Deck Railings in Ontario, and What the Code Requires

Railing is where a deck passes or fails its inspection, and where most of the bad advice online sits. Two of the numbers people quote confidently were changed in 2022, and one of the most repeated claims about glass railings is about a completely different kind of building.

Here is what the Ontario Building Code actually requires on a house deck.

Part 9 of the Building Code, which is the part that governs houses. Checked September 2026. Your plans examiner is the final word.

When you need a guard at all

A guard is required once the deck sits more than 600 mm above the surface within 1.2 m of it. Note the wording: more than 600 mm, not 600 mm or more. 600 mm is 23.6 inches, so a deck at 24 inches is over the line either way.

That 600 mm figure turns up three separate times in Ontario deck rules and means something different each time. It is the single most common mix-up in this subject:

• More than 600 mm to the walking surface means you need a guard.
• Not more than 600 mm to the underside of the joists is one of five conditions for skipping frost-depth footings.
• 600 mm also appears in most municipal permit thresholds, usually paired with a 10 m² area limit.

The guard rule measures to the deck surface. The footing exemption measures to the bottom of the joists. On a deck framed in 2x8s that is most of a foot apart, and it decides which rule you are under. Our footing depth guide covers the other two.

36 inches or 42

Both, depending on how high the deck is.

Up to 1.8 m (5 ft 11 in) above grade, a guard on a house deck is 900 mm (36 in). Above 1.8 m it goes to 1070 mm (42 in). That odd 5 ft 11 in figure is just 1.8 m in imperial, which is why it shows up on municipal drawings looking so arbitrary.

The practical trap is a sloping yard. A deck that is 5 ft 6 in off the ground at the house and 6 ft 3 in at the far corner crosses the line partway along, and the guard height is set by the worst case, not the average.

The gap rules

A guard has to stop a 100 mm sphere anywhere through it. That is the four inch rule, and it is not a residential concession, it is the general rule for almost every building.

One exception works in your favour. The triangle formed by the riser, the tread and the bottom rail at the base of a stair guard only has to stop a 150 mm sphere. Without that allowance, stair guards would be very difficult to build.

Nothing climbable, and the myth about it

Between 140 mm and 900 mm above the deck, no part of a required guard may help a child climb it. This is a requirement, not a recommendation, and it is what rules out horizontal rails on the outside face.

You will read online that Ontario dropped or relaxed this rule. It did not. Two things feed that belief and both are wrong:

• Something at 140 mm did change on 1 January 2022, but it was the minimum curb height in a garage, which went from 150 mm to 140 mm. Different article, nothing to do with climbing.
• Most of the writing about climbability being relaxed is from British Columbia, where it has been fought through appeal rulings. BC is a different code. It does not apply here.

If a supplier tells you a horizontal railing is fine in Ontario, ask which article says so.

Two numbers that changed in 2022

These catch out people working from older material, including some municipal drawings still in circulation.

• Handrail height is 865 mm to 1070 mm. The maximum used to be 965 mm. Any source still saying 865 to 965 is out of date.
• Minimum stair run is 255 mm (about 10 in). It used to be 210 mm, about 8¼ in. That is a 45 mm jump, and it changes how far a flight of stairs projects into a yard, which can matter on a tight lot.

The handrail itself has to be continuously graspable from the bottom riser to the top, with nothing on or above it breaking your grip, and at least 50 mm of clearance behind it, or 60 mm if the surface behind is rough.

Part 9 sets no diameter for a handrail. If you see a specific thickness quoted as an Ontario requirement for a house deck, it has been lifted from Part 3, which covers large buildings.

Cable railings have a new problem

The 2024 Code added a sentence that did not exist before. The spacing between vertical guard elements now has to still pass the 100 mm sphere test while being pushed apart with a 0.1 kN load, which is about 22 lb.

That is aimed squarely at flexible infill. Cable, wire rope and thin pickets can sit at code spacing while nobody is touching them and spread well past it under a shoulder. If you are considering a cable railing, that is the question to put to the supplier in writing.

Glass railings: tempered is allowed on a house deck

This is the one we get asked about most, and the common answer is wrong.

On a house deck, the Code requires safety glass of the laminated or tempered type. Tempered is expressly permitted. There is no requirement to use laminated glass.

The reason people believe otherwise is real, but it is about a different kind of building. After glass balcony panels failed in downtown Toronto, Ontario brought in a supplementary standard with much stricter rules, including heat-strengthened laminated glass near a floor edge. That standard is referenced from Part 3, which governs apartment and condo buildings. A backyard deck on a house is a Part 9 building and is not covered by it.

None of which makes tempered the right choice automatically. Laminated holds together in the frame if it ever breaks and tempered does not, which is exactly why the rules for eleventh-floor balconies are stricter. On a deck two feet off the ground that matters a good deal less.

Anything not made of wood needs an engineer

Several municipalities are explicit about this, and it surprises people who assumed a manufactured railing kit is automatically approved:

• Oakville and Milton both require an engineered stamped detail for any guard system with a non-wood component, or any guard built higher than 3 ft 6 in.
• Oshawa requires stamped details from a licensed Ontario engineer for any prefabricated guard or railing system.

In practice the manufacturer supplies that documentation for aluminum and glass systems. It is worth confirming it exists before the order goes in, because a permit can stall on it.

Check the drawing, not just the article number

Municipal deck drawings are genuinely useful and we work from them. They also carry mistakes. Halton Hills cites article 9.8.8.3 for its handrail requirement, but 9.8.8.3 is the height of guards, and handrails live in 9.8.7. Clarington publishes a standard detail drawn in 2007, so its stair run predates the 2022 change.

Use them for what the town expects to see. Confirm the numbers against the Code.

What we build to

• Guards at 42 in wherever the deck is near the 1.8 m line, rather than measuring to the inch and hoping
• Pickets set so a 4 in sphere will not pass, measured after the wood has dried and shrunk
• Nothing horizontal on the outside face between 140 mm and 900 mm
• Handrails that are actually graspable, not a 2x4 on edge
• Rise and run set out for the whole flight at once so no two steps differ by more than 5 mm
• Engineered details in hand before a non-wood railing is ordered

Most of this is decided before anything is cut. A railing that is 2 inches short is not adjusted, it is rebuilt, and the same is true of a flight of stairs with one riser out of step. See our railings and deck stairs pages for what we build.

Sources: 2024 Ontario Building Code, Ontario: changes to stairs, guards and handrails, Markham Builder Tip 64, Markham Builder Tip 88, Markham Builder Tip 54, Halton Hills deck guide, Oakville deck drawings, Milton deck drawings, Oshawa deck guide.