Canada Stair Building Code

Canadian Stair Building Code

includes stair dimensions, configurations, and step dimensions described in

BC Building Code 2012 and Ontario Building Code 2012.

9.8.2. Stair Dimensions

9.8.2.1. Stair Width

1) Except as provided in Sentence (2), required exit stairs and public stairs serving buildings of residential occupancy shall have a width of not less than 900 mm.

2) Exit stairs serving a single dwelling unit shall have a width of not less than 860 mm.

3) Required exit stairs and public stairs serving buildings of other than residential occupancy shall have a width of not less than the greater of

a) 900 mm, or
b) 8 mm per person based on the occupant load limits specified in Table 3.1.17.1.

4) At least one stair between each floor level within a dwelling unit, and exterior stairs serving a single dwelling unit except required exit stairs shall have a width of not less than 860 mm.

9.8.2.2. Height over Stairs

1) The clear height over stairs shall be measured vertically, over the clear width of the stair, from a straight line tangent to the tread and landing nosings to the lowest point above. (See Note A-3.4.3.4.)

2) Except as provided in Sentence (3), the clear height over stairs shall not be less than 2 050 mm.

3) The clear height over stairs serving a single dwelling unit shall not be less than 1 950 mm.

9.8.3. Stair Configurations

Minimum dimensions for all stair types have been increased in the BCBC 2018. The Code distinguishes three principal types of treads:rectangular, tapered (previously referred to as angled) and winders, as shown below. Spiral stairs (i.e. multiple steps that rotate about a tight axis turning greater than 90°) are not compliant with BCBC 2018.

Definitions:

› Flight: a series of steps between landings.

› Run: the horizontal distance between two adjacent tread nosings on a stair.

› Tapered tread: a tread with non-parallel edges that increases or decreases its run uniformly over its width. The definition of tapered tread includes treads in curved stairs and treads in winder stairs. However, requirements for winders differ from those for other tapered treads. All tapered treads and winders within a curved flight must turn in the same direction.

› Private Stairs: exterior or interior stairs that serve single dwelling units or that serve garages that serve single dwelling units.

› Public Stairs: all stairs not described as service stairs or private stairs.

9.8.3.1. Straight and Curved Runs in Stairs

(1) Except as provided in Sentence (2), stairs shall consist of,

(a) straight-runs, or

(b) curved-runs.

(2) Stairs within dwelling units shall consist of,

(a) straight-runs,

(b) curved-runs,

(d) straight-runs with curved-runs

9.8.3.2. Minimum Number of Risers

1) Except for stairs within a dwelling unit, at least 3 risers shall be provided in interior flights.

9.8.3.3. Maximum Height of Stairs

1) The vertical height of any flight of stairs shall not exceed 3.7 m

9.8.4. Step Dimensions

9.8.4.1. Dimensions for Risers

1) Except for stairs serving areas only used as service rooms or service spaces, the rise, which is measured as the

vertical nosing-to-nosing distance, shall comply with Table 9.8.4.1.

9.8.4.2. Dimensions for Rectangular Treads (Straight Flight)

The required rise and run dimensions have changed for stairs as listed in Table 9.8.4.2. and shown below. The dimensions

shown below also apply to some tapered treads. The changes of dimensions reflect current research on stair safety

9.8.4.3. Dimensions of Tapered Treads

Tread dimensions for tapered treads are set to ensure minimum

and maximum run dimensions at the walking line. Tapered treads

must have a run that is not less than 150 mm at the narrow end of

the tread and comply with the dimensions stated in Table 9.8.4.2.

(see previous page) when measured at a point 300 mm from the

centre line of the handrail at the narrow end of the tread.

9.8.4.4. Uniformity and Tolerances for Risers and Treads

(1) Except as provided in Sentence (2), risers shall be of uniform height in any one flight with a maximum tolerance of,

(a) 5 mm between adjacent treads or landings, and

(b) 10 mm between the tallest and shortest risers in a flight.

(2) Except for required exit stairs, where the top or bottom riser in a stair adjoins a sloping finished walking surface such as a garage floor, driveway or sidewalk, the height of the riser across the stair shall vary by not more than 1 in 12.

(3) Treads shall have uniform run with a maximum tolerance of,

(a) 5 mm between adjacent treads, and

(b) 10 mm between the deepest and shallowest treads in a flight.

(4) Where angled treads or winders are incorporated into a stair, the treads in all sets of angled treads or winders within a flight shall turn in the same direction.

(5) The slope of treads shall not exceed 1 in 50.

9.8.4.5. Winders

(1) Stairs within dwelling units are permitted to contain winders that converge to a centre point provided,

(a) the winders turn through an angle of not more than 90°,

(b) individual treads turn through an angle of not less than 30° or not more than 45°, and

(2) Where more than one set of winders described in Sentence (1) is provided in a single stairway between adjacent floor levels, such winders shall be separated in plan by at least 1 200 mm.

9.8.4.6. Leading Edges of Treads

(1) Leading edges of treads that are bevelled or rounded shall,

(a) not reduce the required tread depth by more than 15 mm, and

(b) not, in any case, exceed 25 mm horizontally.

9.8.4.7. Interior Stairs Extending through the Roof

(1) Interior stairways extending through the roof of a building shall be protected from ice and snow.

9.8.4.8. Tread Nosings

(See Notes A-9.8.4.8. and A-9.8.4.)

1) Except as permitted by Sentence (2), the top of the nosings of stair treads shall have a rounded or beveled edge extending not less than 6 mm and not more than 14 mm measured horizontally from the front of the nosing.

2) If resilient material is used to cover the nosing of a stair tread, the minimum extension of the rounded or beveled edge required by Sentence (1) is permitted to be reduced to 3 mm.