The Ontario Building Code | Dimensions for Angled Treads
220.127.116.11. Dimensions for Angled Treads
(1) Angled treads in required exit stairs shall conform to the requirements in Article 18.104.22.168.
(2) Except as provided in Article 22.214.171.124., angled treads in other than required exit stairs shall have an average run, which is measured as the horizontal nosing-to-nosing distance, of not less than 200 mm and a minimum run of 150 mm.
(3) The depth of an angled tread shall be not less than its run, measured as the horizontal nosing-to-nosing distance, at any point and not more than its run at any point plus 25 mm.