London : Règlement no CP-24, art. 4.5.9.1 — Stairs – Interior – Single Dwelling The stair tread rise and run for residential interior single dwelling unit shall not exceed these dimensions

Stairs – Interior – Single Dwelling The stair tread rise and run for residential interior single dwelling unit shall not exceed these dimensions:

• a) maximum rise 230 mm (9")
• b) minimum tread 230 mm (9")
• c) minimum run 200 mm (8")
• d) if run is less than 240 mm (9½”), a 25 mm (1") nosing is required
• e) existing winders of not more than 3 in 90 degree and not more than 2 sets between floors are permitted and where each tread is not less than 30 degrees and each tread is not greater than 45 degrees