Secondary Suites — Building Code Overview
Last updated: June 2026
Fire separation, egress, ceiling height, and smoke alarm requirements for basement apartments.
Detailed explanation
A secondary suite is a self-contained dwelling unit within a house. The OBC and local bylaws regulate when they are permitted and what upgrades are required for legal occupancy.
Typical requirements include fire separation between units, independent egress, minimum ceiling heights, sound transmission limits, and interconnected smoke/CO alarms.
Municipal zoning and licensing rules apply in addition to the OBC. A code-compliant suite still requires local approval.
Ontario Building Code references
Ontario Building Code
Section 9.10.22. — Secondary suites
Specific provisions for suites in houses.
Ontario Building Code
Section 9.5.3. — Ceiling heights
Minimum heights in dwelling units.
Examples
- Converting a basement to a rental suite triggers fire separation between the suite and the main unit.
- A suite may need a separate exterior door or compliant egress window in each bedroom.
Common mistakes
- Renting a basement unit without fire separation or egress upgrades.
- Assuming one smoke alarm is sufficient without interconnection between units.
- Ignoring municipal registration and inspection requirements.
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