What Fire Separation Is Required Between an Attached Garage and a House?

Attached garages are treated as a separate fire compartment from the dwelling. Shared walls and ceilings between the garage and living space require a fire-resistance rating under OBC Part 9. The exact rating depends on whether the garage is attached beside the house or built into it.

Fire-rated construction typically means gypsum board assemblies, taping, and continuity at joints and penetrations. Removing drywall during a renovation without replacing a rated assembly is a common reason for inspection failure.

Doors between the garage and house must be self-closing and meet fire-protection requirements. Labeled fire doors or solid wood/steel doors of prescribed thickness are typical solutions. Hollow-core doors are not acceptable in this location.

Self-closing devices (spring hinges or closers) must keep the door closed. Propping the door open defeats the separation. Weather stripping and tight-fitting frames also reduce air and vapour movement between the garage and dwelling.

The requirement exists because vehicles, fuels, and ignition sources in garages present elevated fire and carbon monoxide risk. Separation gives occupants more time to escape and limits fire spread into sleeping and living areas. CO alarms are also required near sleeping areas when an attached garage is present.

Detached garages generally do not need the same wall/ceiling separation from the house because they are not attached — but breezeways, shared walls, and conversions to living space change the rules. Converting a garage into a bedroom or living room requires permits, structural upgrades, egress, insulation, and often removal of garage-specific fire separation in favour of dwelling construction.

Common renovation mistakes include drywall-only walls without the required rating, propped-open self-closing doors, cutting pet doors into fire-separation doors, and unsealed pipe or duct penetrations through rated assemblies.