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OBC DIVISION B · PART 3 · SECTION 3.4 — EXITS

When can exterior stairs be used as exits under the Ontario Building Code?

Exterior stairs can serve as required exits for lower buildings where they lead directly to ground level and are protected from fire exposure, meaning nearby windows and doors that could expose the stair must be limited or protected. Fire escapes are restricted to existing buildings.

Code reference
Exit stairs located outside the building must discharge to ground level, meet the same dimensional, guard and handrail rules as interior exit stairs, and be protected from openings in the adjacent building face that could expose people using the stair to fire, with limits tied to building height and occupancy. Traditional fire escapes are permitted only on existing buildings under restricted conditions.
OBC Division B, Subsection 3.4.6.

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

What this means in practice

Exterior egress stairs are popular on walk-ups, schools and additions because they free interior floor area, but the exposure-protection requirement is the usual sticking point: unprotected windows near the stair within the prescribed zone need wired glass, rated closures or relocation. Consider Ontario winters as well, since snow and ice on open stairs create real liability, and check guard heights, riser uniformity and illumination just as for interior stairs.

Plain language

An outdoor staircase can count as a real exit on smaller buildings if it runs straight down to the ground and no windows nearby could blast it with flames. Old-style metal fire escapes are only allowed on existing buildings.

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.