Free tool Second units Building Code

Basement Apartment Checker: Is Your Basement Ready to Become a Legal Unit?

Measure your ceiling and bedroom window, then work through the five things every Ontario building department looks at before a second unit is approved.

Short version: For a second unit in an existing house, Ontario’s guidance uses a ceiling height of at least 1.95 m over the required floor area and the route to the exit. Bedroom windows commonly need 0.35 m² of clear opening with no side under 380 mm. Zoning, exits, fire separation and alarms, services and parking all have to line up too.

Check your basement

UnitsLowest finished ceiling height over the living area and exit routeBedroom window clear opening width (fully open)Bedroom window clear opening height (fully open)Zoning allows a second unit on your lotYou have a safe exit plan for the unitFire separation and smoke/CO alarms are plannedPlumbing, heating, electrical and septic capacity checkedParking, entrance and registration rules checked

How to use the result

Measure the lowest point of the finished ceiling across the whole required floor area and the exit route, not one spot in the middle of a room.
The age of the house and the scope of work can change which Code path applies; existing houses can sometimes use different ceiling, fire and exit solutions where all conditions are met.
Confirm zoning, servicing, parking, septic, conservation and any municipal registration rules first.

The full rules: Legal basement apartment requirements in Ontario and basement apartment ceiling height.

Questions people ask

What ceiling height does a basement apartment need in Ontario?

For a second unit in an existing house, Ontario’s published guidance identifies a minimum of 1.95 m over the required floor area, including the route to the exit. New construction can have different requirements.

Does a basement bedroom need an egress window?

Commonly yes: at least 0.35 m² of unobstructed opening with no dimension under 380 mm, openable from inside without tools. Check with the egress window checker.

Is this checker a permit approval?

No. It helps you prepare. Your municipality decides, and some houses qualify for alternative solutions.

Related guides on BuildersOntario

Legal basement apartment requirementsThe full Ontario rules Egress window checkerWill the bedroom window pass?Basement apartment ceiling heightHow to measure it Garden suites in OntarioThe other kind of second unit

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Updated November 2026. A planning tool; your building department decides which requirements and alternatives apply to your house.