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OBC DIVISION B · PART 3 · SECTION 3.2 — FUNCTIONAL STATEMENTS / BUILDING FIRE SAFETY

When is noncombustible construction required under the Ontario Building Code?

The construction articles in Subsection 3.2.2 set permitted construction by occupancy, building height, building area, sprinklering and streets faced. Larger and taller buildings must be noncombustible, while smaller ones may use combustible or encapsulated mass timber construction.

Code reference
For each major occupancy, a matrix of articles defines maximum building height and area for combustible construction, encapsulated mass timber and noncombustible construction, together with required fire-resistance ratings for floors, roofs and supporting members and whether a sprinkler system is mandatory for the configuration chosen.
OBC Division B, Subsection 3.2.2.

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

What this means in practice

Selecting the governing 3.2.2 article is a foundational step: it fixes structure type, fire-resistance ratings and usually the sprinkler decision in one move. Ontario permits encapsulated mass timber for certain buildings up to 12 storeys, which has expanded wood options for mid-rise work. Common errors include using gross floor area instead of building area, miscounting storeys because of grade, and missing the requirement that heavy timber or combustible elements still need specific ratings.

Plain language

Small buildings can be built of wood, but as buildings get bigger and taller the Code requires materials that will not burn, like concrete and steel, or specially protected mass timber. Size, height, use and sprinklers all feed into that decision.

Related questions

When are automatic sprinklers required in a building in Ontario?What are the fire department access route requirements under the Ontario Building Code?When is a fire alarm system required in a building 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.