What's the tallest riser allowed on stairs inside an Ontario house?

For private stairs within a dwelling unit, the tallest riser the 2024 Ontario Building Code allows is 200 mm, measured nosing to nosing.

The minimum is 125 mm, so every riser in the flight has to land between those two numbers. The Code also requires that no two adjacent risers differ by more than 5 mm, and no two risers anywhere in the same flight differ by more than 10 mm. That uniformity rule matters as much as the maximum, because an inconsistent riser is what catches a foot.

If you are rebuilding or replacing a stair, the full set of numbers applies: rise, run, headroom, width, stringer depth and tread thickness all come together. A new or rebuilt interior stair does not appear on either of the City of Ottawa's permit lists, so the right step is to ask the City whether your specific project needs one before work starts.