What's the right gap for child safety on my Vancouver deck railing?

BC Building Code requires that deck railing openings cannot allow passage of a 100mm (4-inch) sphere — this is the critical child safety standard for all Metro Vancouver deck railings on any deck more than 600mm (approximately 2 feet) above grade.

This 100mm rule applies to all openings in the railing system — between balusters (spindles), between horizontal rails, and between the bottom rail and the deck surface. The measurement is taken at the largest opening, so if your balusters are spaced to create a 3.5-inch gap at the top but the gap widens to 4.5 inches at the bottom due to angled cuts or settling, the railing fails code. Building inspectors use an actual 100mm sphere (about the size of a large orange) to test compliance during final inspection.

Railing height must be minimum 42 inches (1,070mm) from the deck surface to the top of the railing. This height requirement works in conjunction with the 100mm spacing rule — both are designed to prevent children from climbing over or slipping through railings. The combination of adequate height and proper spacing creates an effective safety barrier.

Common railing configurations that meet BC code include traditional wood balusters spaced 3.5 inches on center, aluminum picket railings with 4-inch maximum spacing, cable railings with horizontal cables spaced no more than 4 inches apart, and glass panel railings (which eliminate gaps entirely). Many homeowners choose glass panels specifically because they provide unobstructed views while exceeding safety requirements, though glass railings cost significantly more — typically $150-$350 per linear foot versus $50-$150 for standard picket railings.

Metro Vancouver's marine climate affects railing material choices for child safety. Wood balusters can shrink and create wider gaps as they dry, especially in the first year after installation. Pressure-treated balusters may twist or bow, potentially creating code violations. Aluminum and composite railing systems maintain consistent spacing regardless of weather conditions. If you're building with wood railings, specify kiln-dried lumber and plan for a follow-up inspection after the first winter to check for gap widening.

Strata properties often have additional requirements beyond BC Building Code minimums. Many strata corporations specify railing styles, colours, and materials in their bylaws to maintain architectural consistency. Some require glass railings or prohibit certain baluster styles. Always check your strata's alteration guidelines before replacing or modifying deck railings — you'll need written approval before starting work.

Professional installation is essential for code compliance. Railing systems must be properly anchored to resist the required loads (200 lbs concentrated force at any point along the top rail), and spacing must be precisely maintained across the entire railing run. DIY railing installation often results in code violations during inspection, requiring costly corrections. Building inspectors in Metro Vancouver municipalities are particularly thorough about child safety spacing — it's one of the most commonly cited violations on deck permits.

Need help finding a deck contractor who understands BC Building Code requirements? Vancouver Deck Contractors can match you with experienced professionals who ensure your railing meets all safety standards.