Canadian building code question

What are the stair riser and tread requirements under the Canadian building code?

The NBC sets maximum riser heights, minimum tread depths, uniformity tolerances, and nosing requirements that vary by stair type, occupancy, and whether the stair is an exit stair or not. Provincial adoption may amend these dimensions.

Stair geometry is one of the most commonly enforced code provisions because dimensional errors create life-safety risk. The requirements cover riser height, tread depth, uniformity between steps, nosing profile, and how these change for exit stairs, public stairs, and residential stairs. Always confirm the applicable provincial edition before locking stair dimensions.

What to check first

  • Maximum riser height and minimum tread depth depend on whether the stair is an exit stair, a public stair, or a private stair within a dwelling unit.
  • Uniformity tolerances limit the dimensional variation between the largest and smallest riser or tread in a flight.
  • Nosing projection and profile requirements apply to most stairs and affect slip resistance and accessibility.

Jurisdiction notes

National baseline

Start with the NBC stair dimension tables and confirm whether the stair serves as an exit, a public corridor stair, or a private residential stair.

Province and edition check

Some provinces amend riser/tread dimensions or add requirements for specific occupancies. Confirm the adopted edition.

Accessibility overlay

Barrier-free path of travel requirements may impose additional constraints on stair geometry, nosing contrast, and tactile indicators.

Work through it in this order

  1. Classify the stair type: exit stair, public stair, or private residential stair.
  2. Look up the applicable riser height and tread depth limits in the NBC for that stair type.
  3. Verify uniformity tolerances and nosing requirements.
  4. Check provincial adoption for any amendments to the national baseline dimensions.

Common questions

What is the maximum riser height for an exit stair?

The NBC sets a maximum riser height for exit stairs that is typically stricter than for private stairs. The exact value depends on the code edition and provincial adoption — verify the cited provision.

Do residential stairs have different tread requirements?

Yes. Private stairs within dwelling units generally allow a smaller minimum tread depth and higher maximum riser than public or exit stairs.

What uniformity tolerance applies between risers?

The code limits the difference between the largest and smallest riser in a flight. The exact tolerance depends on the code edition — confirm with the cited provision.