Canadian building code question

What are the building code requirements for deck footings and foundations in Canada?

Deck footings must extend below frost depth, be sized for the soil bearing capacity and tributary load, and use appropriate materials. The requirements vary by deck size, height, attachment to the house, and local soil and climate conditions.

Deck foundation failures are common and preventable. The building code requires footings to extend below the frost line to prevent heaving, be sized based on the tributary load and soil bearing capacity, and use durable materials. The specific frost depth varies significantly across Canada. Whether the deck is attached to the house or freestanding affects the foundation design and ledger connection requirements.

What to check first

  • Footings must extend below the local frost depth to prevent frost heaving.
  • Footing size depends on the tributary load from the deck and the soil bearing capacity.
  • Attached decks require proper ledger connections to the house structure in addition to footings.

Jurisdiction notes

National baseline

The NBC sets frost depth protection, soil bearing, and structural requirements for deck foundations.

Local frost depth

Frost depth varies significantly across Canada and is specified in the climatic data tables or by the local authority.

Municipal requirements

Some municipalities set specific footing size minimums or require engineered foundations for larger decks.

Work through it in this order

  1. Determine the frost depth for your location from climatic data tables or the local building department.
  2. Calculate the tributary load for each footing based on the deck design and expected loads.
  3. Size footings based on the tributary load and the assumed or tested soil bearing capacity.
  4. If the deck is attached, design the ledger connection to the house per the applicable provisions.

Common questions

How deep do deck footings need to be?

Footings must extend below the local frost depth, which varies from about 1.2 m to over 2.4 m depending on location in Canada.

Can I use sonotubes for deck footings?

Sonotubes (concrete form tubes) are commonly used for deck footings when properly sized and extended below frost depth.

Does a freestanding deck need different footings?

Freestanding decks have the same footing depth and sizing requirements but do not need a ledger connection to the house.