The Ontario Building Code | Stairs
3.4.7.5. Stairs
(1) Stairs shall be inclined at an angle of not more than 45° with the horizontal, and their steps shall have risers not more than 210 mm high and treads not less than 220 mm wide exclusive of nosing.
(2) Stairway headroom shall be not less than 1 950 mm plus the height of one riser measured vertically above the nosing of any tread or platform.
(3) The width of a fire escape shall conform to Articles 3.4.3.1., 3.4.3.2. and 3.4.3.4., except that the width is permitted to be reduced to 550 mm provided the fire escape serves,
(a) not more than 3 storeys, and
(b) not more than 15 persons.
(4) If a flight of stairs leading to the ground at the foot of a fire escape is not fixed in position, it shall,
(a) be held in the raised position without a latch or locking device,
(b) be fitted with a counterbalancing device,
(c) be easily and quickly brought into position for use, and
(d) reach the ground in the lowered position.
In Plain Language
Fire escape stairs can't be steeper than 45 degrees, must have risers no taller than 210 mm and treads no narrower than 220 mm, and need at least 1,950 mm of headroom plus one riser height above any tread or platform.
This is a plain-language summary of the 2012/2017 Ontario Building Code text above, for general understanding only and not a substitute for the Code. Always confirm current requirements against the 2024 edition (O.Reg. 163/24) or a qualified professional before construction.