What fire-rated drywall is required between an attached garage and living space under Ontario Building Code?

Under the Ontario Building Code, the wall and ceiling between an attached garage and the living space must achieve a minimum 45-minute fire resistance rating, which requires 5/8-inch Type X drywall on the garage side with all joints fully taped and finished. This is one of the most critical fire safety requirements in residential construction, and it applies to every home in the GTA with an attached garage — whether it's a new build in Vaughan, a 1970s bungalow in Scarborough, or a semi-detached in the Annex.

Type X drywall is specifically engineered for fire resistance. It contains glass fibres within the gypsum core that hold the board together as it's exposed to fire, buying time for occupants to evacuate and for fire crews to respond. A single layer of 5/8-inch Type X drywall on wood framing provides a 45-minute fire resistance rating when properly installed. Standard 1/2-inch regular drywall does not meet this requirement and cannot be substituted. In the GTA, Type X 5/8-inch drywall costs $20–$28 per 4x8 sheet, compared to $14–$20 for regular 1/2-inch — a modest premium for life-safety protection.

The fire separation must be continuous and complete. This means every gap, penetration, and joint must be properly sealed. All joints in the Type X drywall must be taped and finished with joint compound — you cannot leave unfinished joints in the garage even though it's not a living space, because gaps in the fire separation defeat its purpose. Electrical boxes, plumbing penetrations, and any other openings through the fire-rated wall must be sealed with fire-rated caulking or approved fire stop materials. HVAC ducts passing through the garage-to-house wall require fire dampers.

Key Details Homeowners Often Miss

The fire separation includes the ceiling of the garage if there is living space above. If you have a bedroom, bonus room, or home office above your garage, the entire garage ceiling must also have 5/8-inch Type X drywall. This is common in many GTA two-storey homes built from the 1980s onward, particularly across Mississauga, Brampton, Markham, and Richmond Hill where two-storey homes with living space over garages are the dominant housing type.

The door between the garage and living space is also part of the fire separation assembly. It must be a solid-core wood door or a fire-rated door (minimum 45 minutes), equipped with a self-closing device (spring hinges or a door closer). Hollow-core interior doors do not meet this requirement. The door must also have weather-stripping to prevent carbon monoxide and exhaust fumes from entering the living space.

One common violation that GTA building inspectors flag is installing the Type X drywall on the house side instead of the garage side of the shared wall. The fire-rated drywall must face the garage because that's where a vehicle fire would originate. On the house side of the same wall, standard 1/2-inch drywall is acceptable.

Another frequent issue involves garage conversions. If you're converting your garage to living space — a popular project in Toronto given the city's housing costs — the fire separation requirements change because the garage is no longer a garage. However, this type of conversion requires a building permit, and the City of Toronto inspector will verify that all new wall assemblies meet current code requirements for insulation (R-24 above grade), vapour barrier, and fire separation from adjacent units in semi-detached or row house configurations.

For a typical two-car attached garage in the GTA, installing fire-rated Type X drywall on the walls and ceiling runs approximately $3,500–$6,000 including materials, labour, taping, and finishing. This covers roughly 600–900 square feet of fire-rated assembly at $3.50–$6.00 per square foot. It's a worthwhile investment in safety, and it's not optional — building inspectors will flag non-compliant fire separations during permitted renovations, home inspections during sales, and insurance assessments.

If you're unsure whether your garage fire separation meets current Ontario Building Code requirements — especially in older GTA homes where the original drywall may have been damaged, removed, or improperly replaced — a professional drywall contractor can assess the situation and bring it up to code. Browse drywall professionals in your area through the Toronto Construction Network directory.