Canada Footing Sizes (NBC 9.15)

The requirement

The footing is the wide concrete pad at the bottom of your foundation. It spreads the weight of the house out over the ground so the building doesn’t sink. In Canada, the National Building Code (NBC) 2020, Part 9, Section 9.15, gives you the footing sizes straight — no soil test needed — as long as you’re on good, stable ground.

When the simple tables work. These prescriptive 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). If your soil is weaker than that, your spans are long, or the loads are heavy, you’re off the table and into engineered design — see the “not on this website” note below.

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, 130 mm per storey for full masonry, and 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 out over an area, so it’s sized by area, not width. At columns spaced 3 m apart, the minimum footing area is 0.4 m² for 1 floor, 0.75 m² for 2 floors, and 1.0 m² for 3 floors (Table 9.15.3.4). Different spacing scales the area up or down (Art. 9.15.3.7).

Thickness. A footing must be at least the greater of 100 mm, or the distance it projects out 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. 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’s no minimum depth. On clay, or soil that isn’t clearly defined, a heated basement or crawl space foundation goes at least 1.2 m below finished grade (Table 9.12.2.2).

NBC 2020 · Part 9.12 (foundation depth) & 9.15 (footings)

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 must go below the depth of frost penetration — and that depth is set locally, by your 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 volume of concrete 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 = length × width × thickness:

40 × 0.35 × 0.2 = 2.8 m³

So you’d order about 2.8 cubic metres, then add 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

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.

Frequently asked questions

What is the minimum footing width for a house in Canada?

For a light wood-frame house on good soil, the NBC 2020 sets the minimum strip footing width by how many floors sit on the wall. An exterior wall footing is 250 mm wide for 1 floor, 350 mm for 2 floors and 450 mm for 3 floors (Table 9.15.3.4). Interior loadbearing walls are 200 mm, 350 mm and 500 mm for 1, 2 and 3 floors. These only apply on stable soil that can carry 75 kPa or more.

How thick does a footing have to be?

At least the greater of 100 mm, or the width the footing sticks out past the wall or column it holds up (Art. 9.15.3.8). So if your footing projects 120 mm past the wall on each side, it needs to be at least 120 mm thick, not 100 mm. Read the projection off your plan.

How deep does a foundation go in Canada?

It depends on the soil. On rock or coarse, well-drained soils there is no set minimum depth. On clay or soils that aren't clearly defined, a heated basement or crawl space foundation goes at least 1.2 m below finished grade (Table 9.12.2.2). But for unheated foundations or frost-prone ground, there is no national number — you go below the local frost line, which your authority sets.

Does the NBC apply everywhere in Canada?

No. The National Building Code is a model code with no legal force on its own. It only becomes law when a province or territory adopts it, often with changes — BC, Ontario, Alberta and Quebec all run their own editions. Always confirm the code and edition your local authority enforces before you dig.

What if my soil is weak or my spans are long?

Then the prescriptive tables don't apply. If the soil carries less than 75 kPa, joist spans are over 4.9 m, or live loads are over 2.4 kPa, the footing has to be engineered to NBC Part 4 (Art. 9.15.1.1). Buildings on permafrost and permanent wood foundations also fall outside Section 9.15.