London By-law CP-24, s. 4.5.9.3 — Stairs – Non-residential The stair tread rise and run for non-residential stairs shall not exceed these dimensions

Stairs – Non-residential The stair tread rise and run for non-residential stairs shall not exceed these dimensions;

• a) rise minimum 125 mm (5") maximum 200 mm (8")
• b) minimum run of 230 mm (9"), must be uniform
• c) if run is less than 240 mm (9 ½”), a 25 mm (1") nosing is required
• d) existing winders of not more than 3 in 90 degrees and not more than 1 set between floors are permitted and where each tread is not less than 30 degrees and each tread are not greater than 45 degrees.