RECOMMENDED RESIDENTIAL CONSTRUCTION FOR COASTAL AREAS
Building on Strong and Safe Foundations
FEMA P-550, Second Edition / December 2009


Appendix C. Assumptions Used in Design 
Coastal Areas Foundation Designs
The foundation designs proposed in Appendix A are based on the following 
standards and codes:

ASCE 7-05
Minimum Design Loads for Buildings and Other Structures American Society of 
Civil Engineers (ASCE) 

ASCE 24 
Flood Resistant Design and Construction American Society of Civil Engineers 
(ASCE)

ACI 318-02
Building Code Requirements for Structural Concrete American Concrete Institute 
(ACI)

ACI 530-02/ASCE 5-02/TMS 402-02
Building Code Requirements for Masonry Structures American Concrete Institute 
(ACI) American Society of Civil Engineers (ASCE) The Masonry Society (TMS) 

ANSI/AF&PA NDS-2005 
National Design Specifications for Wood Construction American Forest & Paper 
Association (AF&PA) American National Standards Institute American National 
Standards Institute (ANSI)American Wood Council (AWC) 

IRC-2003 
2003 International Residential Code for One- and Two-Family Dwellings 
International Code Council (ICC)

FEMA 550 has been checked and found to be consistent with both the 2006 and the 
2009 IRC.

To provide flexibility for the builder, a range of dead loads and building 
dimensions was used for calculating reactions on the foundation elements. For 
uplift and overturning analyses, the structure was assumed to be relatively 
light and narrow, and constructed with a relatively low-sloped roof. For sliding 
analyses, the home was considered relatively deep and constructed with a steeper 
roof slope. For the gravity loading analysis, a heavier structure was assumed. 

Dead Loads 

For Use in ASCE 7-05 ASD Uplift/Overturning Load Combination #7 (0.6D + W +H)

First Floor 8 psf Vinyl flooring, 5/8-inch plywood sub-floor and 2 by 8 joists 
16 inches on centers

Second Floor 10 psf First floor components plus 1 layer of ½-inch gypsum drywall

Wall 9 psf Wood siding, 2 by 4 studs 16 inches on centers, ½-inch plywood wall 
sheathing, and one layer of ½-inch gypsum drywall

Roof12 psf200 lb/sq asphalt roofing, 15 lb/sq felt, ½-inch plywood decking, 2 by 
4 top and bottom truss chords 24 inches on centers, ½-inch gypsum drywall 
ceiling finish

Dead Loads 

For Use in ASCE 7-05 ASD Gravity Load Combination #2 (D + H + F + L + T)
First Floor 16 psf Dead loads increased 8 lb/sf to account for additional 
finishes like hardwood flooring (4 lb/sf), ½-inch slate (7 lb/sf), or thin set 
tile (5 lb/sf)

Second Floor 18 psf

Wall 10 psf Wall weight increased to account for cement composite siding

Roof 12 psf

Concrete 150 psf Normal weight concrete. Footings for continuous perimeter walls 
were also sized to support full height brick veneer at 40 psf. 

Masonry 115 psf Medium weight block

Grout 105 psf

Brick Veneer 40 psf

Wind Loads 

Designs provided for 120-mph, 130-mph, 140-mph, and 150-mph zones (3-second gust 
wind speeds per ASCE 7-05). Wind analysis used Method 2 for buildings of all 
heights.  

Exposure 

Category C Open terrain with scattered obstructions generally less than 30 feet 
in height; shorelines in hurricane-prone areas

K sub zt = 1 No topographic effects (i.e., no wind speedup effects from hills, 
ridges, or escarpments) 

K sub d = 0.85 Wind directionality factor (for use with ASCE 7-02 load 
combinations)

K sub z, K sub h Velocity pressure coefficients for Exposure Category C  
Flood Loads 

V zone  Breaking wave load from a wave with height 78 percent of still- water 
depth (d sub s) Flood velocity (fps) equal to (gd sub s)1/2 up to a maximum of 
10 fps (FEMA 55 Upper Bound)

Coastal A zone  Breaking wave load from 1½ foot up to a 3-foot high wave Flood 
velocity (fps) equal to (gds)1/2 up to a maximum of 5 fps (FEMA 55 Upper Bound)

Non-Coastal A zone Breaking wave load up to a 1½-foot high wave Flood velocity 
(fps) equal to stillwater flood depth (d sub s) (in feet)(FEMA 55 Lower Bound)
Lateral Loads (on stem walls
Lateral earth pressures from saturated soils 100 pounds per cubic foot (pcf) 
Surcharge for slab weight and first floor live load65 pounds per square foot 
(psf) 

Live Loads

First Floor 40 psf

Second Floor 30 psf

Roof 20 psf

Soil Bearing Capacity

1,500 psf presumptive value for clay, sandy clay, silty clay, clayey silt, and 
sandy silt (CL, ML, MH, and CH soils) (2009 IRC)

Building Dimensions

Building Width 14 ft (per module)

Building Depth max 42 ft min 24 ft

Shear Wall Spacing max 42 ft

Floor Height 10 ft (floor to floor dimension)

Roof Pitch Ratio min 3:12 Uplift and overturning calculation max 12:12 	Sliding 
calculation

Roof Overhang 2 ft