Canada Footing Sizes (NBC 9.15)

The requirement

This is the NBC 2020 model-code baseline. Check the edition and changes in force in your province or territory before using it.

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 and depth have separate checks. Read the projection rule and the soil, drainage and heating conditions below.

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. Confirm the ground conditions and table scope before choosing a size.

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). Weak soil and unusual loads need further design checks. For long joists, Article 9.15.3.4(2) gives an adjustment formula or a Section 4.2 design route.

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).

Those are the basic widths. Exterior wall footings need added width for heavier walls under Article 9.15.3.5. Add 65 mm per supported storey of masonry veneer, 130 mm for masonry, or 150 mm for flat ICF walls. Interior loadbearing masonry uses a separate 100 mm addition per storey under Article 9.15.3.6.

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 wall-footing width doubles. Column-footing area doubles too (Art. 9.15.3.4). Check your plan.

Depth depends on more than soil type. Table 9.12.2.2 separates heated and unheated foundations, soil type and drainage. Insulation that reduces heat flow beneath the footing moves the design to the unheated conditions.

For clay or undefined soils, the heated-space table starts at 1.2 m. The unheated case needs at least 1.2 m and not less than frost depth. Other soils have different table entries. Article 9.12.2.2 also has exceptions for certain structures and designs. Get the project depth from the plan.

1. 1 footing
2. 2 reinforcement
3. 3 ground

The local frost depth is a site input. Do not copy it from another town. Check it with the ground report and the building authority.

Work it out on site

For the volume calculation, use the concrete element’s thickness from the approved drawings. This is different from its embedment below ground level. Calculate separate concrete walls or beams separately, without double-counting intersections.

The plan sets the concrete sizes. The volume you order comes from maths and 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. Agree the extra amount with the supplier. 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 official second printing, Volume 2, §§9.12.2 and 9.15.1–9.15.3. Direct text checked 6 September 2026; includes 31 March 2025 errata.
• Check provincial adoption and changes before using this model-code baseline. Table scope, soil, water, wall type, spans and heating all matter. A quantity example is not a footing design.