Ontario building code question

What are the Ontario Building Code requirements for secondary suites?

Ontario has specific OBC provisions for secondary suites covering fire separation, egress, ceiling height, smoke alarms, and plumbing that may differ from the NBC baseline and from municipal zoning bylaws.

Secondary suite requirements in Ontario are governed by the OBC, but the scope of what is permitted also depends on municipal zoning. The OBC sets the building code requirements for fire safety, means of egress, minimum room dimensions, and services, while the municipality determines whether and where secondary suites are allowed. Both layers must be satisfied.

What to check first

  • The OBC has specific secondary suite provisions that may differ from the NBC in fire separation ratings, egress requirements, and ceiling heights.
  • Municipal zoning bylaws determine whether secondary suites are permitted in a given area — the OBC alone does not authorize them.
  • Both new and existing buildings must meet the applicable OBC requirements when a secondary suite is created.

Jurisdiction notes

OBC secondary suite provisions

The OBC includes specific requirements for secondary suites covering fire separation, smoke alarms, egress windows, ceiling heights, and plumbing connections.

Municipal zoning layer

Even when the OBC permits the construction, the municipal zoning bylaw must also allow a secondary suite in the specific location.

Existing building considerations

Creating a secondary suite in an existing building may trigger additional OBC requirements for the existing portions of the house.

Work through it in this order

  1. Confirm that the municipal zoning bylaw permits a secondary suite at the project location.
  2. Review the OBC secondary suite provisions for fire separation, egress, ceiling height, and services.
  3. Identify any additional requirements triggered by the existing building condition.
  4. Document both the OBC and municipal requirements before proceeding with the permit application.

Common questions

Can I build a secondary suite anywhere in Ontario?

Not necessarily. The OBC sets the building requirements, but the municipal zoning bylaw must also permit secondary suites at your specific location.

What fire separation is required for a secondary suite in Ontario?

The OBC specifies fire separation requirements between the secondary suite and the rest of the dwelling. The specific rating depends on the building condition and applicable OBC edition.

Do existing buildings need to be fully upgraded when adding a secondary suite?

The OBC has specific provisions for secondary suites in existing buildings. Some upgrades may be required, but the scope depends on the existing condition and the OBC edition.