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OBC DIVISION B · PART 9 · SECTION 9.8 — STAIRS, RAMPS, HANDRAILS AND GUARDS

How high must a deck guard or railing be in Ontario?

Guards are required where the walking surface is more than 600 mm (24 in) above ground. Residential guards must be at least 900 mm (35 in) high, increasing to 1,070 mm (42 in) where the deck is more than 1.8 m above grade.

Code reference
A guard is required at the open sides of walking surfaces, including decks and landings, more than 600 mm above the adjacent level. Within dwellings, minimum guard height is 900 mm, increasing to 1,070 mm where the fall exceeds 1.8 m. Openings must prevent passage of a 100 mm sphere, and guards must not facilitate climbing.
OBC Division B, Subsection 9.8.8.

Paraphrased for clarity — open this provision in the BUILDAiD Library for the exact wording.

What this means in practice

The 100 mm sphere rule governs baluster spacing: with typical deflection, install pickets at about 95 mm clear or less to pass. The climbability provision restricts horizontal elements between 140 mm and 900 mm above the deck that could act as a ladder, so horizontal cable and mid-rail designs need care. Stair guards inside dwellings can be 900 mm above nosings. Structural attachment is the biggest real-world failure: guard posts must resist significant lateral loads, so bolt them properly rather than nailing to the rim board.

Plain language

Any deck more than 600 mm off the ground needs a railing: at least 900 mm high, or 1,070 mm once you are more than 1.8 m up. Gaps must be small enough that a 100 mm ball can't pass through.

Related questions

What is the maximum stair rise and minimum run in Ontario?What height must a stair handrail be in Ontario?

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This page is provided for general information. Building code requirements depend on your specific project, occupancy and municipality, and code editions change. Always verify requirements against the current Ontario Building Code and confirm with your local building department.