Basement apartment building code rules in Ontario: what the inspector checks

The permit process gets the paperwork right. The rules below are what the building inspector actually measures on site. The numbers are for a basement unit added to an existing house that is more than five years old. Newer houses have stricter rules in a few places, which we point out.

1. Ceiling height

The unit needs at least 1.95 m (about 6′5″) of clear height, and at least 1.85 m (about 6′1″) under beams and ducts. Measure before you buy anything. Low ductwork is the most common surprise, and it is far cheaper to reroute a duct on paper than after the drywall is up.

2. Bedroom egress windows

Every bedroom needs a second way out, unless the unit has its own door straight to the outside. An egress window must:

• open from the inside without tools or keys;
• give at least 0.35 m² of clear opening, with no side narrower than 380 mm (about 15″);
• stay open on its own;
• leave at least 550 mm of clear space in front if it opens into a window well.

Many older basement windows are too small, so this often means cutting the foundation for a larger window and a proper well.

3. Fire separation between the two units

Fire and smoke must not be able to move quickly from one home to the other. In an existing house this usually means:

• 15.9 mm (5/8″) Type X fire-rated drywall on the basement ceiling, or a ceiling assembly rated for 30 minutes;
• Type X drywall on walls shared with the upstairs unit, including the underside of the stairs;
• a solid-core door at least 45 mm thick, with a self-closer, between the units.

Regular drywall does not count as fire-rated, even in two layers.

4. Smoke and carbon monoxide alarms

• Smoke alarms on every storey, in every bedroom and in the hallway outside the bedrooms.
• All alarms interconnected, wired or wireless, so one alarm going off sounds every alarm in the house, upstairs and down.
• Carbon monoxide alarms next to sleeping areas when the house has a fuel-burning appliance (gas furnace, water heater or fireplace) or an attached garage.

5. Heating and ventilation

In a house over five years old, the existing furnace can serve both units if a smoke detector is installed in the ductwork to shut the furnace down when it senses smoke. A house under five years old needs a separate system for the new unit so air is not shared. Either way, the unit needs proper mechanical ventilation.

6. Exits and the side entrance

One exit is enough if it belongs only to the unit: a side or rear door, a walk-up or a walk-out. If the unit shares the inside stairs, those stairs must be separated from the main house by a fire separation.

Brampton’s zoning adds two rules for a side or rear entrance: a 1.2 m clear path to the front entrance, entirely on your property, and a landing less than 0.6 m above the ground. See our page on basement separate entrances.

7. Sound between the units

In a house under five years old, the walls and floor between the units need a sound rating of at least STC 43. Older houses are exempt, but insulating the ceiling is cheap while it is open, and both households will notice the difference.

What it costs to apply in Brampton

The City’s two-unit package lists a $200 registration fee and a $1,186.24 permit fee. Fees are updated from time to time, so confirm the current amounts before you apply.

The drawings must come from a BCIN-qualified designer, an architect or engineer, or the homeowner taking legal responsibility for the design. Our BCIN designer prepares the drawings in-house, and the same team builds to them. Read what a BCIN designer is, or follow the step-by-step legal basement checklist.

Sources: City of Brampton – Additional Residential Units and its Two-Unit Dwelling package; Ontario Building Code guide to basement secondary suites (Div. B 9.5.3, 9.9.10.1, 9.10.19, 9.32.3.9A, 9.33.6.13). This is a plain-language summary, not legal advice. Requirements depend on your house, so we confirm them for your address during a free assessment.