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OBC DIVISION B · PART 3 · SECTION 3.18 — ADDITIONAL REQUIREMENTS FOR EXISTING BUILDINGS

What upgrades are required when changing the use of an existing building in Ontario?

A change of major occupancy, converting a warehouse to offices or a house to a daycare, requires a permit even without construction, and triggers assessment of fire safety, structural adequacy and life safety systems, with upgrades where the new use imposes greater hazard or loads.

Code reference
Where the use of an existing building changes to a different major occupancy or otherwise increases hazard, the Code requires the building to be assessed against the requirements applicable to the new use, with upgrades where the change increases hazard, including fire separations, means of egress, fire protection systems and structural capacity for the loads of the new occupancy.
OBC Division B, Section 3.18; Part 10 (Change of Use) and Part 11

Paraphrased for clarity — open this provision in the BUILDAiD Library for the exact wording.

What this means in practice

Change of use is regulated because risk lives in the occupancy, not the construction: the same floor plate is far more dangerous as an assembly space than as storage. Ontario's Part 10 governs change of use permits, using hazard comparisons between old and new occupancies to scale required upgrades, with Part 11 and Section 3.18 supplying the compliance mechanics for Part 3 buildings. Common surprises include structural checks for heavier live loads, sprinkler and fire alarm obligations, and barrier-free upgrades. Budget a code consultant's assessment before signing the lease.

Plain language

Turning a warehouse into a gym, or a house into a daycare, needs a permit even if you change nothing physically, because more people at higher risk will be inside. The city checks whether exits, fire safety and structure suit the new use, and may require upgrades.

Related questions

What triggers the additional Part 3 requirements for existing buildings in Ontario?What compliance alternatives exist for existing buildings under the Ontario Building Code?How does Section 3.18 relate to Part 11 renovation rules in Ontario?

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This page is provided for general information. Building code requirements depend on your specific project, occupancy and municipality, and code editions change. Always verify requirements against the current Ontario Building Code and confirm with your local building department.