Hardwood stairs and Ontario Building Code

Pretty is not the test

Ontario Building Code Part 9 governs most houses. Rise and run must be uniform. Nosing projection is limited. Guards have a height. Handrails must be graspable. A 2x6 cap with no fingers-around profile will fail. A rail mounted on the wrong side of a winders flight will fail. Draw the stair to pass, then make it beautiful.

The numbers, and where they interact

Rise must not exceed 200 mm on a stair serving a dwelling unit. Run must be at least 210 mm. Tread depth — run plus nosing projection, not run alone — must be at least 235 mm, and the nosing itself may project no more than 25 mm.

Where a flight has 3 or more risers a handrail is required, between 865 mm and 965 mm above the nosing line, with a circular profile graspable between 30 mm and 45 mm in diameter. Guards at the side of a dwelling stair are at least 900 mm from the nosing line.

These interact, which is what people miss. A retread adds thickness to every tread, which does not change the rises in the middle of the flight but does change the first and last ones — and the finished floor heights at the top and bottom change them again. Those two risers are where most conversions go out of tolerance.

The stair studio on this site checks a flight against these limits. It will not certify your stair — no tool can, and a building official is the only authority — but it will tell you which dimension is the problem before anyone quotes.

Uniformity is a rule, not a preference

A flight where every riser is inside the limit but one is noticeably taller than its neighbours is still a flight people trip on, and the variation between the tallest and the shortest in a run is itself limited.

This is the reason a stair quote should follow a measurement of every riser, not a step count over the phone. In a house from the 1950s, stringers cut by eye are common and the answer is sometimes that the flight cannot be retreaded and needs rebuilding.

The conversions that go wrong

Carpet to oak on an open-side stair needs returned treads, not a leftover plank glued to drywall. Mixing a 3/4" floor with a 5/8" tread without a proper nosing creates a trip. We see both weekly in new builds from Milton to Markham.

The other common one is the rail. Once a stair is altered, the argument that the old railing was compliant when the house was built gets thin — and a rail that was never graspable was never compliant anyway.

Railings are structural

A newel that is only trimmed on is a future service call. Through-bolt newels into structure. If that is not possible, rebuild the landing until it is. That is the difference between a railing and furniture.

A guard has to resist a real lateral load — someone falling against it, not leaning on it. Fixing it to drywall and hoping is the failure mode that matters, because it fails at the moment it is needed.