Insulation, fire & electrical
Required smoke alarms and CO2 alarms in a secondary suite.
Smoke alarms
One smoke alarm in every bedroom.
One smoke alarm outside the sleeping area (typically in the hallway).
At least one smoke alarm on every storey of the dwelling.
Smoke alarms in common/shared areas, such as a shared laundry room or entrance.
Smoke alarms must be hardwired with battery backup in new work and interconnected, so if one alarm sounds, they all sound. For secondary suites, interconnected alarms are required between both the main dwelling and the basement suite.
Carbon monoxide (CO) alarms
CO alarms are required if the house has:
a fuel-burning appliance (natural gas, propane, oil, wood, etc.), or
an attached garage.
They must be installed:
Outside each sleeping area in the basement suite.
In the furnace room, if it is a separate room from the dwelling units.
For a typical legal basement apartment with one bedroom, this usually means:
✅ 1 smoke alarm in the bedroom.
✅ 1 smoke alarm in the hallway outside the bedroom.
✅ 1 CO alarm outside the bedroom.
✅ 1 CO alarm in the furnace room (if it's a separate room with a fuel-burning appliance).
✅ All required alarms are interconnected and hardwired with battery backup.
If you're applying for a permit, I can also provide a complete Ontario Building Code checklist for a legal basement secondary suite, including fire separation, doors, egress windows, HVAC, electrical, and soundproofing requirements.