What is the NB building code requirement for deck railing height in New Brunswick?

The New Brunswick Building Code requires a minimum railing (guard) height of 900mm (approximately 36 inches) measured from the deck surface to the top of the railing for residential decks. This requirement applies to any deck, balcony, or raised platform where the walking surface is 600mm (24 inches) or more above the adjacent grade or finished floor level below. The code is based on the National Building Code of Canada (NBCC), which New Brunswick adopts with provincial amendments, and this guard height requirement is one of the most fundamental safety provisions in the entire residential construction section.

The 900mm measurement is taken vertically from the top of the finished deck surface — meaning the top of the decking boards, not the top of the joists — to the highest point of the guard rail. If your deck has a composite cap rail or a wide flat rail on top, the measurement goes to the top of that cap. This distinction matters because some homeowners install a decorative flat board on top of their railing posts and assume the height is measured to the post top, not the cap — the code measures to whatever the highest continuous graspable or protective surface is.

It is important to understand the distinction between guards and handrails in the code, as these are two separate requirements that often overlap but serve different purposes. A guard is the protective barrier along the open edge of a deck to prevent people from falling off. A handrail is the graspable rail along a staircase that provides support while ascending or descending. On a deck staircase, you need both — the guard function prevents falls off the open side of the stairs, and the handrail provides something to grip.

For deck stairs specifically, the NB code requires a handrail on at least one side of any staircase. The handrail must be graspable, meaning it must have a circular or nearly circular cross-section between 32mm and 38mm in diameter so that a person can wrap their hand around it securely. A flat 2x6 board on top of stair posts does not meet the graspable handrail requirement — this is one of the most common code violations found during residential inspections in New Brunswick. You can mount a graspable handrail on top of or inside a broader railing system, but the graspable portion must fall within that 32-38mm diameter range.

The guard system must also meet structural requirements. Under the NB code, guards must be designed to resist a horizontal force of 0.5 kN per metre (roughly 34 pounds per linear foot) applied at the top of the guard. This means your railing posts must be securely fastened — typically with through-bolts or structural screws into the rim joist or deck frame, not simply nailed or toe-screwed. Post spacing generally should not exceed 6 feet on centre to maintain adequate rigidity.

Baluster and Infill Requirements

The openings in any guard system — whether between balusters, glass panels, or any other infill — must not permit the passage of a sphere 100mm (4 inches) in diameter at any point. This means the clear space between individual balusters cannot exceed 100mm. This provision is specifically designed to prevent small children from getting their heads caught between railing members. Additionally, the guard must not have any features in the lower 600mm that would facilitate climbing — meaning horizontal rails, decorative elements, or any configuration that could serve as a foothold or ladder for a child. This climbing restriction is why vertical balusters are the standard infill pattern for residential deck railings, and why some municipalities in New Brunswick look closely at horizontal cable railing systems, which can potentially be climbed by children.

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