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

Recommendations

Info

3 FOUNDATIONS Design Considerations for Foundation Walls The design of foundation walls is covered by building codes and standards (e.g., Standard for Residential Construction in High-Wind Regions, ICC 600-2008, by the International Code Council). For flood design purposes, there are six additional design considerations: (1) embedment, (2) height, (3) materials and workmanship, (4) lateral support at the top of the wall, (5) flood openings and ventilation openings, and (6) interior grade elevation. Embedment – The top of the footing should be no higher than the anticipated depth of erosion and scour (this basic requirement is the same as that for piers; see figure at right and Fact Sheet No. 3.4). If the required embedment cannot be achieved without extensive excavation, consider a pile foundation instead. Height – The wall should be high enough to elevate the bottom of the floor system to or above the DFE (see Fact Sheet No. 1.4). Materials and Workmanship – Foundation walls can be constructed from many materials, but masonry, concrete, and wood are the most common. Each material can be specified and used in a manner to resist damage due to moisture and inundation (see Fact Sheet No. 1.7). Workmanship for flood-resistant foundations is crucial. Wood should be preservative-treated for foundation or marine use (aboveground or groundcontact treatment will not be sufficient). Cuts and holes should be field-treated. Masonry should be reinforced and fully grouted (see Fact Sheet No. 4.2 for masonry details). Concrete should be reinforced and composed of a high-strength, low water-to-cement ratio mix. 2 of 3 12/10 Floor slab atop backfilled stemwall foundation Lateral Support at the Top of the Wall – Foundation walls must be designed and constructed to withstand all flood, wind, and seismic forces, as well as any unbalanced soil/hydrostatic loads. The walls will typically require lateral support from the floor system and diaphragm, and connections to the top of the walls must be detailed properly. Cripple walls, where used, should be firmly attached and braced. Flood Openings and Ventilation Openings – Any area below the DFE enclosed by foundation walls must be equipped with openings capable of automatically equalizing the water levels inside and outside the enclosure. Specific flood opening requirements are included in Fact Sheet No. 8.1. Flood openings are not required for backfilled stemwall foundations supporting a slab. Air ventilation openings required by building codes do not generally satisfy the flood opening requirement; the air vents are typically installed near the top of the wall, the flood vents must be installed near the bottom, and opening areas for air flow may be insufficient for flood flow. Interior Grade Elevation – Conventional practice for crawlspace construction calls for excavation of the Floor joist system and crawlspace crawlspace and use of the excavated soil to promote drainage away from the structure (see left-hand figure on page 3). This approach may be acceptable for nonfloodplain areas, but in floodplains, this practice can result in increased lateral loads (e.g., from saturated soil) against the foundation walls and ponding in the crawlspace area. If the interior grade of the crawlspace is below the DFE, NFIP requirements can be met by ensuring that the interior grade is at or above the lowest exterior grade adjacent to the building (see right-hand figure on page 3). When floodwaters recede, the flood openings in the foundation walls allow floodwaters to automatically exit the crawlspace. FEMA may accept a crawlspace elevation up to 2 feet below the lowest adjacent exterior grade; however, the community must adopt specific requirements in order for this type of crawlspace to be constructed in a floodplain. 3.5: FOUNDATION WALLS HOME BUILDER’S GUIDE TO COASTAL CONSTRUCTION
If a stemwall and floor slab system is used, the interior space beneath the slab should be backfilled with compacted gravel (or such materials as required by the building code). As long as the system can act monolithically, it will resist most flood forces. However, if the backfill settles or washes out, the slab will collapse and the wall will lose lateral support. Additional Resources FEMA. NFIP Technical Bulletin 1-08, Openings in Foundation Walls and Walls of Enclosures. 2008. (http://www.fema.gov/plan/prevent/floodplain/ techbul.shtm) 3.5: FOUNDATION WALLS Floor framing Interior grade below adjacent exterior grade Developed in association with the National Association of Home Builders Research Center HOME BUILDER’S GUIDE TO COASTAL CONSTRUCTION FEMA. NFIP Technical Bulletin 11-01, Crawlspace Construction. 2001. (http://www.fema.gov/plan/prevent/floodplain/techbul.shtm) FEMA. Recommended Residential Construction for the Gulf Coast, Building on Strong and Safe Foundations. FEMA 550. 2010. (http://www.fema.gov/library) DFE Floor framing Interior grade at or slightly above adjacent exterior grade Crawlspace construction: Interior grade elevation for Zone A not subject to breaking waves and erosion 3 of 3 12/10 FOUNDATIONS 3
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 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
Page 75: HOME BUILDER’S GUIDE TO COASTAL C
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
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 and 140:
Checking Soffit Material Installati
Page 141 and 142:
Figure 8. This metal ridge vent was
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,
show all

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

Create successful ePaper yourself

Delete template?

Save as template?