Homeowner Guide· Updated November 2026· Reviewed by ProScore Editorial Team

Finishing a Garage in Ontario: Drywall, the Building Code and Cost

What Ontario code requires between an attached garage and a house (it is not fire-rated drywall), what drywalling a garage costs, permits, and carbon monoxide alarms.

To finish an attached garage in Ontario, the wall and door between the garage and the house matter most. They must stop car exhaust and other gases from getting into your home. For a garage that serves only your own house, the Ontario Building Code does not require a fire-rated wall there. It requires an air barrier against gas and exhaust fumes, and a tight-fitting, weather-stripped, self-closing door. Drywall itself costs about $2 to $4 per square foot to hang and finish in Ontario.

This guide covers what the code asks for, what fire-rated drywall does and does not do, what finishing costs, and when you need a permit.

Does the Wall Between a Garage and a House Need Fire-Rated Drywall in Ontario?

Not for a garage that serves only the house it is attached to. Ontario's Building Code, the 2024 edition in force since January 1, 2025, says a storage garage serving only the dwelling it is attached to is considered part of that dwelling, so the fire separation that applies to other garages need not be provided (Article 9.10.9.18).

What the code does require, where a garage is attached to or built into a house (Article 9.10.9.18):

•An air barrier system between the garage and the rest of the house that is an effective barrier to gas and exhaust fumes.

•Sealed, supported joints where a membrane provides the airtightness.

And for the door (Article 9.10.13.15):

•Tight-fitting and weather-stripped, so gas and exhaust fumes cannot pass.

•A self-closing device, so the door closes on its own.

•Not in a bedroom. The doorway between the garage and the house cannot be in a room intended for sleeping.

Many guides online still say fire-rated drywall is required, or cite the older code's article numbers. For a garage shared by more than one home, such as a house with a separate unit, the rules are different: the code requires a fire separation in other cases, so ask your building department.

What Is Fire-Rated (Type X) Drywall For?

Type X drywall is made to resist fire for longer than regular board, and it is used where the code calls for a rated fire separation. Using it in your garage is a choice, not a requirement for a single house. It does not replace the air barrier: a fire-rated wall with gaps around outlets, pipes and the attic hatch can still let exhaust into the house.

Whatever board you choose, the work that protects your family is the sealing:

•Seal every gap in the shared wall and ceiling: around electrical boxes, pipes, ducts and the edges of the drywall.

•Do not leave the attic open above a garage that shares an attic with the house.

•Check the door every year: replace worn weather-stripping and make sure the closer still pulls the door shut and latches.

How Much Does It Cost to Drywall a Garage?

Our Ontario drywall cost guide puts drywall at $2 to $4 per square foot to hang and finish, and $1 to $3 per square foot for taping and mudding alone. If the walls need insulation first, it adds $1 to $2 per square foot.

To estimate your own garage, measure the area of each wall and the ceiling you plan to cover, add them, and subtract large openings. As an illustration only, 800 square feet of wall and ceiling would be about $1,600 to $3,200 to hang and finish at those rates, before insulation. Ceilings, high walls and a smooth paint-ready finish push the price toward the top of the range.

What changes the price:

•Ceiling height and whether the ceiling is covered

•Insulation, if the garage will be heated

•Finish level: a garage is often left at a basic finish rather than paint-ready

•Electrical work for new outlets or lighting, which must be done by a Licensed Electrical Contractor or under a homeowner's notification to the Electrical Safety Authority

Do I Need a Permit to Finish a Garage?

It depends on the work and your city. Permit rules are set by your municipality: Mississauga, for example, lists garages and interior alterations among projects that need a permit. Call your building department before you start, and say exactly what you plan to do.

Turning a garage into a room you live in is a bigger project than finishing its walls. A garage converted to living space has to meet the code for a living space, including insulation, heating and safe ways out, and your city's zoning rules may affect it. Treat that as a renovation, with a permit, from the start.

Do I Need a Carbon Monoxide Alarm With an Attached Garage?

Yes. Under Ontario's Fire Code, a home with an attached garage needs a carbon monoxide alarm. It goes beside each sleeping area, and since January 1, 2026 on every storey of the home as well. A finished garage wall is no reason to skip it: the alarm is what warns you if exhaust gets in anyway.

What Should a Garage Finishing Quote Include?

Get it in writing, and make sure it spells out:

•The board: regular or Type X, its thickness, and where each goes

•Air sealing of the shared wall and ceiling, and around every opening

•The door: whether the weather-stripping and self-closer are included or checked

•Insulation, if any, and its type

•Finish level for taping and mudding

•Electrical work, and who does it

•Permit: whether one is needed, and who applies for it

Ontario requires a home renovation contract worth more than $50 to be in writing, and recommends a deposit of no more than 10 percent. Before you sign, run the checks in our contractor vetting checklist.

Your Garage Finishing Checklist

1.Decide the use: a finished garage you still park in, or a room you will live in.

2.Call your city about a permit for the work you plan.

3.Measure the walls and ceiling to estimate the drywall.

4.Plan the air sealing of the shared wall, ceiling and every opening.

5.Check the door: weather-stripping, a self-closer, and that it does not open into a bedroom.

6.Test or install a carbon monoxide alarm beside each sleeping area and on every storey.

To find a contractor, compare drywall contractors across Ontario or, for a larger project, general contractors, then put your shortlist side by side with the compare tool.

FAQ

Does the wall between a garage and a house need fire-rated drywall in Ontario?

Not for a garage that serves only the house it is attached to. The 2024 Ontario Building Code treats that garage as part of the house, so no fire separation is required. It does require an air barrier against gas and exhaust fumes, and a tight-fitting, weather-stripped, self-closing door that is not in a bedroom.

How much does it cost to drywall a garage in Ontario?

About $2 to $4 per square foot to hang and finish, plus $1 to $2 per square foot if the walls need insulation first. Measure the walls and ceiling you plan to cover and multiply to estimate your own garage.

Does the door from the garage into the house need to be self-closing?

Yes. Ontario's Building Code requires the door between an attached garage and a home to be tight-fitting, weather-stripped and fitted with a self-closing device, and the doorway cannot be in a room intended for sleeping.

Do I need a permit to finish my garage in Ontario?

It depends on the work and your city. Some cities, such as Mississauga, list garages and interior alterations among projects that need a permit, and converting a garage into living space needs one. Call your building department before you start.

Do I need a carbon monoxide alarm if my garage is attached?

Yes. Ontario's Fire Code requires a carbon monoxide alarm beside each sleeping area in a home with an attached garage, and since January 1, 2026 on every storey as well.

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