Request a Free QuoteNiagara Region, Ontario · LANE: DECK RAILING HEIGHT GUIDE
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How high does a deck railing have to be in Ontario? The short answer is that there is no single number -- it depends on how high your deck sits, and getting this wrong is a real risk, since at least one local competitor currently publishes a single blanket figure that is wrong for one of the two cases. Here is the actual rule, at a glance. A guard (the Building Code's own term for what most homeowners call a railing) is required wherever a deck's walking surface sits more than 600 millimetres above the adjacent ground -- Ontario Building Code Part 9, Article 9.8.8.1. Below that, no guard is required at all. Once a guard is required, its minimum height depends on elevation: 900 millimetres where the walking surface is 1 800 millimetres (about 6 feet) or less above grade, and 1 070 millimetres where it sits higher than that -- Article 9.8.8.3. Two figures, not one, and the higher figure only kicks in once a deck clears roughly 6 feet of elevation. Openings through an ordinary guard must be small enough that a 100 millimetre sphere cannot pass through them -- Article 9.8.8.5. -- and at a stair guard specifically, the triangular openings formed by the risers, treads, and bottom rail have their own, stricter limit: a 150 millimetre sphere -- Article 9.8.8.5.(2). Separate from height and opening size, a no-climb rule applies to horizontal rail elements between 140 and 900 millimetres above the walking surface: the national Building Code text limits this rule to guards protecting a level more than 4.2 metres above grade, but Ontario's own amendments remove that height threshold entirely, so in Ontario the no-climb requirement applies to essentially every residential deck guard, not just a deck that happens to clear 4.2 metres -- independently corroborated by the City of St. Catharines' own Deck and Porch Guide, which states the identical no-threshold rule in its own words. All of these figures have carried over unchanged, at unchanged article numbers, through the January 1, 2025 Building Code edition and the current Ontario Amendments document (dated July 17, 2026, under O. Reg. 242/26) -- checked article by article. One honest limit: that amendment document is available from the Ministry by request only, not posted on e-Laws, so its own provenance here is Moderate -- the no-climb correction itself is graded Strong, independently corroborated by St. Catharines' own published guide, not resting on the amendment document alone. Confirm the current figures with your municipality's building department before you build; a Code edition can change, and this page states the figures as of 2026-08-20.
This page is a Code-figure reference for guard and railing height only; it does not cover material choice, pricing, or the inspection sequence. For pressure-treated versus composite decking material and real Niagara $/sq ft pricing, see /decking-material-guide/. For when and how a guard gets checked during your build (footing, framing, and final inspection), see /niagara-deck-inspection-guide/. For each Niagara municipality's permit process and thresholds, see /niagara-deck-permit-guide/.
It depends on how high your deck's walking surface sits above grade. Below 1 800 millimetres (about 6 feet) of elevation, a guard must be at least 900 millimetres high. Above that threshold, it must be at least 1 070 millimetres high. Two figures, not one blanket number -- Ontario Building Code Part 9, Article 9.8.8.3.
Only if the walking surface sits more than 600 millimetres above the adjacent ground (Article 9.8.8.1.). A low deck at or below that elevation does not require a guard at all under the Building Code.
An ordinary guard's openings must be small enough that a 100 millimetre sphere cannot pass through (Article 9.8.8.5.). At a stair guard specifically, the triangular openings formed by the risers, treads, and bottom rail have a stricter, separate limit: a 150 millimetre sphere (Article 9.8.8.5.(2)).
Yes. The national Building Code text limits the no-climb rule (no horizontal rail elements between 140 and 900 millimetres above the walking surface that a child could use as a ladder) to guards protecting a level more than 4.2 metres above grade. Ontario's own amendments remove that height threshold entirely, so in Ontario the no-climb requirement applies to essentially every residential deck guard -- independently corroborated by the City of St. Catharines' own Deck and Porch Guide, which publishes the identical no-threshold rule in its own words.
None -- a deck with its walking surface 600 millimetres (about 2 feet) or less above grade falls under the Article 9.8.8.1. trigger threshold itself, so no guard is required at all. Once a deck exceeds 600 millimetres, a guard is required and the 900 mm/1 070 mm split above applies.
A deck with its walking surface at or below 1 800 millimetres (roughly 6 feet) above grade needs a guard at least 900 millimetres high -- the lower of the two Article 9.8.8.3. figures. This is the elevation bracket most standard single-level Niagara decks fall into.
Once a deck's walking surface sits higher than 1 800 millimetres above grade -- a raised deck off a walkout basement or second storey, for example -- the guard must be at least 1 070 millimetres high, the higher of the two Article 9.8.8.3. figures.
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