Uniformity and Tolerances for Risers and Treads

(1)  Except as provided in Sentence (2), risers shall be of uniform height in any one flight with a maximum tolerance of,

(a)  5 mm between adjacent treads or landings, and               

(b) 10 mm between the tallest and shortest risers in a flight.


(2)  Except for required exit stairs, where the top or bottom riser in a stair adjoins a sloping finished walking surface such as a garage floor, driveway or sidewalk, the height of the riser across the stair shall vary by not more than 1 in 12.

(3)  Rectangular treads shall have uniform run with a maximum tolerance of,

    (a)   5 mm between adjacent treads, and

    (b)   10 mm between the deepest and shallowest treads in a flight.

(4)  Tapered treads in a flight shall have a uniform run in accordance with the tolerances described in Sentence (3) when measured at a point 300 mm from the centre line of the inside handrail.

(5)  The slope of treads shall not exceed 1 in 50.

Article Ontario Regulation 332/12 Building Code,   Information published by oncodes.ca for educational purposes only.