How deep do footings need to be for an addition in Ottawa?

Footings for an addition in Ottawa are commonly founded about 1.5 m deep to get below frost. The exact depth depends on the soil and the design, and where the ground includes Champlain Sea clay, which has to be addressed for most development built on it, we confirm site conditions before finalizing the foundation design.

A floating slab without frost-depth footings only suits light, unheated structures. A heated, four-season room or a habitable addition needs footings below frost, or frost heave can crack the floor and rack the windows within a few winters. For an example, see our recent single-storey addition on a new slab in Greely.