9.15.3.3 — Application of Footing Width and Area Requirements

(1) Except as provided in Sentences (2) and (3) and in Articles 9.15.3.5. to 9.15.3.7., the minimum footing width or area shall comply with Table 9.15.3.4. (2) Where the supported joist span exceeds 4.9 m in buildings with light wood frame walls, floors and roofs, footing widths shall be determined according to, (a) Section 4.2., or (b) the following formula: W = w • [∑ sjs / (storeys • 4.9)] where, W =minimum footing width, w =minimum width of footings supporting joists not exceeding 4.9 m, as defined by Table 9.15.3.4., ∑ sjs =the sum of the supported joist spans on each storey whose load is transferred to the footing, and storeys =number of storeys supported by the footing. (3) Where a foundation rests on gravel, sand or silt in which the water table level is less than the width of the footings below the bearing surface, (a) the footing width for walls shall be not less than twice the width required by Sentences (1) and (2), and Articles 9.15.3.5. and 9.15.3.6., and (b) the footing area for columns shall be not less than twice the area required by Sentences (1) and (2), and Article 9.15.3.7.

(1) The strip footing widths for exterior walls shown in Table 9.15.3.4. shall be increased by, (a) 65 mm for each storey of masonry veneer over wood frame construction supported by the foundation wall, (b) 130 mm for each storey of masonry construction supported by the foundation wall, and (c) 150 mm for each storey of flat insulating concrete form wall construction supported by the foundation wall.

(1) The minimum strip footing widths for interior loadbearing masonry walls shown in Table 9.15.3.4. shall be increased by 100 mm for each storey of masonry construction supported by the footing. (2) Footings for interior non-loadbearing masonry walls shall be not less than 200 mm wide for walls up to 5.5 m high and the width shall be increased by 100 mm for each additional 2.7 m of height.

(1) The footing area for column spacings other than shown in Table 9.15.3.4. shall be adjusted in proportion to the distance between columns.