How far apart can balusters be in an Ottawa home?

Baluster spacing inside a dwelling unit is set by the guard opening rule in the 2024 Ontario Building Code: no opening may allow a 100 mm (about 4 in.) sphere to pass through. That is the rule that governs baluster spacing on an interior stair or landing guard.

The triangle formed between a stair tread, a riser and the underside of a guard has its own limit: no opening there may allow a 150 mm sphere to pass through.

A few other guard rules apply at the same time. The guard itself must be at least 900 mm (about 35 1/2 in.) high, measured from the floor or from a line tangent to the stair nosings. Nothing between 140 mm and 900 mm above the floor or tread may form a pattern or shape that makes the guard climbable, unless it can be shown not to be a hazard. These rules work together, so baluster spacing, height and pattern all need to be considered as a set.

What this means in practice is that the carpenter measures the actual gap between each baluster, not the baluster centre-to-centre distance, and that gap must stay under 100 mm everywhere. The shape and profile of the baluster affects how the sphere test works, so a carpenter should confirm the spacing with the specific baluster profile in hand before installation.

A few things worth asking the carpenter before work starts:

• Whether the existing guard post and top rail can carry the new balusters, or whether the structure needs reinforcement
• What material the balusters will be, and how they will be fastened at the top and bottom rail
• Whether the guard height meets the 900 mm minimum at every point, including at the bottom of a raked section over the stair

Make sure you have a written contract that sets out the scope, the baluster material and spacing, the price, and any warranty before the carpenter begins.