: n Use aluminum, galvanized steel, o
Page 101 and 102: Figure 8b. Wood siding installation
Page 103 and 104: Energy Conservation and Air Barrier
Page 105 and 106: Attachment of Brick Veneer in High-
Page 107 and 108: Construction Guidance The brick ven
Page 109: Table 1. Brick Veneer Tie Spacing N
Page 112 and 113: 6 OPENINGS Although not discussed i
Page 115 and 116: Protection of Openings- Shutters an
Page 117 and 118: What Types of Shutters Are Availabl
Page 119 and 120: Are There Special Requirements for
Page 121 and 122: Roof Sheathing Installation HOME BU
Page 123: Common Sheathing Attachment Mistake
Page 126 and 127: 7 ROOFING 5. Apply a single layer o
Page 129 and 130: Asphalt Shingle Roofing for High Wi
Page 131: After the shingles have been expose
Page 134 and 135: 7 ROOFING Design and Construction G
Page 137 and 138: Minimizing Water Intrusion Through
Page 139: Checking Soffit Material Installati
Page 143 and 144: Gable Rake Vents Key Issues n Gable
Page 145 and 146: Metal Roof Systems in High-Wind Reg
Page 147 and 148: Construction Guidance n Consult loc
Page 149: Additional Resources For general in
Page 152 and 153: 8 ATTACHMENTS Space Below the BFE
Page 154 and 155: 8 ATTACHMENTS n Siding used on the
Page 157 and 158: Decks, Pools, and Accessory Structu
Page 159 and 160: uildings. Pools can be designed to
Page 161 and 162: Purpose: To identify the special co
Page 163: Fuel n Fuel tanks should be install
Page 166 and 167: 9 REPAIRS n Pre-FIRM or post-FIRM b
Page 168 and 169: 9 REPAIRS n If a lateral addition c
Page 170 and 171: 9 REPAIRS Enclosures of Areas Below
Page 173 and 174: Repairs, Remodeling, Additions, and
Page 175 and 176: Vertical additions may also impose
Page 177 and 178: n Soffits should be inspected follo
Page 179 and 180: References and Resources HOME BUILD
Page 181 and 182: FEMA. NFIP Technical Bulletin 5-08,
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FEMA P-499: Home Builder's Guide to Coastal Construction

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