Carpentry Help for Ottawa Homes, From the Stairs to the Walls

Stairs inside a house: the Code numbers

1. 1

   Rise: 125–200 mm

   Each riser between 125 mm and 200 mm, measured as the vertical distance from nosing to nosing.

   Table 9.8.4.1.; 9.8.4.1.(1)

2. 2

   Run: 255–355 mm

   Each run (rectangular treads) between 255 mm and 355 mm.

   Table 9.8.4.1.

3. 3

   Headroom: ≥ 1 950 mm

   Clear height over stairs serving a single dwelling unit not less than 1 950 mm, measured from a straight line tangent to the tread and landing nosings to the lowest point above.

   9.8.2.2.(1) and (3)

4. 4

   Handrail height: 865–1 070 mm

   Required handrails 865 mm to 1 070 mm high, measured vertically from a straight line drawn tangent to the tread nosings. Inside a dwelling unit, a stair narrower than 1 100 mm needs a handrail on one side; interior stairs with not more than 2 risers need none.

   9.8.7.4.(1)–(2); Table 9.8.7.1.; 9.8.7.1.(3)(a)

5. 5

   Guard height: ≥ 900 mm

   Inside a dwelling unit, guards not less than 900 mm high. A guard is required on an open side where the drop to the surface within 1.2 m is more than 600 mm. On a stair, guard height is measured to a line drawn through the tread nosings.

   9.8.8.3.(2) and (4); 9.8.8.1.(1)

6. 6

   Guard openings: 100 mm sphere

   Openings in a guard must stop a 100 mm sphere from passing through. The triangle under a stair guard (riser, tread and bottom rail) must stop a 150 mm sphere.

   9.8.8.5.(1)–(2)

7. 7

   Width: ≥ 860 mm

   At least one stair between each floor level within a dwelling unit not less than 860 mm wide. Width is measured across the stair, so it does not show in a side view.

   9.8.2.1.(4)

Clause numbers are from the January 2025 compendium. Check with the City before you rely on one. Source: Ontario Building Code 2024 (O. Reg. 163/24), 2024 Building Code Compendium, January 16, 2025 update.