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

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1 GENERAL The location of water entry is often difficult to see, and the damage to substrate and structural members behind the exterior wall cladding frequently cannot be detected by visual inspection. Proper Lapping Is the Key… 2 of 2 12/10 Gravity moves water downward. Proper lapping of moisture barrier materials is the key to preventing water intrusion. Most water intrusion problems are related to the improper lapping of materials. Usually, flashing details around doors, windows, and penetrations are to blame. If the flashing details are right and the housewrap or building paper is properly installed, most moisture problems will be prevented. Capillary suction is a strong force and will move water in any direction. Even under conditions of light or no wind pressure, water can be wicked through seams, cracks, and joints upward behind the overlaps of horizontal siding. Proper lap distances and sealant help prevent water intrusion caused by wicking action. How a Redundant Moisture Barrier Works Winter Vapor Drive Interior nish Framing member Must be kept dry Laps should never cause water owing downward to “buck” over seams. Rain Wind Do not count on sealant to substitute for proper lapping. Wind and capillary action can move water in any direction. Wind Proper lap distance is the key to limiting water instrusion caused by wind and capillary action. Always folllow manufacturer’s lap specications or, if a greater lap is specied by the designer, follow designer’s requirements. Siding. The siding is the rst line of defense, but by no means should it be the only protection from outside moisture. Sidings shed most of the water, but some does get through, especially in coastal areas where high winds can drive rain. Housewrap or Building Paper. Housewrap or building paper is a dual-purpose protection layer. It sheds water that gets through the siding and limits air intrusion from the outside. A unique feature of this barrier is that it sheds water, but allows water vapor to pass through. This permits water vapor from the inside to pass through without condensing on the framing. Sheathing. If structural sheathing is used, it should be protected from moisture. Prolonged wetting, especially without the ability to drain the moisture and dry out, will damage the sheathing. Vapor Retarder. In cold regions, a vapor retarder is often used on the warm side of the wall cavity to minimize the movement of vapor from the inside of the building into the wall cavity, where it will condense on the cool framing members. Vapor retarders are typically used only where the predominant vapor drive is from the inside to the outside (cold climates). Developed in association with the National Association of Home Builders Research Center 1.9: MOISTURE BARRIER SYSTEMS HOME BUILDER’S GUIDE TO COASTAL CONSTRUCTION
How Do Siting and Design Decisions Affect the Owner’s Costs? HOME BUILDER’S GUIDE TO COASTAL CONSTRUCTION Technical Fact Sheet No. 2.1 Purpose: To show the effects of planning, siting, and design decisions on coastal home costs. Inland Homes located farther landward may be less appealing to some owners, but will be less prone to damage and will cost less to build, insure, and maintain. Costs, Hazards, and Damage Vary With Location Key Issues n When building a coastal home, initial, operating, and long-term costs (i.e., life cycle costs) must be considered. n Coastal (especially oceanfront) homes cost more to design, construct, maintain, repair, and insure than inland homes. n Determining the risks associated with a particular building site or design is important. n Siting, designing, and constructing to minimum regulatory requirements do not necessarily result in the lowest cost to the owner over a long period of time. Exceeding minimum design requirements costs slightly more initially, but can save the owner money in the long run. Costs A variety of costs should be considered when planning a coastal home, not just the construction cost. Owners should be aware of each of the following, and consider how siting and design decisions will affect these costs: Initial costs include property evaluation and acquisition costs and the costs of permitting, design, and construction. Coastal, Set Back Oceanfront Homes located close to the shore may have spectacular views, but are subject to greater risks, more frequent and more severe damage, and higher construction, maintenance, and insurance costs. Potential $ Losses Operating costs include costs associated with the use of the building, such as the costs of utilities and insurance. 1 Long-term costs include costs for preventive maintenance and for repair and replacement of deteriorated or damaged building components. Risk One of the most important building costs to be considered is that resulting from storm and/or erosion damage. But how can an owner decide what level of risk is associated with a particular building site or design? One way is to consider the probability of a storm or erosion occurring and the potential building damage that results (see matrix). Probability of Occurrence Low Medium High Low Low Risk Low Risk Medium Risk Medium Low Risk Medium Risk High Risk High Medium Risk High Risk Extreme Risk 1 Note: Flood insurance premiums can be reduced up to 60 percent by exceeding minimum siting, design, and construction practices. See the V Zone Risk Factor Rating Form in FEMA’s Flood Insurance Manual (http://www.fema.gov/nfip/manual.shtm). 2.1: HOW DO SITING AND DESIGN DECISIONS AFFECT THE OWNER’S COSTS? HOME BUILDER’S GUIDE TO COASTAL CONSTRUCTION 1 of 2 12/10 PLANNING 2
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 and 24: Using a Digital Flood Insurance Rat
Page 25 and 26: Sample DFIRM This map is a portion
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: Moisture Barrier Systems HOME BUILD
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
Page 75 and 76: HOME BUILDER’S GUIDE TO COASTAL C
Page 77: If a stemwall and floor slab system
Page 80 and 81: 4 LOAD PATHS If a connection fails,
Page 82 and 83: 4 LOAD PATHS Gable end wall - cut c
Page 85 and 86: Use of Connectors and Brackets HOME
Page 87 and 88: Important These are examples of typ
Page 89 and 90: Housewrap HOME BUILDER’S GUIDE TO
Page 91: n Improper integration with flashin
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
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Energy Conservation and Air Barrier
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Attachment of Brick Veneer in High-
Page 107 and 108:
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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