Converting your basement into a legal apartment in Ontario is one of the best investments homeowners can make - providing rental income, multi-generational housing, and increased property value. But it must meet specific building code and zoning requirements. Here's everything you need to know for 2026.
Ontario Building Code Requirements
- Ceiling Height: Minimum 1.95m (6'5") in all habitable rooms - if your ceiling is too low, basement underpinning is available
- Fire Separation: 45-minute fire resistance rating between units using fire-rated drywall, doors, and sealed penetrations
- Egress Windows: Minimum 0.35 m² unobstructed opening in each bedroom, with a minimum 380mm dimension
- Smoke & CO Alarms: Interconnected alarms on every level of each unit
- Separate Entrance: Interior shared hallway or exterior separate entrance
- Plumbing: Full kitchen and bathroom facilities required for each dwelling unit
- Heating: Independent heating zone or system for the basement unit
- Ventilation: Adequate ventilation meeting OBC requirements
Zoning Requirements
Since Ontario's 2023 housing policy changes, secondary suites are permitted province-wide in residential zones. In practice most lots can now have up to three residential units as-of-right - the main dwelling plus two additional units such as a basement apartment and a garden suite. However, municipal zoning bylaws still regulate parking, lot coverage, and setbacks, and each city has its own registration process.
Second-Unit Registration
A building permit alone does not make a basement apartment legal - most municipalities also require you to register the second unit after it passes final inspection. In Mississauga, for example, you submit proof of ownership and the signed-off permit to receive a Registration Certificate; Markham requires registration with Fire & Emergency Services. An unregistered unit is not considered legal even if it was built with a permit, which can affect your insurance and financing. We prepare the drawings so both the permit and registration requirements are satisfied.
Egress: The Most Common Sticking Point
Egress is where the most basement apartments fail plan review. Each bedroom needs an openable window with an unobstructed opening of at least 0.35 m² (about 3.8 sq ft) and no dimension less than 380 mm, operable without tools or special knowledge. If the window is below grade, a window well of adequate size is required. Where a compliant window is not achievable, a separate walkout entrance can provide the required means of escape.
The Permit Process, Step by Step
- Zoning check - confirm your lot conforms, or apply for a minor variance
- BCIN drawings - a complete set showing fire separation, egress, ceiling heights, and independent HVAC, typically ready in 5–10 business days
- Submit to the city - through the municipal portal, with Schedule 1 and energy compliance
- Inspections & registration - build with inspections at each stage, then register the unit
See our full Ontario permit process guide for details.
What a Legal Basement Apartment Costs
BCIN designer fees for basement apartment drawings typically range from $2,000 to $4,000, with underpinning or a walkout entrance adding to the total. Municipal permit fees are separate. See our 2026 building permit cost guide for a full breakdown.
Common Reasons Basement Apartments Get Rejected
- Ceiling height below 1.95 m with no underpinning proposed
- Bedroom egress windows too small or not openable without tools
- Incomplete fire-separation details between the units
- No independent ventilation or heating for the suite
- Zoning non-conformance (parking, unit size, or a second unit not permitted on that lot)
If your project has already been turned down, we can fix and resubmit it - see Permit Rejected? We Can Help.
Specific City Resources
Ready to get started?
Call 416-558-9607 for a free consultation or request a quote online.
Related Resources
- Legal Basement Apartment Permit Drawings
- Building Permit Drawing Cost Guide
- How to Legalize Unpermitted Work
Frequently Asked Questions
What is the minimum ceiling height for a basement apartment in Ontario?
The Ontario Building Code requires a minimum ceiling height of 1.95 metres (6'5") in all habitable rooms. If your basement is lower, underpinning may be required.
Do I need fire separation for a basement apartment?
Yes. The OBC requires a 45-minute fire resistance rating between dwelling units. This includes fire-rated drywall on ceilings and shared walls, fire-rated doors, and sealed penetrations for pipes, ducts, and wiring.