Where fire separation is required
Attached garages typically need gypsum separation on walls and ceilings shared with living space — commonly 1/2 inch Type X on garage side of house walls and ceiling under habitable rooms. Local code may require 5/8 inch on certain boundaries or fire-rated assemblies.
Check your jurisdiction — IRC and local amendments vary on garage-to-bedroom walls, breezeways, and detached garages with living space above. Permits often trigger inspection of labeled Type X board.
- House wall facing garage: Type X gypsum
- Ceiling under finished room above garage: often 5/8 Type X
- Doors to house: self-closing, solid wood or rated
- Penetrations: fire caulk at boxes and pipes per code
Type X vs regular drywall
Type X board has glass fibers and core additives for fire resistance — it is heavier and slightly harder to snap. It is not a substitute for a full rated assembly if code calls for a specific UL design.
Use Type X only where required — it costs more. Standard 1/2 inch is fine on exterior garage walls not shared with the house.
Calculating garage separation sheets
Measure only separating surfaces — not all four garage walls if two are exterior cladding. A 22×24 ft two-car garage sharing one 24-ft house wall and 22-ft ceiling band under a bedroom might need 15–20 sheets of Type X depending on height and door openings.
Enter separating walls and ceiling as separate calculator rooms in our drywall calculator. Label Type X on your order — suppliers stock it separately from standard board.