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Code guide

Ontario Building Code Guard Height (Railings, Decks and Stairs)

Railing (guard) height in Ontario: 1,070 mm by default, 900 mm inside a house and on decks up to 1,800 mm. Plus baluster gaps and climbing rules.
minimum guard height, the general rule
1,070 mm
minimum guard height, the general rule
inside a house, or a deck up to 1,800 mm
900 mm
inside a house, or a deck up to 1,800 mm
drop beyond which a guard is required
600 mm
drop beyond which a guard is required
sphere that guard openings must stop
100 mm
sphere that guard openings must stop

Last updated

Under the 2024 Ontario Building Code, a guard (the code's word for a protective railing) must be at least 1,070 mm high, except that guards inside a house, and exterior guards serving a single house where the walking surface is not more than 1,800 mm above finished ground, can be 900 mm (OBC Div. B 9.8.8.3.OBC Div. B 9.8.8.3. Height of Guards(1) Except as provided in Sentences (2) to (3.1), all guards shall be not less than 1,070 mm high. (2) All guards within dwelling units or within houses with a secondary suite including their common spaces shall be not less than 900 mm high. (3) Exterior guards serving not more than one dwelling unit or a house with a…). A guard is needed wherever a walking surface has a drop of more than 600 mm within 1.2 m of its edge (OBC Div. B 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…).

This page covers houses and small buildings under Part 9 of Division B. Your municipality's building department has the final say on your project, and local bylaws or permit conditions can add requirements.

Key guard values at a glance

Situation Minimum guard height Where to look
General rule (any guard not covered below) 1,070 mm 9.8.8.3.(1)
Inside a dwelling unit, or inside a house with a secondary suite 900 mm 9.8.8.3.(2)
Exterior guard serving one dwelling unit (or a house with a secondary suite), surface 1,800 mm or less above finished ground 900 mm 9.8.8.3.(3)
Same exterior guard, surface more than 1,800 mm above finished ground 1,070 mm 9.8.8.3.(1)
Exterior stairs and landings more than 10 m above adjacent ground 1,500 mm 9.8.8.3.(3.1)
Drop that triggers a guard more than 600 mm within 1.2 m 9.8.8.1.(1)
Openings through a required guard must stop a 100 mm sphere 9.8.8.5.(1)
Triangle at riser, tread and bottom rail must stop a 150 mm sphere 9.8.8.5.(2)
No-climb zone 140 mm to 900 mm above the walking surface 9.8.8.6.(1)

These are our own summary of the articles, not a copy of the code. Read the full sentences before you build or answer an exam question.

When a guard is required

The trigger is a difference in elevation of more than 600 mm between the walking surface and the adjacent surface within 1.2 m (9.8.8.1.(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…). The code lists the kinds of places this covers: flights of steps, ramps, exterior landings, porches, balconies, mezzanines, galleries and raised walkways. Any side not protected by a wall needs a guard. The leading edge at the top of a flight is excluded, since that is where you step onto the stair.

Note the 1.2 m part. If the ground slopes away so that the drop exceeds 600 mm a short distance from the edge, the guard can still be required even though the drop right at the edge is less.

A few places are exempt: loading docks, floor pits in repair garages, and areas reached only for maintenance (9.8.8.1.(2)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…).

How high: 900 mm or 1,070 mm

Start from 1,070 mm and then check whether an exception lets you use 900 mm (9.8.8.3.OBC Div. B 9.8.8.3. Height of Guards(1) Except as provided in Sentences (2) to (3.1), all guards shall be not less than 1,070 mm high. (2) All guards within dwelling units or within houses with a secondary suite including their common spaces shall be not less than 900 mm high. (3) Exterior guards serving not more than one dwelling unit or a house with a…):

  • Inside a house. All guards within a dwelling unit, or within a house with a secondary suite including its common spaces, can be 900 mm. That covers an open stairwell, a loft edge or a basement stair guard.
  • Low exterior decks and porches of a house. An exterior guard serving not more than one dwelling unit (or one house with a secondary suite) can be 900 mm, but only where the walking surface is not more than 1,800 mm above finished ground.
  • Everything else needs 1,070 mm, including a house deck more than 1,800 mm above grade and guards in common areas of apartment buildings.
  • Very high exterior stairs and landings, more than 10 m above the adjacent ground, need 1,500 mm.

On a flight of stairs, height is measured vertically from the top of the guard to a line drawn through the tread nosings (9.8.8.3.(4)OBC Div. B 9.8.8.3. Height of Guards(1) Except as provided in Sentences (2) to (3.1), all guards shall be not less than 1,070 mm high. (2) All guards within dwelling units or within houses with a secondary suite including their common spaces shall be not less than 900 mm high. (3) Exterior guards serving not more than one dwelling unit or a house with a…).

Openings and climbing

Height alone does not make a compliant guard.

  • Openings. Openings through a required guard must stop a 100 mm sphere (9.8.8.5.(1)OBC Div. B 9.8.8.5. Openings in Guards(1) Except as permitted in Sentences (3) and (4), openings through guards shall be of a size that prevents the passage of a spherical object having a diameter of 100 mm. (See Note A-9.8.8.5.(1) and (3)) (2) Except for guards that serve industrial occupancies, the triangular openings formed by stair risers, stair…). On stairs, the triangle formed by the riser, the tread and the bottom element of the guard must stop a 150 mm sphere (9.8.8.5.(2)OBC Div. B 9.8.8.5. Openings in Guards(1) Except as permitted in Sentences (3) and (4), openings through guards shall be of a size that prevents the passage of a spherical object having a diameter of 100 mm. (See Note A-9.8.8.5.(1) and (3)) (2) Except for guards that serve industrial occupancies, the triangular openings formed by stair risers, stair…).
  • Climbing. Required guards, outside industrial occupancies, must be designed so that nothing between 140 mm and 900 mm above the floor helps a child climb, unless it can be shown the openings are not a hazard (9.8.8.6.OBC Div. B 9.8.8.6. Guards Designed Not to Facilitate Climbing(1) Guards required by Article 9.8.8.1., except those in industrial occupancies and where it can be shown that the location and size of openings do not represent a hazard, shall be designed so that no member, attachment or opening located between 140 mm and 900 mm above the floor or walking surface protected by the…).
  • Strength. Guards must resist the loads in Table 9.8.8.2 (9.8.8.2.OBC Div. B 9.8.8.2. Loads on Guards(1) Except as provided in Sentences (2), (3), (5) and (6), guards shall be designed to resist the specified loads prescribed in Table 9.8.8.2. (2) The size of the opening between any two adjacent vertical elements within a guard shall not exceed the limits required by Sentence 9.8.8.5.(1) when each of these elements…). Wood guards built to MMAH Supplementary Standard SB-7, "Guards for Housing and Small Buildings," are deemed to meet that requirement (9.8.8.2.(6)OBC Div. B 9.8.8.2. Loads on Guards(1) Except as provided in Sentences (2), (3), (5) and (6), guards shall be designed to resist the specified loads prescribed in Table 9.8.8.2. (2) The size of the opening between any two adjacent vertical elements within a guard shall not exceed the limits required by Sentence 9.8.8.5.(1) when each of these elements…).
  • Glass. Glass in a guard must be laminated or tempered safety glass, or wired glass, to the listed CSA/CGSB standards (9.8.8.7.OBC Div. B 9.8.8.7. Glass in Guards(1) Glass in guards shall be (a) safety glass of the laminated or tempered type conforming to CAN/CGSB-12.1, "Safety Glazing," or (b) wired glass conforming to CAN/CGSB-12.11-M, "Wired Safety Glass.").

Windows and doors count too

Guards are not only for decks and stairs. In residential buildings, an openable window must have a guard or an opening limiter (releasable only with tools or special knowledge) that keeps the opening to 100 mm, unless the bottom of the openable part is more than 900 mm above the floor or less than 1,800 mm above the ground outside (9.8.8.1.(4) and (5)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…). A door where the floor is more than 600 mm above the surface on the other side, such as a "Juliet" door, needs a guard or a similar limiting mechanism (9.8.8.1.(3)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…).

Common mistakes

  1. Using 900 mm on a high deck. The 900 mm exception for exterior guards stops at 1,800 mm above finished ground. A second-storey deck usually needs 1,070 mm.
  2. Measuring a stair guard from the back of the tread. The code measures from the nosing line.
  3. Ignoring the 1.2 m distance. Check the grade within 1.2 m of the edge, not just directly below it.
  4. Horizontal "ladder" infill between 140 mm and 900 mm. It invites a climbing question even when the height is right.
  5. Gaps at the bottom of stair guards. The 150 mm triangle rule is easy to miss when the bottom rail follows the stringer.
  6. Forgetting low windows on upper floors and walk-out doors with no deck yet.

How to look it up yourself

Open the 2024 Building Code Compendium (Volume 1 for Division B) and go to Part 9, Section 9.8, "Stairs, Ramps, Handrails and Guards". Subsection 9.8.8. holds every guard rule. Useful search terms that appear in the code text:

  • "Height of Guards" (the heading of 9.8.8.3.)
  • "difference in elevation" (the trigger in 9.8.8.1.)
  • "spherical object" (opening sizes in 9.8.8.5.)
  • "facilitate climbing" (9.8.8.6.)
  • "Guards for Housing and Small Buildings" (the SB-7 reference)

In the exam, search the heading first, then read every sentence of the article. Guard questions often hinge on the exceptions in Sentences (2), (3) and (3.1).

Guard rules are core material for the House and Small Buildings exams. Read the free study guide for the House exam or Small Buildings exam and test yourself with the free practice quiz on each 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 minimum railing height in Ontario?
Under the 2024 Ontario Building Code, a guard must be at least 1,070 mm high unless an exception applies. Guards inside a dwelling unit, and exterior guards serving one house where the walking surface is not more than 1,800 mm above finished ground, can be 900 mm (Division B, Article 9.8.8.3.).
When is a guard required?
Where a walking surface, such as a deck, porch, landing or flight of stairs, has a drop of more than 600 mm to an adjacent surface within 1.2 m, and the side is not protected by a wall (Division B, Article 9.8.8.1.).
How is guard height measured on stairs?
Vertically from the top of the guard to a line drawn through the tread nosings, not from the back of the tread (Division B, Sentence 9.8.8.3.(4)).
How far apart can balusters be?
Openings in a required guard must stop a 100 mm sphere from passing through. On stairs, the triangle formed by the riser, tread and bottom rail must stop a 150 mm sphere (Division B, Article 9.8.8.5.).
Can I use horizontal rails on a deck guard?
Required guards must not have members, attachments or openings between 140 mm and 900 mm above the walking surface that make the guard easy to climb, unless it can be shown the location and size of the openings are not a hazard (Division B, Article 9.8.8.6.). Horizontal rails in that zone usually raise this question, so check with your building department.