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

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3 FOUNDATIONS Table 1. Example foundation adequacy calculations for a two-story house supported on square timber piles and situated away from the shoreline, storm surge, and broken waves passing under the building, 130-mph basic wind speed per ASCE 7-05 (167-mph equivalent ASCE 7-10 basic wind speed for Risk Category II buildings), soil = medium dense sand. Shaded cells indicate the foundation fails to meet bending (P) and/or embedment (E) requirements. 2 of 4 12/10 Pile Embedment Before Erosion and Scour 10 feet 15 feet 20 feet Erosion and Scour Conditions Pile Diameter, Ø 8 inch 10 inch 12 inch Erosion = 0, Scour = 0 P, E E OK Erosion = 0, Scour = 2.0Ø P, E E E Erosion = 1, Scour = 2.5Ø P, E E E Erosion = 1, Scour = 3.0Ø P, E E E Erosion = 1, Scour = 4.0Ø P, E P, E E Erosion = 0, Scour = 0 P OK OK Erosion = 0, Scour = 2.0Ø P OK OK Erosion = 1, Scour = 2.5Ø P OK OK Erosion = 1, Scour = 3.0Ø P OK OK Erosion = 1, Scour = 4.0Ø P, E P, E E Erosion = 0, Scour = 0 P OK OK Erosion = 0, Scour = 2.0Ø P OK OK Erosion = 1, Scour = 2.5Ø P OK OK Erosion = 1, Scour = 3.0Ø P OK OK Erosion = 1, Scour = 4.0Ø P P OK Pile Layout The foundation engineer and designer determine the pile layout together. Accurate placement and correction of misaligned piles is important. The use of a drive template for guiding the pile driving operation greatly increases the accuracy of the pile location and need for difficult remediation. A drive template is a temporary guide structure that is installed in a manner to restrict the lateral movement of the piles during driving. The pile template is reused for each row of piles to assure consistent spacing and alignment. Pile placement should not result in more than 50 percent of the pile cross section being cut for girder or other connections. Verify proper pile locations on drawings before construction and clarify any discrepancies. Layout can be done by a licensed design professional or surveyor, a construction surveyor, the foundation contractor, or the builder. The layout process must always include establishing an elevation for the finished first floor. Construction of the first-floor platform should not begin until this elevation is established (see Fact Sheet No. 1.4, Lowest Floor Elevation). Installation Methods Piles can be driven, augered, or jetted into place. The installation method will vary with soil conditions, bearing requirements, equipment available, and local practice. One common method is to initially jet the pile to a few feet short of required penetration, then complete the installation by driving with a drop hammer. Driving the pile even a few feet helps assure the pile is achieving some end-bearing capacity and some skin friction. Full depth driving where achievable provides for a pile foundation that has several advantages that merit consideration. Pile Bracing The engineer determines pile bracing layout. Common bracing methods include knee and diagonal bracing. Knee bracing is an effective method of improving the performance of a pile system without creating an obstruction to the flow of water and debris from a design event. Because slender bracing is susceptible to buckling, slender bracing should be considered as tension only. Bracing can become an obstruction, however, and increase a foundations exposure to wave and debris impact. Bracing is often oriented perpendicular to the shoreline so that it is not struck broadside by waves, debris, and velocity flow (see Figure 2). Temporary bracing or jacking to align piles and hold true during construction is the responsibility of the contractor. It is recommended that pile bracing be used only for reducing the structure’s sway and vibration for comfort. In other words, bracing should be used to address serviceability issues and not strength issues. The foundation design should consider the piles as being un-braced as the condition that may occur when floating debris removes or damages the bracing. If the pile foundation is not able to provide 3.2: PILE DESIGN AND INSTALLATION HOME BUILDER’S GUIDE TO COASTAL CONSTRUCTION
Figure 2. Diagonal bracing schematic. the desired strength performance without bracing then the designer should consider increasing the pile size. Pile bracing should only be for comfort of the occupants, but not for stability of the home. Field Cutting and Drilling A chain saw is the common tool for making cuts and notches in wood piles. After making cuts, exposed areas should be field-treated with the proper wood preservative to prevent decay. This involves applying the preservative with a brush to the cut or drilled holes in the pile until no more fluid is drawn into the wood. Connections The connection of the pile to the structural members is one of the most critical connections in the structure. Always follow design specifications and use corrosion-resistant hardware. Strict attention to 3.2: PILE DESIGN AND INSTALLATION HOME BUILDER’S GUIDE TO COASTAL CONSTRUCTION detail and good construction practices are critical for successful performance of the foundation (see Fact Sheet Nos. 1.7, Coastal Building Materials, and 3.3, Wood-Pile-to-Beam Connections). Verification of Pile Capacity Generally, pile capacity for residential construction is not verified in the field. If a specified minimum pile penetration is provided, bearing is assumed to be acceptable for the local soil conditions. Subsurface soil conditions can vary from the typical assumed conditions, so verification of pile capacity is prudent, particularly for expensive coastal homes. Various methods are available for predicting pile capacity. Consult a local foundation engineer for the most appropriate method for the site. 3 of 4 12/10 FOUNDATIONS 3
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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
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 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 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
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
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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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