Every Vancouver Stairs build is designed to BC Building Code.
Part 9 residential, Part 3 commercial. Engineer-stamped on request. We flag non-compliant existing stairs before we quote a replacement — because the cheapest thing about a custom stair is doing it to code the first time.
Most failed stairs in BC were not built wrong on purpose.
They were built without anyone checking the code clauses that applied. Guards that look fine until a child leans on them and the infill spacing turns a 100 mm sphere rule into a real-world hazard. Risers that vary 12 mm across a flight because the framer cut for the rough opening, not the finished tread. Open-riser stairs that were never reviewed for the 9.8.4.6 sphere rule. None of these are exotic problems — they're the everyday consequence of skipping the code review.
Vancouver Stairs runs the BC Building Code review at shop drawing stage, before steel is cut. For Part 3 commercial work and for most custom Part 9 residential geometry, a structural engineer of record stamps the connections and structural elements under Schedule B. CWB-certified welds (CSA W47.1, Division 2) back the stamp on the fabrication side.
This page is the plain-English reference for the clauses we see most. It is not legal advice and it is not a substitute for a current copy of the BC Building Code or a conversation with your authority having jurisdiction (AHJ) — always confirm the adopted edition and any local amendments with your municipality before fabrication.
Part 9 vs Part 3.
The BC Building Code splits stair requirements by building size and use. Get the part right before you draw anything.
Houses and small buildings.
Up to 3 storeys, up to 600 m² building area per floor. Single-family homes, duplexes, most small multi-family, small commercial. Guards 900 mm minimum (1070 mm where over 1.8 m drop). Run 210–355 mm, rise 125–200 mm. Open risers permitted with sphere-rule infill.
Larger and high-occupancy buildings.
Anything over Part 9 limits, plus all assembly, care, and high-hazard occupancies regardless of size. Guards 1070 mm minimum. Run 280 mm minimum, rise 125–180 mm. Fire-rated enclosed exit stairs. Handrails on both sides above certain widths. Engineer's stamp essentially always required.
Rise, run, width, headroom.
What the code allows — and what we recommend within that range.
Part 9 residential. Rise 125–200 mm, run 210–355 mm (255 mm is the comfort sweet spot), minimum stair width 860 mm for the main stair to a dwelling unit, headroom 1950 mm minimum. Riser height must be uniform within 5 mm across a flight. Tread depth uniform within 5 mm. Nosing projection limits apply on open risers under 9.8.4.5.
Part 3 commercial. Rise 125–180 mm, run 280 mm minimum, width sized to occupant load (1100 mm typical minimum), headroom 2050 mm minimum. Treads and risers within 5 mm uniformity. Slip-resistant nosing required. Tactile attention indicators at top of exit stairs in many occupancies.
What we recommend within the range. 178 mm rise, 280 mm run, 1100 mm width on residential mains where space allows — comfortable for ascent, generous on descent, and reads as deliberate next to the framed dimension. On Part 3 work we default to 1200 mm widths unless the occupant load drops the minimum further.
The 900 / 1070 / 100 numbers.
Three numbers we resolve at shop drawing stage.
- 900 mm — minimum guard height on Part 9 stairs where the drop below is less than 1.8 m.
- 1070 mm — minimum guard height on Part 9 stairs where the drop is 1.8 m or more, and the default minimum on Part 3 stairs.
- 100 mm sphere rule — no opening in a guard, on a stair or otherwise, may allow a 100 mm sphere to pass. This applies to picket spacing, cable infill, glass-panel gaps, and the geometry around the bottom of a guard against the tread.
- Handrails — required on at least one side of every stair with three or more risers (Part 9) or both sides above 1100 mm width (Part 3). Graspable profile: 32–51 mm diameter or equivalent. Continuous along the flight. Returns to the wall or to a post at terminations.
The 100 mm sphere rule on open-riser stairs.
Floating, mono stringer, and cantilevered stairs all live or die by this clause.
BCBC 9.8.4.6 says the opening between adjacent treads on an open-riser stair must not allow a 100 mm sphere to pass through. That sounds simple, but the geometry depends on rise, nosing projection, and the angle the sphere is tested at — straight through, not just horizontally. A 178 mm rise with no fascia and no nosing detail will pass the rule on most flights; a 195 mm rise with a thin tread profile usually won't, and needs a fascia, a sub-rail, or a tread shape adjustment.
We resolve this on the shop drawing before steel is cut. The fix is almost never expensive at that stage; it becomes expensive when it's discovered at inspection on an installed stair.
When a stair needs Schedule B in BC.
Schedule B is a structural engineer's letter committing to review and inspection of structural elements.
Almost always required: cantilevered stairs (wall-anchored treads), mono stringer stairs (single central beam), open-riser stairs over a certain rise, curved or helical stairs, any stair that changes a structural opening, any Part 3 commercial stair.
Sometimes required: conventional double-stringer residential stairs in renovation work, especially where the upper landing or lower base plate ties into existing framing. Most Metro Vancouver municipalities default to requiring a stamp on any custom steel stair touching the building structure.
We don't stamp our own structural drawings — that letter comes from the project engineer. What we provide: field-measured geometry, connection details, weld procedure data sheets (under our CWB W47.1 Division 2 certification), and shop drawings the engineer can review and seal. That's the package the inspector eventually signs off against.
5 code violations we find on Vancouver tear-outs.
Patterns we see repeatedly when quoting stair replacements.
- Guards below 900 mm. Most common on 1970s–1980s homes where the guard was framed to a 36-inch (914 mm) intent but settled or was rebuilt to less. Any reno that touches the guard triggers a current-code rebuild.
- Open-guard infill that fails the 100 mm sphere rule. Original horizontal-rail guards with 6–8 inch spacing. They never passed when built and don't pass now.
- Riser height variation greater than 5 mm. Almost universal on stairs the framer built directly on the rough framing without a finished-tread layout. The bottom riser is short, the top riser is tall, and the middle is fine — trip hazard documented in code commentary.
- Headroom under 1950 mm where a soffit or beam crosses the stair run. Common in finished basements where the duct was dropped after the stair was framed.
- Handrails that don't return to the wall. A handrail that terminates in open space catches sleeves and bags — code requires a return for that reason. Often missed on retrofits.
When we quote a replacement, we flag whichever of these we see on the existing stair, and the quote includes the geometry adjustment needed to bring the replacement into compliance. You shouldn't find out at inspection.
Get a BC Code review with your quote.
Send us the basics — stair type, dimensions, address, drawings if you have them — and we'll respond within one business day with the BC Code clauses that apply, any compliance concerns we see, and a ballpark range. No charge.
BC Building Code for stairs — common questions.
What is the BC Building Code requirement for stair guard height?
Residential stair guards must be at least 900 mm above the tread nosing, and at least 1070 mm where the stair is over 1.8 m above the finished floor below (BCBC 9.8.8). Part 3 commercial buildings require 1070 mm minimum guards on stairs and 1070–1100 mm at landings depending on occupancy. Guard infill must prevent a 100 mm sphere from passing through any opening.
Do open-riser stairs meet BC Building Code?
Yes, when the riser opening is detailed correctly. BCBC 9.8.4.6 limits open-riser openings so that a 100 mm sphere cannot pass through. Most custom mono stringer and floating stairs in Metro Vancouver meet this either by limiting riser height geometry, by adding a fascia detail behind the tread, or by integrating a horizontal sub-rail between treads. We resolve this at the shop drawing stage, before fabrication.
When does a residential stair need an engineer's stamp in BC?
Almost always for custom geometry. Most Metro Vancouver municipalities require a Schedule B engineer's letter for cantilevered, floating, mono stringer, open-riser, or curved stairs, or whenever the stair changes a structural opening. Standard prefabricated stairs in conventional framing usually do not, but custom steel stairs that anchor into the building structure do. We coordinate with your structural engineer of record.
What is the difference between Part 9 and Part 3 of the BC Building Code for stairs?
Part 9 covers houses and small buildings up to 3 storeys and 600 m² per floor — most single-family homes and small multi-family projects. Part 3 covers everything larger and all assembly, care, and high-hazard occupancies. Part 3 stairs have stricter guard heights, fire-rating requirements for enclosed exit stairs, mandatory handrails on both sides above certain widths, and additional accessibility requirements. We design to the part that applies to your building.
What stair dimensions are required by the BC Building Code?
Part 9 residential stairs: rise 125–200 mm, run 210–355 mm (255 mm preferred), minimum width 860 mm for the main stair, headroom 1950 mm minimum. Tread depth must be uniform within 5 mm across a flight, riser height within 5 mm. Part 3 commercial: rise 125–180 mm, run 280 mm minimum, width per occupant load with 1100 mm typical minimum, headroom 2050 mm. Always confirm the current adopted code edition with your AHJ.
Are mono stringer stairs allowed under BC Building Code?
Yes. A mono stringer stair is a structural support method, not a code category. It complies when the stringer, the tread connections, and the guard system are designed and engineered to meet the relevant Part 9 or Part 3 provisions and the 100 mm sphere rule on open risers. Every mono stringer stair we build is reviewed by a structural engineer for the connections and base plate.
What are the most common BC Code violations on existing residential stairs?
Five we see repeatedly on tear-outs: (1) guards below 900 mm height; (2) open-guard infill that lets a 100 mm sphere pass; (3) riser height variation more than 5 mm across a flight; (4) headroom under 1950 mm where a soffit or beam crosses the run; (5) no handrail or handrails that don't return to the wall. Any of these can fail an inspection on a renovation, even if the stair has been in place for decades.
Who certifies that a stair meets BC Building Code?
Three parties share responsibility. The structural engineer of record provides the Schedule B letter for connections and structural elements. The fabricator (Vancouver Stairs, CWB-certified) certifies the welds and the fabrication match the engineered drawings. The municipal building inspector confirms the installed stair meets the code on site inspection. We provide shop drawings, weld procedure data sheets, and as-built dimensions so each party can sign off cleanly.