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OBC DIVISION B · PART 3 · SECTION 3.4 — EXITS

What are the required dimensions for exit stairs under the Ontario Building Code?

Exit stairs generally need at least 1 100 mm clear width, risers no more than 180 mm, runs at least 280 mm, landings as long as the stair width, about 2 050 mm headroom, and handrails at 865 mm to 1 070 mm height.

Code reference
Exit stairs must meet minimum width based on the greater of the fixed minimum and the occupant-load calculation, with uniform risers and runs within prescribed maximums and minimums, landings at required intervals and at doors, minimum headroom, and handrails and guards meeting height, graspability and continuity requirements.
OBC Division B, Subsection 3.4.3.

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

What this means in practice

Set riser and run geometry early because floor-to-floor heights rarely divide neatly, and non-uniform steps are a rejection item. Confirm that door swings onto landings do not reduce landing depth below the required clear dimension, that handrail projections stay within permitted encroachment, and that guards meet height and climbability rules. In high buildings and care occupancies additional stair provisions apply, and barrier-free and Fire Code retrofit considerations can layer on further requirements.

Plain language

Escape stairs must be wide enough for two streams of people, with steps that are all the same comfortable size, sturdy handrails on both sides, good headroom, and flat landings where the doors open.

Related questions

When are two exits required from a floor area in Ontario?How is required exit width calculated under the Ontario Building Code?How many exits does a floor area need under the Ontario Building Code?

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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.