Commercial egress stair systems

Commercial and institutional stairs in British Columbia are governed by Section 3.4 of the BC Building Code (Means of Egress). The specific requirements depend on building occupancy (Group A assembly, Group B institutional, Group D business, etc.), occupant load, building height, and whether the stair is interior or exterior. Section 3.4 sets minimum stair width based on occupant load, riser/run dimensions, landing requirements, fire separation, and handrail standards.

Stair width is calculated from occupant load. For most assembly and business occupancies, BCBC 3.4.3.2 sets the minimum exit width at 9 mm per person for stairs with risers up to 180 mm and runs at least 280 mm. For a stair serving 100 occupants, that is 900 mm minimum — but in practice, most commercial stairs are built at 1100 mm (44 in) or wider to allow simultaneous two-way movement and to provide capacity headroom.

Required egress stairs in most commercial and institutional buildings have to be enclosed in a fire-rated shaft. The rating depends on building height — typically 1 hour for buildings up to 6 storeys and 2 hours for taller buildings. The stair structure itself usually needs to be non-combustible (steel or concrete). Stair components (treads, risers, stringers, handrails, guards) made of structural steel meet the non-combustible requirement directly.

Yes, in most cases. BCBC 3.4.6.5 requires handrails on both sides of any stair more than 1100 mm wide, and on both sides of all egress stairs in commercial occupancies regardless of width. Handrails have to be continuous through landings, mounted 865–965 mm above the nosing, with returns at the top and bottom that meet the wall or post.

Commercial egress stairs require structural engineering by a P.Eng. licensed in British Columbia. The engineer reviews the stair structure for the BC Building Code load requirements (4.8 kPa live load for stairs in assembly occupancies, 4.0 kPa for most other commercial), sizes the stringers and connections, and seals the shop drawings. We coordinate directly with the project structural engineer on every commercial stair we fabricate.

Egress stairs are the required means of escape in a fire or emergency — they have to meet BCBC Section 3.4 requirements for width, enclosure, fire rating, handrails, lighting, and signage. Convenience stairs connect floors inside a building but are not required for egress. Convenience stairs have fewer code restrictions and can take more architectural liberties (open stringers, glass railings, feature designs). Most commercial buildings need both types.

BCBC Section 3.4 specifies the number of exits required based on occupant load, building area, and building height. Most commercial buildings above a certain size need at least two independent egress stairs, located so occupants have alternative escape routes. Tall buildings and buildings with higher occupant loads need more. The architect or code consultant determines the exact number during design.

Interior egress stairs in most commercial and institutional buildings are painted steel or powder-coated steel. The colour is usually neutral (grey, beige, off-white) to match the stair shaft interior. High-traffic institutional stairs sometimes get a more durable coating system. Exterior egress stairs are galvanized. High-end lobby stairs in architectural areas (not required egress stairs) may be stainless or have custom finishes.

The structural steel itself is non-combustible — it won't burn — but unprotected structural steel loses strength at high temperatures. For fire-rated stair assemblies, the code may require fire-resistive protection on the structural members (spray-on fireproofing, intumescent paint, or enclosure in fire-rated drywall). The rating (typically 1 or 2 hours) is how long the assembly has to maintain structural capacity during a standard fire test. We fabricate the structure; the fireproofing is usually applied on site by a separate trade.

A concrete-filled metal pan is a formed steel pan (usually 16–14 gauge) that gets concrete poured into it on site after the stair structure is installed. The concrete provides the tread surface — durable, fire-rated, matches surrounding concrete flooring. This is the standard tread system for most commercial egress stairs because it's cost-effective, fire-rated, and holds up to heavy use. Alternatives include precast concrete treads, stone, and for industrial applications, bar grating or checker plate.

Stair assemblies are typically delivered in prefabricated sections — often one flight between landings as a single weldment. Each section is crane-lifted or hand-set into position, then bolted or field-welded to the supporting structure at top and bottom. Field welding is done by qualified welders under the same CSA W47.1 procedures used in the shop. Installation of a single flight usually takes a half-day to a full day per flight.

Stairs themselves are not accessible — that's what elevators and ramps are for. But the stair has to meet specific accessibility requirements for the handrails (continuous through landings, extensions at top and bottom, specific diameters and profiles), contrast marking at the nosings (visual indication for people with low vision), and tactile warnings at the top of the flight. BCBC and the BC Building Access Handbook cover these requirements. We detail them on shop drawings.

Rarely for egress. Open-riser stairs (where you can see through the gap between treads) are restricted by code in most commercial occupancies because they don't prevent small children from crawling through and because debris can fall through. Some occupancies allow open risers if the gap is smaller than 100 mm. Convenience stairs in private commercial spaces (offices, restaurants) have more flexibility.

For commercial projects, we provide a closeout package that includes as-built drawings reflecting any field changes, weld procedure specifications used on the project, welder qualification records (CWB certificates), material certifications (mill test reports for structural sections), galvanizing or finish certifications, and warranty information. Everything gets delivered to the GC for inclusion in the project manual.