Multiplex Staircase Requirements in Vancouver: A Developer's Guide

Small multiplex projects put a stair scope in front of fabricators that single-family infill never did. Here is what changes when a stair serves three, four, or six units instead of one.

This article is fabrication context, not engineering or permit advice. Code interpretation and permit scope belong with the authority having jurisdiction (AHJ) and the project’s licensed professionals. Confirm applicability with the local building department before finalizing design or permit submissions.

Small-scale multi-unit housing has changed what a stair scope looks like on a former single-family lot. A three- to six-unit multiplex under BC’s small-scale multi-unit housing framework needs a stair that serves more than one dwelling unit, and that single change moves the project out of several width, guard, and handrail exemptions that apply to a single-family house.

Multiplex zoning created a new stair scope

BC’s small-scale multi-unit housing legislation, enacted through Bill 44 in 2023, requires municipalities over 5,000 people to permit at least three units on lots of 280 square metres or less, and at least four units on larger lots, with up to six units allowed near frequent transit service. Local governments were required to update their zoning bylaws to reflect these minimums by June 30, 2024.

That deadline is now more than two years old. It already changed what gets built on former single-family lots across Vancouver, Burnaby, New Westminster, and neighbouring municipalities. A lot that previously supported one house with one exterior stair now often supports three, four, or six units, several of which share a stair or a landing.

For a fabricator, the practical shift is this: a stair drawn to single-family assumptions, meaning the width, guard height, and handrail rules that apply to a stair serving one dwelling unit, does not automatically satisfy the code once that same stair serves a second or third unit. The building official reviewing the permit checks the stair against the classification the building actually has, not the classification the previous house on the lot had.

Shared stairs lose the single-unit width exemption

BC Building Code Part 9 sets two different minimum stair widths depending on what the stair serves. An exit stair serving a single dwelling unit needs a clear width of not less than 860 mm. Required exit stairs and public stairs serving buildings of residential occupancy generally need a clear width of not less than 900 mm.

That 40 mm difference sounds small. It isn’t the only thing that changes. The single-dwelling-unit exemption in Part 9 also relaxes handrail continuity, tactile warning strips, and the load the stair is designed to carry. Once a stair serves more than one unit, none of those exemptions apply by default, and the stair gets reviewed against the standard multi-unit provisions instead.

A multiplex with private ground-level entries per unit can sometimes keep each stair in the single-unit category, if each stair genuinely serves only its own unit’s entry. A multiplex with a shared landing serving two or more front doors, which is a common configuration on narrower infill lots, puts that stair in the multi-unit category from the first sketch. The unit layout decides this, not the total number of units on the lot. Confirm the classification for each specific stair run with the project’s designer and the authority having jurisdiction before finalizing the layout.

Guard height depends on which unit rule applies

Guard height follows a similar split. BC Building Code Part 9 sets guards not less than 900 mm high for exterior guards serving no more than one dwelling unit, provided the walking surface is not more than 1800 mm above the finished ground level. Guards in other cases, including most shared multiplex stairs, need to be not less than 1070 mm high.

The 1070 mm figure is not a large jump from 900 mm. But it changes the picket or infill layout and the baluster spacing calculation, since BC Building Code Part 9 also requires guard openings sized to prevent the passage of a 100 mm sphere. A guard drawn at 900 mm for a single-family stair and reused on a shared multiplex landing without adjustment is one of the more common gaps a plan reviewer catches.

Interior guards within any dwelling unit, single or multiplex, are permitted at 900 mm regardless of the exterior classification. The distinction that matters for a shared exterior stair is whether that stair serves one unit or more than one, and whether the walking surface it protects sits above or below the 1800 mm threshold.

Handrail continuity changes on a shared stair

A stair serving a single dwelling unit is permitted a handrail that starts from a newel post or volute installed on the bottom tread, rather than running fully continuous. BC Building Code Part 9 requires at least one continuous, graspable handrail for stairs serving more than a single dwelling unit, running the full length of the flight including at the landing except where interrupted by doorways.

For fabrication, this means the handrail return and termination details on a shared multiplex stair need to be resolved before the guard panels are shop-fabricated, not adjusted on site. A continuous handrail also needs to terminate by extending not less than 300 mm beyond the top and bottom of each flight, another provision that does not apply to a single-unit stair.

Handrail height itself does not change with unit count. Part 9 sets required handrails between 865 mm and 1070 mm measured vertically from a line tangent to the tread nosings, and that range applies whether the stair serves one unit or six.

Exterior stair height limits shape the site plan

BC Building Code Part 9 limits the vertical height of any single flight of stairs to 3.7 m, a limit that applies regardless of how many units the stair serves. On a sloped multiplex lot, that ceiling often forces an intermediate landing partway up the grade change rather than a single long run from the sidewalk to the entry level.

This matters earlier than most developers expect. Where the site plan puts a shared entry above a parking level or above a grade change greater than 3.7 m in one run, the stair needs at least one landing, and that landing needs its own footing, guard, and structural connection back to the building. Working that landing location out during schematic design, rather than after the framing package is locked, keeps the stair fabrication scope predictable.

Exterior concrete steps with more than two risers and two treads also need specific support, either bearing on unit masonry or concrete not less than 150 mm in cross-section, or cantilevered from the foundation wall with the anchorage and frost protection detailing that cantilevered systems require. A steel stair sidesteps some of that concrete-step detailing, but the landing-to-foundation connection still needs engineering coordination regardless of material.

Loading requirements shift once a stair serves multiple units

BC Building Code Part 9 sets a minimum design load of 1.9 kPa for stairs and ramps serving no more than one dwelling unit, and 4.8 kPa for other stairs and ramps. A shared multiplex stair generally falls into the 4.8 kPa category, since it is not serving a single unit.

That load difference changes the stringer section, the connection hardware, and sometimes the tread material itself. A stringer sized for a single-family exterior stair at the lighter loading assumption is not automatically adequate once the same run is re-scoped to serve three or more units. This is a structural engineering calculation, not a fabrication judgment call, so the stair’s engineer of record needs to confirm the applicable loading category before shop drawings are issued.

Fabricators coordinate stair scope against the framing and permit timeline

In our shop, the multiplex projects that stay on schedule are the ones where the stair scope gets locked before the framing package goes out for pricing. Not after. A shared stair that gets re-drawn from a single-unit assumption to a multi-unit assumption partway through framing usually means a wider opening, a different landing footprint, or a heavier connection than the framer priced.

In most of the projects we see, the fabricator gets the architectural drawings, the structural engineer’s load and connection requirements, and the site grading plan at the same time, so the stair opening dimensions and landing heights match what actually gets built. Waiting until permit issuance to bring in a fabricator often means the stair location or width shown on the drawings does not match what the framed structure can accommodate without rework. The permit and engineering process page covers how shop drawings and engineering review typically fit into that sequence.

Lead time for an engineered multi-unit exterior stair depends on stringer section, finish, and shop load, and it should be confirmed with a current quote rather than assumed from a single-family project timeline. A galvanized or powder-coated stair serving a shared multiplex landing typically carries more engineering review than a single private stair, which is a schedule input worth raising with the fabricator early rather than after steel is meant to be on site.

What this means for the next multiplex on the boards

A stair that would have been straightforward on a single-family lot needs a second look once the same site becomes a three- to six-unit multiplex. Width, guard height, handrail continuity, and design loading all shift once a stair serves more than one dwelling unit, and a plan reviewer checks the drawings against that classification, not the site’s previous single-family history.

For egress stair design on larger commercial and mixed-use projects, similar principles apply at a bigger scale. Background on how BC code applies to commercial stairs is useful context for any multiplex that blends residential and shared common-area circulation.

Sources

• Small-scale, multi-unit housing, Province of British Columbia
• BC Building Code 2018, Division B, Section 9.8: Stairs, Ramps, Handrails and Guards
• Building code updated to support more homes in B.C., Province of British Columbia

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Multiplex stair scopes get resolved fastest when the fabricator sees the architectural drawings, the structural load requirements, the site grading plan, and the target permit date at the same time as the framer. Send those alongside the unit layout, so it is clear early which stairs on the site serve one unit and which serve more than one.