What changed for secondary suites
| Topic | 2024 Ontario Building Code |
|---|---|
| Definition | New "secondary suite" definition, with exemptions for houses with up to two suites |
| Separation between units | Smoke-tight barriers allowed instead of fire separations, with conditions such as 5/8" Type X drywall and sealed penetrations |
| Smoke alarms | All smoke alarms in a two-unit house must be interconnected |
| Carbon monoxide alarms | Expanded rules, including interconnection in two-unit houses |
| Ceiling height | Lower minimums allowed for new secondary suites |
| Doors and stair headroom | Doors as low as 1890 mm, stair headroom 1850 mm in suites |
| Exits | The upper unit of a two-unit house may need a separate exit in some cases |
Summary based on the HCRA Ontario Building Code updates and municipal building department bulletins. Your permit reviewer applies the code text itself.
When did the 2024 Ontario Building Code take effect?
It took effect on January 1, 2025. Projects with drawings substantially complete before that date could still apply under the 2012 code until March 31, 2025. Any secondary suite permit applied for today is reviewed under the 2024 code, including legalization permits for existing units.
Other changes that affect houses
- Stairs and guards: openings between treads and the bottom guard rail are limited to 150 mm, and nosings must be rounded or bevelled.
- Ramps: any surface sloped steeper than 1 in 20 is now a ramp.
- Soil gas: new houses need a rough-in for a future depressurization system.
- Sump pits: at least 750 mm deep with 0.25 m² of surface area.
- Ventilation: Part 9 ventilation and duct rules moved to new sections.
What this means for Kingston homeowners
For most Kingston basements, the 2024 code makes a legal suite more achievable. Lower ceiling and door minimums can avoid lowering a floor, and smoke-tight barriers can be simpler than rated assemblies. Interconnected alarms and exits still need careful planning.
We design every unit to the current code and handle the permit for you. See our basement apartment conversions, ARU design and permit service, or the full list of secondary unit services. If you plan to rent affordably, check the Kingston ARU incentives too.
Frequently asked questions
When did the 2024 Ontario Building Code take effect?
The 2024 Ontario Building Code took effect on January 1, 2025. A grace period ran to March 31, 2025 for projects whose drawings were substantially complete before January 1. Permits applied for now are reviewed under the 2024 code.
Do secondary suites still need fire separations under the 2024 code?
For houses with secondary suites, the 2024 code allows smoke-tight barriers instead of rated fire separations, under set conditions such as 5/8 inch Type X drywall and sealed penetrations. Smoke alarms and carbon monoxide alarms must be interconnected between units.
Does the new code apply to my existing secondary suite?
Generally the code applies to new construction, renovations and changes of use, not to existing parts of a building that are left alone. If you are legalizing an unpermitted suite or renovating, the work is reviewed against the current code.
Did the 2024 code make basement apartments easier to build?
In several ways, yes. It allows lower ceiling heights, lower doors and lower stair headroom in new secondary suites, and replaces fire separations with smoke-tight barriers in many houses. These changes can reduce the work needed in older Kingston basements.