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

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1 GENERAL Why Are FIRMs and DFIRMs Important? n FIRMs and DFIRMs show the boundaries of modeled flood hazard areas in a community. n SFHAs shown on the maps are used to set flood insurance rates and premiums. n The 1-percent-annual-chance flood elevations and flood depths shown on FIRMs and DFIRMs are the minimum regulatory elevations on which community floodplain management ordinances and building codes are based. n The information shown on these maps can affect the design and construction of new buildings and infrastructure, the improvement and repair of existing buildings, and additions to existing buildings (see Fact Sheet Nos. 1.2, Summary of Coastal Construction Requirements and Recommendations for Flood Effects, and 8.3, Protecting Utilities). What Are Flood Zones and Base Flood Elevations, and How Do They Affect Coastal Buildings? n BFEs are typically shown on DFIRMs for riverine flood zones (Zone A, AE, AO, and AH) and coastal flood zones (Zone V and VE). The BFE is the predicted elevation of flood waters and wave effects during the 1-percent-annual-chance flood (also known as the base flood). The BFE is referenced to the vertical datum shown on the DFIRM. Most have been updated to the 1988 North American Vertical Datum. n The minimum lowest floor elevation and the foundation type and design for new construction* are determined by the BFE and flood zone, as required in the community’s floodplain management ordinance and building code (see Fact Sheet Nos. 1.4, Lowest Floor Elevation, and 3.1, Foundations in Coastal Areas). This ordinance, along with the most current DFIRM and FIS, are adopted by resolution to meet NFIP participation requirements. Use of these tools supports community planning, zoning, and building inspection programs that require specific structure design and new construction* in high-hazard coastal floodplains. Some communities have adopted higher standards for coastal construction (e.g., lowest floor elevations above the BFE [freeboard], restrictions on foundation types, and enclosures in Zone A). Builders should consult their local jurisdiction for details. * Note that new construction may include some additions, improvements, repairs, and reconstruction. Consult the community about substantial improvement and substantial damage requirements. 2 of 4 12/10 Flood Hazard Zones in Coastal Areas (See the sample DFIRM that follows) Zone V: Areas closest to the shoreline including the Primary Frontal Dune (PFD), subject to storm wave action, high-velocity flow, and erosion during 100-year storm events. Elevations are not provided. Zone VE: Base Flood Elevations (BFEs) are provided on the DFIRM and an additional hazard can be present associated with storm waves greater than 3 feet and including the PFD. BFEs are derived from detailed analyses shown in the FIS. Zone A: Areas subject to flooding during the 1-percent-annual-chance flood. Flood conditions are less severe than in Zone V and MOWAs due to lower wave forces. Because detailed analysis has not been performed, BFEs and flood depths are not provided. Zone AE: Depicts BFEs on the DFIRM. Further details are provided in the FIS on areas where hydrology and hydraulic modeling was performed to determine flood hazard risk. Area of Moderate Wave Action (MOWA): Area landward of Zone V, or landward of an open coast without a mapped Zone V. During base flood conditions, the potential wave height in this area is between 1.5 and 3 feet above the 1-percent-annual-chance stillwater flood depth. While this area is not specifically labeled on the DFIRM panel, this is the area between the LiMWA and the VE/AE zone boundary. In many codes and standards it is referred to as the “Coastal A Zone.” Zone AO: Areas subject to shallow flooding or sheet flow during the 1-percent-annual-chance flood. If they appear on a coastal DFIRM they will most likely be found on the landward slopes of shoreline dunes and overtopped structures. Flood depths, rather than BFEs, are shown for Zone AO. Zone AH: Areas subject to inundation by 1-percentannual-chance shallow flooding (usually areas of ponding) where average depths are between 1 foot and 3 feet. Zone X: Areas with a lower probability of flooding (
Sample DFIRM This map is a portion of the DFIRM for the Town of Oyster Bay and the City of Glen Cove in Nassau County, New York. Several important things to note are highlighted: The community identification number is 360465 for Glen Cove and 360483 for Oyster Bay. The panel number is 19. Note that an Index Map is available showing all DFIRM panels for all communities within Nassau County. The effective date of the DFIRM is September 11, 2009. The map scale is shown along with shorelines, roads, flood zones, and BFEs. (The scale and north arrow are usually shown in the “Key to the Map” along the left edge of the DFIRM.) The Limit of Moderate Wave Action—or LiMWA—is shown with a dashed black and white line. This is the area subject to damaging waves between 1.5 – 3 feet above the stillwater BFE. BFEs across the DFIRM section shown range from 11 to 19 feet. The datum (not shown in this sample) is the 1988 North American Vertical Datum. Area designated as a Coastal Barrier Resource System. Zone X has a less than 1-percent chance of flooding; therefore, floodplain ordinance and most flood-related building code requirements are not in effect for this area. However, use of the building standards described in these fact sheets is recommended due to the area’s proximity to coastal waters and wind. 1.3: USING A DIGITAL FLOOD INSURANCE RATE MAP (DFIRM) HOME BUILDER’S GUIDE TO COASTAL CONSTRUCTION 3 of 4 12/10 GENERAL 1
Page 1: Home Builder’s Guide to Coastal C
Page 4 and 5: G GUIDE 2 of 6 12/10 Fact Sheet No.
Page 6 and 7: G GUIDE 4 of 6 12/10 Fact Sheet No.
Page 8 and 9: G GUIDE 6 of 6 12/10 Category Categ
Page 10 and 11: 1 GENERAL What Should Owners and Ho
Page 13 and 14: Summary of Coastal Construction Req
Page 15 and 16: Foundation Orientation of Lowest Ho
Page 17 and 18: Certification Elevation NFIP 60.3(b
Page 19 and 20: Coastal Construction Requirements a
Page 21 and 22: Coastal Construction Requirements a
Page 23: Using a Digital Flood Insurance Rat
Page 27 and 28: Lowest Floor Elevation HOME BUILDER
Page 29 and 30: V Zone Design and Construction Cert
Page 31 and 32: Designing for Flood Levels Above th
Page 33 and 34: FIRMs depict the limits of flooding
Page 35 and 36: Figure 6. Mold and biological/chemi
Page 37 and 38: Other Considerations As previously
Page 39 and 40: Coastal Building Materials HOME BUI
Page 41 and 42: Location of Material Use Name of Ma
Page 43 and 44: n Metal-plate-connected trusses sho
Page 45 and 46: Non-Traditional Building Materials
Page 47 and 48: Things to consider if building with
Page 49 and 50: Figure 5. An example of a wall cavi
Page 51 and 52: Moisture Barrier Systems HOME BUILD
Page 53 and 54: How Do Siting and Design Decisions
Page 55 and 56: Selecting a Lot and Siting the Buil
Page 57 and 58: Foundations in Coastal Areas HOME B
Page 59: prohibited in V Zones but are recom
Page 62 and 63: 3 FOUNDATIONS Table 1. Example foun
Page 64 and 65: 3 FOUNDATIONS Additional Resources
Page 66 and 67: 3 FOUNDATIONS 2 of 6 12/10 Figure 2
Page 68 and 69: 3 FOUNDATIONS 4 of 6 12/10 Figure 4
Page 70 and 71: 3 FOUNDATIONS Additional Resources
Page 72 and 73: 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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Housewrap HOME BUILDER’S GUIDE TO
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n Improper integration with flashin
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5 WALL SYSTEMS 2 of 3 12/10 Figure
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Siding Installation in High-Wind Re
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n Use aluminum, galvanized steel, o
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Figure 8b. Wood siding installation
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Energy Conservation and Air Barrier
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Attachment of Brick Veneer in High-
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Construction Guidance The brick ven
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Table 1. Brick Veneer Tie Spacing N
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6 OPENINGS Although not discussed i
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Protection of Openings- Shutters an
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What Types of Shutters Are Availabl
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Are There Special Requirements for
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Roof Sheathing Installation HOME BU
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Common Sheathing Attachment Mistake
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7 ROOFING 5. Apply a single layer o
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Asphalt Shingle Roofing for High Wi
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After the shingles have been expose
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7 ROOFING Design and Construction G
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Minimizing Water Intrusion Through
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Checking Soffit Material Installati
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Figure 8. This metal ridge vent was
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Gable Rake Vents Key Issues n Gable
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Metal Roof Systems in High-Wind Reg
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Construction Guidance n Consult loc
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Additional Resources For general in
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8 ATTACHMENTS Space Below the BFE
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8 ATTACHMENTS n Siding used on the
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Decks, Pools, and Accessory Structu
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uildings. Pools can be designed to
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Purpose: To identify the special co
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Fuel n Fuel tanks should be install
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9 REPAIRS n Pre-FIRM or post-FIRM b
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9 REPAIRS n If a lateral addition c
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9 REPAIRS Enclosures of Areas Below
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Repairs, Remodeling, Additions, and
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Vertical additions may also impose
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n Soffits should be inspected follo
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References and Resources HOME BUILD
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FEMA. NFIP Technical Bulletin 5-08,
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FEMA P-499: Home Builder's Guide to Coastal Construction

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