Footing Depth and Frost Protection in Ontario

In short: in Toronto and most of the GTA, footings for a heated house are typically placed about 1.2 metres (4 feet) below finished grade so frost can’t lift them. The Ontario Building Code sets the minimums, and your engineer’s drawings set the actual depth.

Why footings go below the frost line

When wet soil freezes, it expands and can lift whatever sits on it. Then it thaws and settles. A footing that sits above the frost line moves every winter, and the walls and house above crack. Placing the footing below the depth frost reaches stops that.

How deep is the frost line in Toronto?

Footings for heated buildings in Toronto are typically about 1.2 metres (4 feet) below finished grade. The exact requirement depends on the soil, the drainage and whether the building is heated, and your structural drawings set it for your house.

When footings can be shallower

• When the foundation is protected with rigid insulation designed for frost protection.
• When the footing sits on rock that frost won’t affect.
• When the engineer designs it for the specific soil and building.

Unheated structures, like a detached garage or a deck, follow different rules, so check your drawings.

Who checks the depth?

The City inspects footings before the concrete is poured. The inspector checks the depth, the soil, the size and the reinforcing against the permit drawings. We book that inspection and pour only after it passes.

Questions people ask

Do deck and porch piers need to go below frost?

Usually, yes, so they don’t heave. Our guide to strip, pad and pier footings explains the types.

Can footings be poured in winter?

Yes, with care. The ground under the footing must not be frozen when it’s poured, and the concrete is heated and covered while it cures.

Need footings formed and poured?

See our footings and piers page, or send us your drawings. Get a free quote or call (416) 785-7838.