Ontario building code question

What are the Ontario Building Code requirements for decks?

Decks in Ontario must comply with the Ontario Building Code for structural loads, guard height and spacing, stair dimensions, ledger connections, footing depth below frost line, and typically require a building permit when attached to a house or elevated above grade.

Deck construction is one of the most common residential permit applications in Ontario. The Ontario Building Code sets requirements for structural design loads, footing depth below the frost line, guard height and baluster spacing, stair rise and run dimensions, ledger board connections to the house, and waterproofing where the deck attaches to the building envelope. Most Ontario municipalities require a permit for any deck attached to a building or elevated more than 0.6 m above grade.

What to check first

  • A building permit is typically required for decks attached to a house or elevated above a specified height.
  • Footings must extend below the frost line, which varies across Ontario from roughly 1.2 m to 1.8 m.
  • Guards must meet minimum height and baluster spacing requirements to prevent falls.

Jurisdiction notes

Ontario Building Code

The OBC adopts NBC requirements with Ontario-specific amendments for residential deck construction, including frost depth by region.

Municipal permit requirements

Most Ontario municipalities require a permit application with a site plan and structural details for deck construction.

Frost depth variation

Footing depth requirements vary across Ontario based on the frost penetration depth for the specific location.

Work through it in this order

  1. Check the municipal permit requirements and setback bylaws for the deck location.
  2. Confirm the frost depth for footing design based on the Ontario location.
  3. Verify structural load requirements for joists, beams, posts, and ledger connections.
  4. Ensure guard height, baluster spacing, and stair dimensions meet OBC requirements.

Common questions

Do I need a permit for a deck in Ontario?

In most municipalities, yes, if the deck is attached to a building or elevated above a specified height, typically 0.6 m above adjacent grade.

How deep do deck footings need to be in Ontario?

Footings must extend below the frost line, which ranges from approximately 1.2 m in southern Ontario to 1.8 m or more in northern regions.

What is the minimum guard height for a deck in Ontario?

The minimum guard height is typically 1070 mm for residential decks, but verify the current OBC requirement for your specific deck height and condition.