Is My Basement Apartment Legal in Ontario? (2026 Guide)

Most Ontario municipalities have allowed at least one secondary dwelling unit in a home since 2019 — but "allowed" doesn't mean "automatic." A basement apartment only becomes legal once it has a building permit and meets a specific set of Ontario Building Code requirements. Here's what actually gets checked.

Ceiling height: habitable rooms need a minimum of 1.95 m (about 6'5"); hallways can be slightly lower. If your basement falls short, underpinning can lower the floor to compliance.

Egress windows: every bedroom needs a window with a minimum unobstructed opening of 380 mm by 760 mm, and the sill can't sit higher than 1,000 mm off the finished floor — an emergency exit large enough for a firefighter in gear, not just a window that lets in light.

Fire separation: the ceiling and walls between the basement unit and the rest of the house need at least a 45-minute fire-resistance rating, interconnected smoke and carbon monoxide alarms, and self-closing doors on any connecting entrances.

If your existing basement apartment is missing one or more of these, it isn't automatically a lost cause — most gaps (a too-small window, an unrated ceiling) are fixable without a full renovation. The first step is always the same: a set of BCIN-certified drawings and a permit application specific to your basement's current layout.

CAUD Group has prepared permit-ready drawings for the GTA & Hamilton (GTHA) homeowners. Book a free assessment and we'll tell you exactly what your basement needs — (647) 667-1270.