BC Building Code 2024: what changed for Part 9 builders

The BC Building Code 2024 took effect on March 8, 2024, replacing the 2018 edition. For a Part 9 builder the changes that matter are: new seismic hazard values that move some sites into higher bracing categories, revised radon and soil-gas provisions, a requirement that every new dwelling unit has one living space that stays at or below 26°C, secondary suites permitted in more building types, updated envelope and ventilation details, and a new base edition that changes which code a permit is reviewed under. Everything else you were doing under 2018 mostly carries on, with renumbered references.

What the 2024 edition is

BC adopts the National Building Code with provincial variations. The 2024 BC Building Code is the 2020 National Code plus BC’s changes: the Energy Step Code and Zero Carbon Step Code, BC-specific seismic and climate data, accessibility and adaptability provisions, and the housing-related changes the province added. It is published by the Building and Safety Standards Branch and available through the province’s building codes and standards pages. The City of Vancouver has its own building by-law that tracks the provincial code with differences; everything below is the provincial code.

The changes, by trade

Structure and seismic

The 2020 National Code adopted a new generation of seismic hazard values, and BC carried them into the 2024 edition. On the coast and on Vancouver Island, design values at many sites went up. For Part 9 that matters in two places. First, the prescriptive bracing provisions in Subsection 9.23.13 are keyed to the site’s seismic category, so a lot that used conventional construction under 2018 may now need braced wall panels laid out to the code, or an engineered lateral design. Second, where the house falls outside the prescriptive limits (irregular shape, large openings, tall walls), the engineer’s numbers are bigger than they were. Get the seismic category confirmed for the site at design, not after the framer has started.

Envelope and moisture

The 2024 edition updates the envelope provisions and the standards it references, but the big envelope requirement for Part 9 remains the Energy Step Code: Step 3 is the base code minimum, with its airtightness test and energy advisor reports. Rainscreen in coastal climates, continuous air barrier detailing and balanced ventilation (HRV or ERV) are what get a house through Step 3 and through a blower-door test. The details are in our Step Code guide and in the moisture and envelope course.

Radon and soil gas

Radon is the change most Part 9 builders have not looked at. The 2024 edition revises the soil-gas provisions and the tables that say where a rough-in for a subfloor depressurization system, or a full system, is required. If you built under the 2018 tables, do not assume your area is still treated the same way. The cost of a rough-in at slab stage is a few hundred dollars of pipe; the cost of retrofitting under a finished basement is thousands. Check the Appendix C tables for your location on every project.

Cooling: the 26°C room

New in 2024: each dwelling unit needs at least one living space designed not to exceed 26°C. This came out of the 2021 heat dome. In practice it means a cooling design for one room (bedroom or living room) or the whole house. A heat pump that already serves as the heating system usually satisfies it; a gas furnace with no cooling does not. Designers need to show the space meets the limit, and mechanical contractors need to size for it. Combined with the Zero Carbon Step Code, this is pushing most new Part 9 houses to heat pumps.

Secondary suites in more building types

Under the 2018 code a secondary suite was only recognized in a single detached house. The 2024 code allows suites in more housing forms, including side-by-side and stacked units, which lines up with the province’s small-scale multi-unit housing changes under Bill 44. Two cautions. The code permitting a suite is not the same as zoning permitting it; the local bylaw still governs. And a suite is still a separate dwelling unit for fire separation, sound rating, exits and smoke alarms, so the Part 9 requirements apply between the suite and the principal unit. See SSMUH and Bill 44.

Permits and the transition

Which edition applies is decided by the permit application date. Applications accepted before March 8, 2024 generally proceeded under the 2018 code; applications after it are reviewed under 2024. That created a long tail of 2018 permits still under construction through 2025, which is why a builder can have two houses on one street under two codes. Watch for the trap in revisions: a significant revision to a 2018-permitted design after the effective date can bring the revised scope under the new code at the building department’s discretion. Ask before you submit.

Enforcement: the Building Act

Since the Building Act, local governments cannot set their own technical building requirements that differ from the code, except in matters the province leaves to them. The Step Code and Zero Carbon Step Code are built into the code precisely so local governments can adopt higher levels by bylaw without writing their own technical rules. Building officials enforce the code; the builder is responsible for compliance. Code-update training is informal CPD under relevant enactments, and it is the competency most builders find easiest to fill with genuinely useful material.

What to do this year

1. Confirm the seismic category for every new lot at design.
2. Re-check the radon tables for your municipality.
3. Put the 26°C room in the mechanical design before pricing the heating system.
4. Check the zoning bylaw before promising a suite in a townhouse or duplex.
5. Note the permit application date on every job so you know which edition you are inspected under.

The 3-hour BCBC 2024 course in the CPD Pass walks through each of these with Part 9 examples and earns 3 CPD points under relevant enactments. Its refresh trigger is any amendment or revision of the code, so a new version is published when the rules move. See the course at BCBC 2024 Part 9: What Changed for Builders.