Egress windows
Every bedroom in a basement suite must have an openable egress window with an unobstructed opening of at least 0.35 m² and no dimension smaller than 380 mm. In practice this means most 1960s– 1990s bungalows need window enlargements and a proper window well.
Ceiling height
Minimum ceiling height for a secondary suite is 1.95 m (about 6′5″) over the required area of each room. Bulkheads and duct drops are allowed to encroach on limited areas.
Fire separation between suites
A 45-minute fire separation is required between the secondary suite and the principal dwelling, typically achieved with one layer of 5/8″ Type X drywall on ceilings and shared walls. All penetrations (plumbing, electrical) must be firestopped.
Interconnected smoke & CO alarms
- Smoke alarms in every bedroom, hallway and on each level.
- Alarms in both dwellings must be interconnected — an alarm upstairs sounds the alarm downstairs.
- CO alarms within 5 m of every bedroom in a suite with fuel-fired appliances or an attached garage.
Ventilation
Each suite needs a mechanical ventilation system that provides fresh outdoor air — usually a bathroom fan with a timer, plus a dedicated outdoor air intake tied to the furnace. HRVs are increasingly common in new legalizations.
Sound attenuation
Party assemblies between suites should meet a Sound Transmission Class (STC) of 50. Resilient channels, Roxul Safe'n'Sound insulation, and double drywall are typical.