All elements of a raised floor system must be properly sized to support the design loads. See Table 8, Typical Building Loads.

Continuous Load Path

A continuous load path must be provided to transfer all lateral and vertical loads from the roof, wall, and floor systems to the foundation. A load path can be thought of as a “chain” running through the building. Because all applied loads must be transferred to the foundation, the load path chain must connect to the foundation. To be effective, each “link” in the chain must be strong enough to transfer loads without breaking. A continuous load path is especially important in areas subject to high winds and/or seismic forces.

figure8

Wind and Seismic Considerations

Construction in areas subject to high-wind and earthquake forces can pose unique problems to the designer and builder. Refer to Figure 8, Wind Loading.

The ANSI/AF&PA Wood Frame Construction Manual for One- and Two-Family Dwellings (WFCM) provides engineered and prescriptive design requirements for wood-frame construction in areas subject to 85-150 mph wind speeds (3-second gusts) and seismic design categories A-D.
Where wind speeds are less than 110 miles per hour, construction should be in accordance with the International Residential Code. In regions where wind speeds equal or exceed 110 miles per hour, raised floor systems should be designed and constructed in accordance with the WFCM.


 

Table 8 Typical Building Loads
Typical Occupancy Live Loads
WEIGHTS IN POUNDS PER SQUARE FOOT (psf)
40 psf Residential — living
30 psf Residential — sleeping
10 psf Residential — attic without storage
Typical Dead Loads
WEIGHTS IN POUNDS PER CUBIC FOOT (pcf)
130 pcf clay brick masonry
144 pcf plain concrete
150 pcf reinforced concrete
WEIGHTS IN POUNDS PER SQUARE FOOT (psf)
Ceilings
0.55 psf gypsum board (per 1/8 inch)
Coverings Roof / Wall
0.40 psf wood structural panel (per 1/8 inch)
2 psf asphalt tile
16 psf cement tile
3 psf wood shingles
Floors & Floor Finishes
16 psf ceramic tile
4 psf wood flooring, 7/8 inch
Framing
11 psf exterior stud walls — 2×4@16″, 5/8″ gypsum board, insulated, 7/16″ wood structural panel
12 psf exterior stud walls — 2×6@16″, 5/8″ gypsum board, insulated, 7/16″ wood structural panel
48 psf exterior stud walls with brick veneer
8 psf interior wood studs with 1/2″ gypsum board each side
10 psf light-frame wood floor assemblies
15 psf light-frame wood roof / ceiling assemblies
8 psf windows, glass, frame and sash
Concrete/Masonry
80 psf 6″-thick concrete walls
55 psf 8″-thick concrete block walls
80 psf clay brick masonry walls

Source: Standard Building Code, 1997 Edition, Table 1604.1 Appendix A.