Locate footings for posts or columns (Figures 32 and 33) so that the members they will support are centered. Footings vary in size depending on the allowable soil pressure and the load they support. On average stable soil, common sizes are 0.4 m2 (4.3 sq. ft.)—about 640 × 640 mm (25 × 25 in.)—for one-storey houses and 0.75 m2 (8 sq. ft.)—870 × 870 mm (34 × 34 in.)—for two-storey houses. The thickness of column footings without reinforcement must be at least 100 mm (4 in.) and must never be less than the column footing’s projection measured from the edge of the column base plate to the edge of the footing. Footings for fireplaces and chimneys are usually placed at the same time as other footings.

Figure 32

Steel column supported on steel bearing plate resting on footings

Figure 33

Wood column supported on concrete footings

Source : Canada Mortgage and Housing Corporation (CMHC)