The requirement
On good soil, an exterior wall footing for a light wood-frame house is 250 mm wide for 1 floor (NBC 2020, Table 9.15.3.4). It goes to 350 mm for 2 floors and 450 mm for 3. Thickness is at least 100 mm. On clay, a heated basement or crawl space goes at least 1.2 m below finished grade.
The footing is the wide concrete pad at the bottom of your foundation. It spreads the weight of the house so the building doesn’t sink. The National Building Code (NBC) 2020, Part 9, Section 9.15, gives you the sizes straight. No soil test needed, as long as you’re on good, stable ground.
When the simple tables work. These sizes only apply to houses and small buildings on stable soil that can carry 75 kPa or more (Art. 9.15.1.1). The footing has to sit on undisturbed soil, rock, or compacted granular fill (Art. 9.15.3.2). Weaker soil, long spans or heavy loads take you off the table. The footing then has to be engineered instead.
Strip footing widths. For a light wood-frame house, the minimum width goes up with the number of floors carried by the wall (Table 9.15.3.4).
| Floors carried | Exterior wall | Interior loadbearing wall |
|---|---|---|
| 1 floor | 250 mm | 200 mm |
| 2 floors | 350 mm | 350 mm |
| 3 floors | 450 mm | 500 mm |
Those are the widths for wood frame. Heavier walls need more. Add 65 mm per storey for masonry veneer. Add 130 mm per storey for full masonry. Add 150 mm per storey for insulated concrete forms (ICF) (Art. 9.15.3.5).
Column (pad) footings. A footing under a column carries a load spread over an area. So it’s sized by area, not width. At columns spaced 3 m apart, you need 0.4 m² of footing for 1 floor (Table 9.15.3.4). You need 0.75 m² for 2 floors and 1.0 m² for 3. Different spacing scales the area up or down (Art. 9.15.3.7).
Thickness. A footing must be at least 100 mm thick. It must also be at least as thick as the distance it projects past the wall or column it supports (Art. 9.15.3.8). So the more your footing sticks out, the thicker it has to be.
Watch the water table. This one bites on gravel, sand or silt. If the water table sits within one footing-width of the bearing surface, the required width doubles (Art. 9.15.3.4). Check your plan.
How deep? That’s a different section, 9.12. On rock or coarse, well-drained soils there is no minimum depth. On clay, or soil that isn’t clearly defined, the bar is 1.2 m. A heated basement or crawl space foundation goes at least that far below finished grade (Table 9.12.2.2).
- 1 footing
- 2 reinforcement
- 3 ground
What is NOT on this website — the frost line. For an unheated foundation, or frost-prone ground with poor drainage, the NBC gives no national depth number. Table 9.12.2.2 just says the foundation goes below the depth of frost penetration. That depth is set locally, by your building authority, off regional climate data. Winnipeg is deeper than Vancouver. Don’t guess it, and don’t copy a number from another town. Ask your building department for the local frost depth.
Work it out on site
The footing sizes are code. The concrete volume you order is just maths, and it feeds straight into the calculator. Say you’re pouring the strip footing for a two-storey wood-frame house. These are example numbers. Your real sizes come off the plan:
- Total perimeter of footing: 40 m
- Footing width (2 floors, exterior): 0.35 m
- Footing thickness: 0.2 m
Volume is length times width times thickness. Here that is 40 × 0.35 × 0.2 = 2.8 m³.
So you’d order about 2.8 cubic metres, plus a bit for spillage and an uneven trench bottom. Most crews tack on 5 to 10 per cent. Swap in your own numbers and the calculator does the sum for you.
Do it in 5 seconds
Related
- Part of the building codes for Canadian trades — the hub, with the province-by-province adoption tracker.
- Building the stairs next? See Canada stair and barrier requirements.
- Working out the pour? Use the concrete volume calculator for slabs & footings.
Sources
- NBC 2020, Division B, Part 9 “Housing and Small Buildings”, Section 9.15 “Footings and Foundations” — minimum footing widths and column areas (Table 9.15.3.4), wall-type add-ons (Art. 9.15.3.5), thickness (Art. 9.15.3.8), and the 75 kPa soil / undisturbed-bearing conditions (Arts. 9.15.1.1, 9.15.3.2). Verified against the official BC government reproduction of NBC Part 9 at free.bcpublications.ca.
- NBC 2020, Section 9.12 “Excavation”, Art. 9.12.2.2 and Table 9.12.2.2 — minimum foundation depth below grade (no limit on rock/coarse soils; 1.2 m on clay/undefined soils; below the local frost line for unheated/frost-prone cases). See free.bcpublications.ca.
- Adoption caveat. Canada has no single, directly-enforceable national building code. The NBC 2020 is a model code published by the National Research Council; it becomes law only when a province or territory adopts it, usually with amendments — the BC Building Code, Ontario Building Code, Alberta Edition and Quebec’s own code all differ. The exact values above are cited from the official BC government reproduction of NBC Part 9, which repeats Sections 9.15 and 9.12 word-for-word; these numbers have been stable for decades and match the NBC-2020-based BCBC 2024. Always confirm the edition and any amendments your local authority enforces before you build.
Related building rules
More Canada rules