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OBC DIVISION B · PART 9 · SECTION 9.35 — GARAGES AND CARPORTS

What gas-proofing is required between an attached garage and the house in Ontario?

The wall and ceiling between an attached garage and the dwelling must form a continuous air barrier against carbon monoxide and fumes, with any connecting doorway fitted with a tight, weatherstripped, self-closing door, and no door opening into a sleeping room.

Code reference
Where a storage garage is attached to or built into a dwelling, the separating construction must be sealed with an air barrier system to prevent vehicle exhaust and gasoline vapours migrating into living space. A doorway between garage and dwelling must have a self-closing, weatherstripped door, must not lead directly into a bedroom, and penetrations through the separation must be sealed.
OBC Division B, Article 9.10.9.16.

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

What this means in practice

This is a life-safety detail aimed at carbon monoxide, and it is scrutinized at insulation and final inspections. Tape or seal the poly or airtight drywall across the whole shared wall and ceiling, foam every wire, pipe and duct penetration, and remember ducts should not serve the garage from the house system. The man-door needs functioning self-closing hardware, which owners notoriously disable. Pair the sealed separation with the carbon monoxide alarm requirements that apply to dwellings with attached garages, since the alarm is the backup, not the primary defence.

Plain language

The wall between your garage and your home has to be sealed airtight so car exhaust cannot seep inside, and the connecting door must close itself firmly. Carbon monoxide is invisible, so the code treats this joint seriously.

Related questions

What are the foundation and floor slab requirements for garages in Ontario?What is the difference between a carport and a garage 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.