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Code guide

Ontario Building Code Stairs: Rise, Run, Width, Headroom and Landings

Ontario Building Code stairs (2024): 125 to 200 mm rise, 255 to 355 mm run, 860 mm width, 1,950 mm headroom, plus nosing, landings and winders.
max rise, stairs in or serving a house
200 mm
max rise, stairs in or serving a house
min run, rectangular treads in a house
255 mm
min run, rectangular treads in a house
min width, at least one stair per floor level
860 mm
min width, at least one stair per floor level
min headroom over house stairs
1,950 mm
min headroom over house stairs

Last updated

Stairs inside or serving a single house in Ontario must have a rise between 125 mm and 200 mm and a run between 255 mm and 355 mm under the 2024 Building Code (OBC Div. B Table 9.8.4.1.OBC Div. B Table 9.8.4.1. Rise for Rectangular Treads, Tapered Treads and Winders and Run for Rectangular Treads — Forming Part of Sentences 9.8.4.1.(1) and 9.8.4.2.(1)Table 9.8.4.1 — Rise for Rectangular Treads, Tapered Treads and Winders and Run for Rectangular Treads — Forming Part of Sentences 9.8.4.1.(1) and 9.8.4.2.(1) Stair Type | Max. Rise, mm, for All Steps | Min. Rise, mm, for All Steps | Max. Run, mm, for Rectangular Treads | Min. Run, mm, for Rectangular Treads Private…). The other key numbers are 860 mm minimum width (9.8.2.1.OBC Div. B 9.8.2.1. Stair Width(1) Except as provided in Sentence (2) and Article 9.8.4.7., 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 or a house with a secondary suite including their common spaces shall have a width of…) and 1,950 mm minimum headroom (9.8.2.2.OBC Div. B 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 Sentences (3) and (4) and Article 9.8.4.7., the clear height over stairs shall not…).

The code calls these "private stairs": interior stairs in a dwelling unit or a house with a secondary suite, exterior stairs serving one, and exterior stairs serving its garage. Everything else, apart from a few service and attic cases, is a "public stair" with stricter numbers. This page paraphrases Part 9 of Division B. Your building department may apply local requirements or permit conditions.

Stair values for houses at a glance

Item Private stair (house) Public stair Article
Rise 125 mm to 200 mm 125 mm to 180 mm Table 9.8.4.1.
Run (rectangular treads) 255 mm to 355 mm 280 mm minimum Table 9.8.4.1.
Tread depth run to run + 25 mm same 9.8.4.2.(2)
Width 860 mm 900 mm (residential) 9.8.2.1.
Headroom over stairs 1,950 mm 2,050 mm 9.8.2.2.
Headroom over landings 1,950 mm 2,050 mm 9.8.6.4.
Riser tolerance 5 mm adjacent, 10 mm in flight same 9.8.4.4.
Nosing round or bevel 6 mm to 14 mm same 9.8.4.8.
Handrail height 865 mm to 1,070 mm same 9.8.7.4.

This is our own summary. The code table also covers service stairs, attic and crawl space stairs, and mezzanines in live/work units, which are not shown here.

Rise and run

Rise is measured nosing to nosing, vertically (9.8.4.1.OBC Div. B 9.8.4.1. Dimensions for Risers(1) Except as provided in Article 9.8.4.7., the rise, which is measured as the vertical nosing-to-nosing distance, shall conform to Table 9.8.4.1.). Run is the horizontal distance the tread advances, and the actual tread depth must be at least the run and not more than the run plus 25 mm (9.8.4.2.OBC Div. B 9.8.4.2. Dimensions for Rectangular Treads(1) The run for rectangular treads shall conform with Table 9.8.4.1. (2) The depth of a rectangular tread shall be not less than its run and not more than its run plus 25 mm.). That 25 mm allowance is the nosing overhang.

Steps in a flight must be uniform. Adjacent risers may differ by no more than 5 mm, and the tallest and shortest riser in a flight by no more than 10 mm. Runs have the same tolerances (9.8.4.4.OBC Div. B 9.8.4.4. Uniformity and Tolerances for Risers, Runs 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…). Where the bottom or top riser meets a sloping surface such as a garage floor or driveway, the riser may vary across its width by up to 1 in 12, except in required exit stairs. Treads may slope no more than 1 in 50.

Width and headroom

At least one stair between each floor level in a dwelling unit, and exterior stairs serving a single dwelling unit, must be at least 860 mm wide (9.8.2.1.(4)OBC Div. B 9.8.2.1. Stair Width(1) Except as provided in Sentence (2) and Article 9.8.4.7., 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 or a house with a secondary suite including their common spaces shall have a width of…). Exit stairs serving a single dwelling unit or a house with a secondary suite also need 860 mm, while exit and public stairs in other residential buildings need 900 mm.

Headroom is measured vertically over the clear width of the stair, from a line tangent to the tread and landing nosings to the lowest point above (9.8.2.2.OBC Div. B 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 Sentences (3) and (4) and Article 9.8.4.7., the clear height over stairs shall not…). Stairs serving a single dwelling unit or a house with a secondary suite need 1,950 mm. Other stairs need 2,050 mm. Under beams and ducting in a secondary suite, 1,850 mm is permitted.

Winders, tapered treads and spiral stairs

Within dwelling units, stairs may be straight, curved, spiral, or include winders or tapered treads (9.8.3.1.OBC Div. B 9.8.3.1. Straight and Curved Runs in Stairs(1) Except as permitted in Sentence (2), stairs shall consist of (a) straight flights, (b) curved flights, or (c) spiral stairs. (2) Stairs within dwelling units and houses with a secondary suite, including their common spaces, shall consist of (a) straight flights, (b) except as provided in Sentence (4), curved…). Winders must converge to a centre point, turn a total of not more than 90 degrees, and each tread must turn between 30 and 45 degrees, with adjacent winders turning the same angle (9.8.4.6.OBC Div. B 9.8.4.6. 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 (c) adjacent winders turn through the same angle. (2) Where…). Tapered treads need at least 150 mm of run at the narrow end and must meet the normal run limits when measured 300 mm from the centre line of the handrail at the narrow end (9.8.4.3.OBC Div. B 9.8.4.3. Dimensions of Tapered Treads(1) Except as provided in Sentence (2) and Articles 9.8.4.6. and 9.8.4.7., tapered treads shall have a run that (a) is not less than 150 mm at the narrow end of the tread, and (b) complies with the dimensions for rectangular treads stated in Table 9.8.4.1. when measured at a point 300 mm from the centre line of the…). Spiral stairs have their own article, 9.8.4.7.

Landings

A landing is required at the top and bottom of each flight, at the top and bottom of steeper ramps, and where a doorway opens onto a stair (9.8.6.2.OBC Div. B 9.8.6.2. Required Landings(1) Except as provided in Sentences (2) to (4) and Sentence 9.9.6.6.(2), a landing shall be provided (a) at the top and bottom of each flight of interior and exterior stairs, including stairs in garages, (b) at the top and bottom of every ramp with a slope greater than 1 in 50, and (c) where a doorway opens onto a…). Two useful exceptions for houses:

  • Inside a dwelling unit, no landing is needed between a door and the top of the stair if the door swings away from the stair.
  • At a secondary entrance to a house, the top landing may be omitted for an exterior stair with not more than three risers, if the main door slides or swings away and only a storm or screen door swings over the stair.

Landings must be at least as wide and as long as the stair width, but a straight-through landing need not be longer than the required stair width or 1,100 mm, whichever is less (9.8.6.3.OBC Div. B 9.8.6.3. Dimensions of Landings (See also Articles 9.9.6.1. and 9.9.6.6. regarding landings in exits)(1) Except as provided in Sentences (2) to (7), landings shall be at least as wide and as long as the width of the stair or ramp in which they occur. (2) Where the landing in a stairway or ramp does not turn or turns less than 90° , the length of the landing need not be more than the lesser of (a) the required width…). A door that swings toward a stair must swing entirely over the landing.

Handrails, guards and open risers

  • Handrails. Required on stairs as set out in Table 9.8.7.1, at 865 mm to 1,070 mm high (9.8.7.1.OBC Div. B 9.8.7.1. Required Handrails(1) Except as provided in Sentences (2) to (4), handrails shall be installed on stairs and ramps in conformance with Table 9.8.7.1. (2) Where a stair or ramp is required to be at least 2,200 mm wide due to the occupant load, a handrail shall be installed such that no position on the stair or ramp is more than 825 mm…, 9.8.7.4.OBC Div. B 9.8.7.4. Height of Handrails(1) The height of handrails on stairs and ramps shall be measured vertically from the top of the handrail to (a) a straight line drawn tangent to the tread nosings of the stair served by the handrail, or (b) the surface of the ramp, floor or landing served by the handrail. (2) Except as provided in Sentence (3)…). See handrail height in Ontario.
  • Guards. Required where the side of a stair has a drop of more than 600 mm (9.8.8.1.OBC Div. B 9.8.8.1. Required Guards(1) Except as provided in Sentence (2) and except at the leading edge at the top of a flight, every surface to which access is provided, including but not limited to flights of steps and ramps, exterior landings, porches, balconies, mezzanines, galleries and raised walkways, shall be protected by a guard on each side…). See guard height.
  • Open risers. Allowed in stairs serving a single dwelling unit or a house with a secondary suite, but not in most other stairs (9.8.4.9.OBC Div. B 9.8.4.9. Open Risers(1) Except as provided in Sentence (2), stairs shall have no open risers. (2) Open risers are permitted in (a) interior and exterior stairs that serve a single dwelling unit or a house with a secondary suite, (b) fire escape stairs, (c) stairs that are principally used for maintenance, (d) stairs that serve service…).

Common mistakes

  1. Using older numbers for run. If your reference was written for the 2012 code, compare its private stair run with the 2024 table before you frame.
  2. Uneven first or last riser after flooring is installed. Plan finished floor thicknesses so the 5 mm and 10 mm tolerances still work.
  3. Measuring headroom from the back of the tread rather than from the nosing line.
  4. A bulkhead or duct dropping below 1,950 mm partway down a basement stair.
  5. A door swinging over the stair with no landing.
  6. Winders that turn more than 45 degrees per tread or that are not consistent.

How to look it up yourself

In the 2024 Compendium, open Division B, Part 9, Section 9.8, "Stairs, Ramps, Handrails and Guards". Search for:

  • "Private stairs" (finds the table notes that define them)
  • "Dimensions for Risers" and "Dimensions for Rectangular Treads"
  • "Height Over Stairs"
  • "Required Landings"
  • "Winders"

For exam speed, learn that 9.8.2. is width and headroom, 9.8.4. is rise, run and tread shape, 9.8.6. is landings, 9.8.7. is handrails and 9.8.8. is guards.

Stairs, handrails and guards (Section 9.8) have their own section in both the House and Small Buildings exam syllabi. Read the free study guide for the House exam or Small Buildings exam, then try the free practice quiz on the exam page.

Based on the official 2024 Building Code Compendium on ontario.ca.

© King's Printer for Ontario, 2024. Reproduced with permission.

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Frequently asked questions

What is the maximum stair rise in Ontario?
For private stairs (inside a house or serving one house), the rise is 125 mm minimum and 200 mm maximum. Public stairs have a 180 mm maximum (Division B, Table 9.8.4.1.).
What is the minimum stair run in Ontario?
For private stairs the run of rectangular treads is 255 mm minimum and 355 mm maximum. Public stairs need at least 280 mm (Division B, Table 9.8.4.1.). If you learned the rules from material written for the 2012 code, check this value again.
What is the minimum headroom over stairs in a house?
1,950 mm for stairs serving a single dwelling unit or a house with a secondary suite, measured from a line tangent to the nosings. Other stairs need 2,050 mm, and stairs under beams and ducting in a secondary suite can drop to 1,850 mm (Division B, Article 9.8.2.2.).
How wide must stairs be in a house?
At least one stair between each floor level in a dwelling unit must be at least 860 mm wide (Division B, Sentence 9.8.2.1.(4)).
How much can risers vary?
Not more than 5 mm between adjacent risers and 10 mm between the tallest and shortest riser in a flight. Runs have the same tolerances (Division B, Article 9.8.4.4.).
Are open risers allowed?
Yes, for interior and exterior stairs serving a single dwelling unit or a house with a secondary suite, and a few other cases. They are not allowed in most other stairs (Division B, Article 9.8.4.9.).