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OBC DIVISION B · PART 3 · SECTION 3.1 — APPLICATION

What are the requirements for mixed occupancy buildings in Ontario?

Where a building contains more than one major occupancy, each part must meet the rules for its own occupancy, the most restrictive construction requirements often govern, and major occupancies must be separated by rated fire separations per Table 3.1.3.1.

Code reference
In buildings with multiple major occupancies, each occupancy is subject to its own requirements, and contiguous major occupancies must be separated from each other by fire separations with fire-resistance ratings set out in the Code table, with some combinations, such as high-hazard industrial with assembly or care uses, restricted or prohibited outright.
OBC Division B, Subsection 3.1.3.

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

What this means in practice

Typical examples are retail at grade under residential, or offices over parking. Designers must check the 3.2.2 construction article for each occupancy and apply the more restrictive outcome, then provide the tabulated separation, commonly 1 h to 2 h, between occupancies. Pitfalls include forgetting that a superimposed occupancy can change the sprinkler requirement for the whole building, and overlooking prohibited adjacencies involving Group F Division 1 uses.

Plain language

When one building holds different uses, like shops below apartments, each part follows its own rules and a fire-rated floor or wall keeps them apart. The toughest rule between the uses usually decides how the whole building is built.

Related questions

Which buildings fall under Part 3 of the Ontario Building Code?How is major occupancy classified under the Ontario Building Code?How are building height and building area determined under the Ontario Building Code?

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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.