How High Does a Deck Railing Need to Be in BC? Guard Rules, Explained

When a railing is required at all

The code calls a railing a guard, and it requires one on any open side of a walking surface — decks, porches, landings, stairs — where there is a difference in elevation of more than 600 mm between the walking surface and the adjacent surface (BCBC 9.8.8.1). That 600 mm line is the same threshold that triggers most deck permits in Metro Vancouver, which is not a coincidence: it's the height at which a fall starts to hurt.

Below 600 mm you can choose to go without, or build a decorative railing. One catch people miss: a guard that isn't required still has an openings rule — it must either block a 100 mm sphere or allow a 200 mm one to pass, so that a child can't get a head stuck (9.8.8.5).

How high: 900 mm or 1,070 mm

The default guard height is 1,070 mm (about 42 inches). The residential exception most homeowners qualify for is 900 mm (about 36 inches) — and it applies to an exterior guard serving not more than one dwelling unit, where the walking surface is not more than 1,800 mm above finished ground (9.8.8.3). In practice:

• A backyard deck on a single-family home, less than 1.8 m off the ground → 900 mm minimum.
• The same deck higher than 1.8 m (a second-storey deck, a deck over a walkout basement) → 1,070 mm.
• Balconies and decks on strata and multi-unit buildings, and anything commercial → 1,070 mm.
• Guards on the open side of a flight of stairs → 900 mm, measured vertically from a line through the tread nosings.

Taller is always permitted. Many homeowners choose 1,070 mm on a 900 mm deck for the simple reason that a 36-inch rail sits below the hip of most adults.

The 100 mm sphere

Openings through a required guard must be small enough that a 100 mm sphere cannot pass (9.8.8.5). That governs picket spacing (about 95 mm clear is the usual target), the gap between the deck surface and the bottom rail, the gap between glass panels and posts, and cable spacing — which is why cable systems specify tension so carefully.

The climbing rule, and what changed

For years the code also said a guard could not contain anything between 140 mm and 900 mm above the deck that would help a child climb it — which effectively ruled out horizontal cables and rails. The BC Building Code narrowed that rule so it now applies only to guards protecting a level more than 4.2 m above the adjacent level (9.8.8.6). For almost every house deck in Metro Vancouver, horizontal designs are therefore code-compliant — outside the City of Vancouver, which kept the older, stricter wording in its own by-law until it harmonized with the national code on September 15, 2025. Since then, horizontal cable and rod guards are an option in Vancouver too for decks under that 4.2 m line.

Two cautions: a horizontal system still has to meet the 100 mm sphere test under load (cables sag and stretch), and some inspectors ask for the manufacturer's engineering. Use a system designed as a guard, not hardware-store cable.

Glass guards

Glass in a guard must be laminated or tempered safety glass conforming to CAN/CGSB-12.1 (9.8.8.7) — never ordinary float glass. The City of Vancouver's by-law goes a step further and requires glass guards to carry a top rail capable of transferring the guard loads to the neighbouring panels or the structure if a panel fails, which is why fully frameless, topless glass is restricted there. Elsewhere in Metro Vancouver, frameless systems are generally assessed on the manufacturer's engineering. On balconies and sundecks over living space, the posts also have to be detailed through the waterproofing correctly — a railing post is the most common place a vinyl membrane is punctured.

Loads, posts and why "sturdy" isn't a feeling

Guards must resist specified loads — a horizontal push on the top rail, a concentrated point load, and loads on the infill (Table 9.8.8.2). What actually delivers that is the post connection: blocking in the frame, through-bolts rather than lag screws into a single rim joist, and post bases that aren't sitting in rot. A railing that moves when leaned on has failed this test regardless of how it was built.

Stairs and handrails, briefly

Private exterior stairs (those serving a single dwelling) need a rise between 125 and 200 mm and a run between 255 and 355 mm, consistent through the flight (9.8.4.1 and 9.8.4.2). A handrail is required on exterior stairs with more than three risers; one side is enough when the stair serves a single dwelling, and the handrail has to sit 865–1,070 mm above the tread nosings (9.8.7.1 and 9.8.7.4). On most deck stairs the guard's top rail and the handrail are the same element, so its height has to satisfy both rules at once.

Where we come in

We design and build railings and stairs for new decks and retrofit them on existing ones across Metro Vancouver — aluminum picket, glass, cable and wood — to the code that applies in your municipality, and we handle the permit drawings when one is needed. If you're unsure which height applies to your deck, the answer is usually in how far it sits above the ground; a free site assessment settles it in minutes.

Quick answers

How high does a deck railing have to be in BC? 900 mm (36") for an exterior guard on a single-family home where the deck is no more than 1.8 m above finished ground; 1,070 mm (42") above that height and on multi-unit and commercial buildings.

Do I need a railing on a low deck? Not if the drop is 600 mm or less — but if you build one, its openings must block a 100 mm sphere or pass a 200 mm one.

Are horizontal cable railings legal in BC? Yes for guards protecting a level 4.2 m or less above the adjacent level, and as of September 15, 2025 that includes the City of Vancouver. Use an engineered system and keep the openings under 100 mm under load.