Why Frost Depth Footings Aren't the Same Number Everywhere in Canada

Frost depth — how far into the ground the soil actually freezes in a typical winter — varies hugely across the country, and footings need to sit below that line so the freeze-thaw cycle doesn't lift them. A mild coastal climate might need less than half a metre; a cold interior or prairie location can require well over a metre.

This is one of the clearest examples of why "the code" isn't one universal number. Provinces and municipalities publish their own frost depth requirements based on local climate data, and it's one of the first things worth confirming with your local building department before you dig a single footing.