Canadian building code question

What minimum stair width is required by the Canadian building code?

For the exit-stair focus of this page, the minimum width depends on the occupant load served, the stair's role in the egress system, and how the province adopts or amends the baseline NBC provisions. Other stair conditions, including some residential interior stairs and non-exit stairs, can follow a different width path.

Stair width is rarely one number. This page is intentionally focused on exit stairs in Part 3 buildings because they are a common source of plan-review questions and layout rework. The safest workflow is to confirm that the stair is actually being treated as an exit stair first, then check how occupant load and project conditions affect the required width.

What to check first

  • Identify the stair's function first. This page is about exit stairs in Part 3 buildings, and other stair conditions can have different width requirements.
  • Occupant load can increase the required width beyond the code minimum. Do not treat the minimum as a universal safe number.
  • Handrail projections and landing conditions can reduce the usable width, so the clear width between handrails matters for compliance.

Jurisdiction notes

National baseline

Start with the NBC means-of-egress provisions covering exit stair width in Part 3 buildings, then confirm the stair's function and the occupant load served.

Province and edition check

Validate provincial adoption and any amendments that may change the exit stair width path, especially for high-occupancy or assembly conditions.

Stair-specific variables

Handrail projections, landing geometry, clear width between handrails, occupant load increases, and the interaction between stair width and other egress requirements can all affect the final compliant dimension.

Work through it in this order

  1. Confirm whether the stair is an exit stair, a public stair, or another condition before selecting the applicable width requirement.
  2. Calculate the occupant load the stair must serve and check whether it increases the required width beyond the code minimum.
  3. Account for handrail projections and landing dimensions to verify the clear width between handrails meets the requirement.
  4. Document the cited width requirement, the occupant load assumption, and the governing sections before finalizing the stair detail.

Common questions

Is there one minimum stair width that applies to every building?

No. The required width depends on the stair's function, the occupant load it serves, and provincial adoption. A high-occupancy exit stair may need to be wider than the base minimum, while other stair types may follow a different code path entirely.

Do handrails affect the required stair width?

Yes. Handrail projections reduce the usable clear width between them. The compliance check should account for the installed handrail condition, not just the wall-to-wall dimension.

Can I use this page for residential interior stairs?

Not directly. This page focuses on exit stairs in Part 3 buildings. Residential interior stairs in houses or small buildings may follow a different code path with different width rules.