Deck Footings & Helical Piles

For deck foundations with no heated space in clay or soils not clearly defined, the Building Code table sets a depth of 1.2 m, but not less than the depth of frost penetration, and Ontario says frost depth is established on the basis of local experience. We found no City of Ottawa page that sets one frost depth for decks, so ask the builder and your permit reviewer what depth your drawings show and why.

Some decks are exempt from those depths: a deck of not more than 1 storey and not more than 55 square metres, with no more than 600 mm from finished ground to the underside of the joists, not supporting a roof, and not attached to another structure unless it can be shown that differential movement will not adversely affect that structure. All five conditions have to hold.

Ontario adds two rules that matter here. Where a foundation is on filled ground, peat or sensitive clay, including Leda clay, the footing sizes must be designed under Section 4.2 of the Code, and deep foundations also go to Section 4.2 design. The City's permit list includes a helical pile layout and specifications where piles are used. Before anyone digs, Ontario law says the excavator, which includes a homeowner digging their own holes, must request a free locate through Ontario One Call; members have 5 business days to respond. Too few published Ottawa footing prices exist to quote a range.