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Code guide

Deck Railing Height in Ontario

Deck railing height in Ontario: 900 mm up to 1,800 mm above grade, 1,070 mm above that (2024 Code), plus baluster spacing, deck stairs and SB-7.
house deck up to 1,800 mm above ground
900 mm
house deck up to 1,800 mm above ground
house deck over 1,800 mm above ground
1,070 mm
house deck over 1,800 mm above ground
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

A deck serving one house in Ontario needs a guard (railing) at least 900 mm high if the deck surface is not more than 1,800 mm above finished ground, and at least 1,070 mm if it is higher (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…). The guard is required once the drop is more than 600 mm within 1.2 m of the deck 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…).

That is the short answer for homeowners, contractors and exam candidates. The rest of this page explains the details that trip people up: where to measure, baluster gaps, climbable designs, deck stairs and how SB-7 fits in. Confirm with your building department, since permits and local bylaws can add conditions.

Deck railing values at a glance

Deck situation Guard needed? Minimum height
Drop of 600 mm or less within 1.2 m Not required by 9.8.8.1. n/a
House deck, surface over 600 mm and up to 1,800 mm above finished ground Yes 900 mm
House deck, surface more than 1,800 mm above finished ground Yes 1,070 mm
Deck serving two or more dwelling units (not a house with a secondary suite) Yes, where the drop exceeds 600 mm 1,070 mm
Exterior stairs or landings more than 10 m above ground Yes 1,500 mm
Baluster spacing must stop a 100 mm sphere

"House" here means one dwelling unit, or a house with a secondary suite, which the code treats the same way for exterior guards (9.8.8.3.(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…).

Step 1: does the deck need a guard?

Under 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…, a guard is needed on every open side where the difference in elevation between the walking surface and the adjacent surface within 1.2 m is more than 600 mm. Decks, porches, exterior landings, balconies and flights of steps are all covered.

Two practical points:

  • Measure to the low point within 1.2 m. On a sloping yard, a deck that is 500 mm above grade at its edge can still need a guard if the ground drops further within 1.2 m.
  • Planters, benches and built-in seating near the edge change the effective walking surface. If someone can stand on them, ask your inspector how the drop will be measured.

Step 2: 900 mm or 1,070 mm?

The default height for every guard is 1,070 mm (9.8.8.3.(1)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 house deck gets a lower 900 mm minimum only while the walking surface is not more than 1,800 mm above finished ground (9.8.8.3.(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…). Above that, the deck goes back to 1,070 mm.

In practice, most ground-level and low decks can use 900 mm, while most decks off a main floor over a walk-out basement, and nearly all second-storey decks, need 1,070 mm. Measure your own grade: these are typical cases, not rules.

Step 3: openings, climbing and glass

  • Balusters and infill. Openings 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…). Check the gap under the bottom rail too.
  • Deck stairs. The triangle formed by the riser, the tread and the bottom rail of the stair 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. No member, attachment or opening between 140 mm and 900 mm above the deck may make the guard easy to climb, unless it can be shown not to be 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…). Horizontal rails or cables in that zone are the usual concern.
  • Glass panels. Must be laminated or tempered safety glass, or wired glass (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.").

Step 4: strength and SB-7

Guards must resist the loads set out in Table 9.8.8.2, referenced by 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…. For exterior guards serving not more than two dwelling units, the top of the guard must resist either a distributed load of 0.5 kN/m or a 1.0 kN concentrated load, whichever governs (Table 9.8.8.2.OBC Div. B Table 9.8.8.2. Minimum Specified LoadsTable 9.8.8.2. — Minimum Specified Loads Forming Part of Sentence 9.8.8.2.(1) Location of Guard | Horizontal Load Applied Inward or Outward at any Point at the Minimum Required Height of the Guard | Horizontal Load Applied Outward on Elements Within the Guard, Including Solid Panels and Balusters | Evenly Distributed…).

Most homeowners and deck builders never calculate this. Instead, they follow MMAH Supplementary Standard SB-7, "Guards for Housing and Small Buildings." A guard built to SB-7 is deemed to satisfy the load 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…). SB-7 groups wood guards into post and rail systems and cantilevered picket systems (SB-7 1.2.2.OBC SB-7 1.2.2. Classification (See Appendix A.)(1) The structural systems of guards described in this Supplementary Standard are grouped into the following classifications: (a) Post and Rail Systems, and (b) Cantilevered Picket Systems.). Exterior guards must follow Section 2 of SB-7 (SB-7 1.1.1.OBC SB-7 1.1.1. Scope (See Appendix A.)(1) This Supplementary Standard includes details for the construction of wood guards. (2) Guards located on the exterior of a building, where they may be subject to deterioration, shall be constructed in accordance with Section 2 of this Supplementary Standard. (See Appendix A.) (3) Guards located inside a building…), which calls for decay-resistant, preservative-treated or pressure-treated lumber, with treated cut ends (SB-7 2.1.5.OBC SB-7 2.1.5. Decay-Resistant Lumber (See Appendix A.)(1) Lumber for guard systems and floor systems shall be (a) a species resistant to decay, (b) preservative treated to prevent decay, or (c) pressure-treated. (2) All cut ends of preservative treated lumber shall be treated to prevent decay.). The connection details (post to rim joist, rail to post and so on) are drawn in SB-7's details and tables, so look them up rather than guessing fastener counts.

Deck stairs and handrails

Guards and handrails are different requirements. Exterior stairs serving one house do not need a handrail if they have not more than 3 risers, and need only one handrail once they have more than 3 (9.8.7.1.(3) and (4)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…). Required handrails are 865 mm to 1,070 mm high (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)…). On the stair, guard height is measured from a line through the 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…). See handrail height in Ontario for the details.

Common mistakes

  1. Assuming every house deck can use 900 mm. The 1,800 mm limit catches decks over walk-out basements.
  2. Measuring the drop only at the edge and ignoring sloping ground within 1.2 m.
  3. Cable or horizontal rail infill in the 140 mm to 900 mm zone without checking 9.8.8.6.
  4. Gaps under the bottom rail larger than 100 mm.
  5. Copying fastener details from memory instead of SB-7.
  6. Building first, permitting later. A guard that passes the code can still fail a municipal inspection if the permit drawings showed something else.

How to look it up yourself

In the 2024 Compendium, open Division B, Part 9, Section 9.8 and go to Subsection 9.8.8. Search for these phrases from the code text:

  • "Height of Guards"
  • "1,800 mm above the finished ground level"
  • "spherical object having a diameter of 100 mm"
  • "facilitate climbing"
  • "Guards for Housing and Small Buildings" (to jump to the SB-7 reference)

SB-7 itself is in Volume 2 of the Compendium with the other Supplementary Standards.

Guards (Section 9.8) are on the House exam syllabus. Read the free House exam study guide and try the free practice quiz on that page to see how these rules are tested.

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

How high does a deck railing have to be in Ontario?
For a deck serving one house, the guard must be at least 900 mm high where the deck surface is not more than 1,800 mm above finished ground, and at least 1,070 mm where it is higher (Division B, Article 9.8.8.3.). Decks serving more than one dwelling unit, other than a house with a secondary suite, need 1,070 mm.
At what height does a deck need a railing?
When the deck surface is more than 600 mm above the adjacent ground within 1.2 m of the edge (Division B, Sentence 9.8.8.1.(1)). Measure the drop to the lowest point within that 1.2 m.
Do deck stairs need a railing?
A guard is needed on any side of the stairs with a drop of more than 600 mm. Separately, exterior stairs serving one house need one handrail once they have more than 3 risers (Division B, Article 9.8.7.1.).
What is the maximum gap between deck balusters?
Openings in a required guard must prevent a 100 mm sphere from passing through (Division B, Sentence 9.8.8.5.(1)).
Is there a standard way to build a wood deck guard?
Yes. MMAH Supplementary Standard SB-7, Guards for Housing and Small Buildings, gives post and rail and cantilevered picket details. Guards built to SB-7 are deemed to meet the load requirements (Division B, Sentence 9.8.8.2.(6)).