The Ontario Building Code | Basic Footing Widths and Areas

9.15.3.4. Basic footing Widths and Areas

(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.

Table 9.15.3.4.
Minimum footing Sizes

Forming Part of Sentence 9.15.3.4.(1)

Item	Column 1	Column 2	Column 3	Column 4
	Number of floors supported	Minimum Width of Strip footings, mm		Minimum footing Area for columns Spaced 3 m o.c.(1), m2
		supporting Exterior walls(2)	supporting Interior walls(3)
1.	1	250	200	0.40
2.	2	350	350	0.75
3.	3	450	500	1.0

Notes to Table 9.15.3.4.:

⁽¹⁾ See Sentence 9.15.3.7.(1).

⁽²⁾ See Sentences 9.15.3.5.(1).

⁽³⁾ See Sentence 9.15.3.6.(1).

(2) Where the supported joist span exceeds 4.9 m in buildingswith 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.