BC Stair Code Requirements for Metal Stair Projects

Vancouver Stairs coordinates metal stair projects to BC Building Code requirements — guards, handrails, open risers, structural connections, and the engineering path all need early decisions before fabrication starts.

Code requirements affect nearly every custom metal stair project. Even when the stair is a design feature, it still has to be safe, usable, and reviewable by the people responsible for the building. Understanding which clauses apply — and where interpretation still lands with the authority having jurisdiction (AHJ) — is the foundation of a project that moves through permitting without delays.

This article is not a substitute for code review by the authority having jurisdiction, an architect, or an engineer. It is a fabrication-focused overview of the topics that tend to shape custom metal stair projects in British Columbia.

Guards: height, openings, and what drives the steel design

Guard height is the most commonly misread requirement on custom stair projects. BC Building Code 2018 Section 9.8.8.3 sets the minimums:

• 900 mm minimum guard height within a dwelling unit, and for exterior guards serving not more than one dwelling unit where the walking surface is not more than 1,800 mm above grade.
• 1,070 mm minimum guard height in most other situations — exterior guards at height, commercial, and multi-family common areas.

The guard height is measured from the walking surface — the finished floor, tread, or landing that people stand on — not from the subfloor or rough framing. In renovation projects where finished floor heights are uncertain during fabrication, this is a common source of guards that measure short on inspection. Resolve finished-floor heights before steel is ordered.

Opening limits in guards follow the 100 mm sphere rule from BCBC 9.8.8.5. Openings through the guard cannot pass a 100 mm sphere. For picket guards, this drives the maximum gap between vertical members. For cable guards, it requires that cable spacing be evaluated after realistic deflection under load — not just at rest — which is why cable guards need stamped drawings showing post spacing, cable diameter, and tensioning targets together.

Climbability is a separate question under BCBC 9.8.8.6. Horizontal members close together can be treated as a ladder by some AHJ interpretations, particularly near strata common areas, childcare spaces, or anywhere with elevated fall risk. Vertical pickets and cable systems handle this differently and the project drawings should address it explicitly.

Handrails: graspability, height, and extensions

Handrails serve a different function from guards — they are the element a person holds onto while walking the stair. BCBC 9.8.7 covers handrail requirements for residential stairs. Key numbers:

• Height: 865 mm to 965 mm measured vertically from the tread nosing line to the top of the handrail.
• Required on at least one side of a residential stair. Required on both sides above certain widths and in all commercial egress stair configurations.
• Must extend horizontally past the top and bottom riser by at least the depth of one tread (residential). For commercial stairs, the extension requirements are tighter.
• Profile must be graspable — circular sections 32–50 mm in diameter satisfy this without qualification; other profiles need to demonstrate equivalent graspability.

For metal stairs, the handrail attachment point interacts with the stringer, the guard posts, or both. A mono stringer stair with open treads usually mounts the handrail to guard posts that attach to the stringer bracket — so the bracket layout, post height, and handrail offset all need to be resolved together before fabrication. Changing handrail height or profile after steel is cut usually means a field weld, a re-finish strip, and a schedule delay.

Rise, run, and stair geometry

BCBC Section 9.8.4 tables the rise and run requirements for residential stairs in dwelling units:

• Rise: 125 mm minimum, 200 mm maximum per step.
• Run: 235 mm minimum tread depth (not counting nosing overhang).
• Rise + run combinations: The code is a table, not a formula. Verify that the specific rise and run chosen sits inside the compliant zone.
• Variation across a flight: Rise across all steps in a flight must not vary by more than 5 mm from the smallest to the largest riser. This is the clause that causes problems when finished-floor heights are not locked before fabrication — if the top step rises more than the others because the flooring thickness was underestimated, the flight is out of compliance.

For commercial stairs under Part 3, the numbers shift slightly and the AHJ review is more thorough. Minimum tread depth for commercial egress stairs is typically 280 mm per step; minimum riser is typically 125 mm, maximum 180 mm.

Nosing projection on open-tread stairs has its own requirement. BCBC 9.8.4.5 limits tread nosing projection and requires a consistent nosing profile. For floating and open-riser stairs, this affects how far the tread can overhang the bracket and how the nosing profile is finished.

Open risers

Open-riser stairs are popular in modern homes and are permitted under BC Code with conditions. BCBC 9.8.4.6 requires that open risers prevent the passage of a 100 mm sphere. This is effectively the same sphere test as guards. When a tread is cantilevered on a mono stringer with significant spacing between treads, the gap is checked against this limit. Tread thickness and the vertical gap between treads are both part of the geometry review.

For floating or open-riser stairs serving dwelling units, the guard requirements at the sides of the stair and the open-riser limit are reviewed together. Getting one right while ignoring the other is one of the more common reasons a plan review bounces back.

Headroom

Minimum clear headroom over the stair is 1,950 mm measured vertically over the clear width of the stair for residential dwelling units. This measurement runs from the nosing line (the angled line connecting tread nosings) up to the nearest obstruction — typically the underside of an upper floor, a beam, or a sloped ceiling.

On retrofit projects in Vancouver homes with basement stairs, this is frequently tight. A mono stringer with thick concrete-look treads can consume 30–50 mm of headroom that a thinner system keeps. Getting headroom confirmed in drawings before steel is ordered prevents the scenario where the stair clears on paper but fails inspection because finished tread thickness was not accounted for.

Structural connections: the part the code references but custom work drives

The prescriptive code in Part 9 covers residential stairs that land into conventional framing. Custom metal stairs — especially mono stringer and cantilevered designs — ask the structure to do things that the prescriptive code does not directly table. That is when engineering enters the picture.

BCBC 9.8.1 establishes that stairs must be designed to carry the loads imposed on them, including live loads from the guard system. For mono stringer stairs, the two connection points (top landing anchor and bottom floor anchor) are where the entire stair load concentrates. Existing floor framing in Vancouver renovations rarely matches what the drawing assumes.

For Part 3 buildings, Engineers and Geoscientists BC requires that a Designated Structural Engineer seal the structural drawings and sign Schedule B Letters of Assurance before a permit is issued. In our shop, we coordinate the fabrication drawings against the engineer’s drawings before steel is ordered — catching a missed bolt callout in the shop set costs ten minutes; catching it on site costs half a day and a re-inspection.

Part 3 versus Part 9: which rules apply

Part 9 covers housing and small buildings up to a building-area and occupancy threshold. Part 3 covers everything larger — most multi-family, commercial, institutional, and industrial buildings. The practical difference for stair fabrication:

Topic	Part 9 (residential)	Part 3 (commercial/multi-family)
Minimum stair width	860 mm clear	900 mm–1,100 mm+ depending on occupant load
Handrails	One side required	Both sides required (egress stairs)
Engineering stamp	Required for non-prescriptive work	Required for all structural elements
Letters of Assurance	Often not required for simple residential	Schedule B from structural engineer required
Fire rating	Residential separation rules	Rated shaft assembly may be required

The AHJ makes the final call on which Part applies. If the building straddles the threshold, or if the stair crosses between occupancies, confirm the code path before drawings are started.

Permits and documentation

Permit requirements depend on the municipality, building type, and scope. Replacing a decorative railing is not the same as changing a structural stair. Key triggers for a building permit:

• Changing the floor opening size.
• Adding a new stair opening.
• Installing a mono stringer, cantilevered, or floating stair where the connection goes into structural framing.
• Any stair in a Part 3 building.

When in doubt, resolve documentation before fabrication starts. A permit application that lands incomplete is usually delayed by four to eight weeks while corrections are made — longer than the application itself would have taken if the drawings were complete on submission. For more on the permit process and timelines, the staircase replacement permit guide for Vancouver covers the specific city process.

For the installation side of these requirements — how finished-floor heights, structural connections, and trade sequencing actually play out on site — the mono stringer stair installation guide covers the decisions that protect the schedule.

Note on code edition: The 2024 BCBC was issued by the Province of BC and some municipalities in Metro Vancouver have begun adopting it. The stair and guard requirements in Section 9.8 are largely unchanged between the 2018 and 2024 editions, but confirm the edition in force with your authority having jurisdiction before submitting permit drawings.

Sources

• British Columbia Building Code 2018 Division B Section 9.8 — Stairs, Ramps, Landings, Handrails and Guards (accessed 2026-04-09)
• BC Building Code Section 9.8 — guard and handrail summary, buildingcode.online
• Engineers and Geoscientists BC — Designated Structural Engineer
• Province of BC — 2018 Guide to Letters of Assurance (Schedules A, B, C)