Why Garages Need Special Drywall
Garages store flammable stuff. Gasoline, paint thinner, propane, oily rags. They're also where cars start, which involves combustion. If a fire starts in the garage, the drywall's job is to slow that fire from reaching the living space.
Building codes require fire separation between attached garages and living areas. The specifics vary by jurisdiction, but the concept is universal: give occupants time to escape and give the fire department time to respond before fire spreads through the house.
Detached garages don't have these requirements because there's no shared wall with living space. But attached garages, even if they're just under a bedroom or share a wall with a hallway, need fire-rated assembly.
Type X Drywall Explained
Type X is a classification, not a brand. It means the drywall meets specific fire resistance standards. Type X achieves this through glass fiber reinforcement in the gypsum core that holds together longer under heat.
Standard Type X is 5/8 inch thick and provides one-hour fire resistance when installed correctly. This is what most residential codes require for garage-to-house separation.
Type X looks like regular drywall but you can identify it by the edge stamp or the yellow coloring some manufacturers use. Always check that you're getting Type X when required. Regular 5/8-inch drywall is not fire-rated just because it's thick.
For some applications, especially multi-family or commercial, you might need Type C, which is even more fire resistant. But for typical residential garage-to-house separation, Type X is the standard.
Where Fire-Rated Drywall Goes
Not every surface in a garage needs fire-rated drywall. Just the surfaces that separate the garage from living space.
The common wall between garage and house: Fire-rated required. This is usually the most obvious one.
The ceiling if there's living space above: Fire-rated required. If the garage is under a bedroom or bonus room, that ceiling needs protection.
Walls adjacent to unoccupied attic: May or may not require fire rating depending on your jurisdiction and how the attic connects to the rest of the house.
Exterior garage walls: No fire rating required. These are just between the garage and outside.
Garage-to-garage walls in townhomes: Typically require fire rating as separation between dwelling units.
Check your local codes. The specifics vary. What I've described covers most cases, but your jurisdiction might have additional requirements or exceptions.
Installation Requirements
Fire-rated drywall must be installed to maintain its rating. Gaps, holes, and poor workmanship can compromise the fire barrier.
No Gaps
Drywall should fit tight to framing with no gaps. Where sheets meet, seams should be snug. The fire-rated ceiling should meet the fire-rated wall with no openings.
This is stricter than regular drywall where 1/8-inch gaps are acceptable. For fire assemblies, minimize any gaps that could let fire through.
All Joints Taped
Every seam must be taped and mudded. Untaped joints are breaks in the fire barrier. This includes seams that might normally be left untaped in non-fire-rated work.
Penetrations Sealed
Anything that penetrates the fire-rated assembly needs proper sealing. Electrical boxes, plumbing, dryer vents, all create holes in the barrier.
Electrical boxes should be fire-rated types or surrounded by fire caulk. Pipes get fire-stopped with rated sealant. Larger penetrations might need fire-rated collars or dampers.
The passage door between garage and house must be fire-rated. Typically 20-minute rated minimum, solid core. It must be self-closing, which means you need a door closer or self-closing hinges. And the threshold must be tight with no gaps underneath.
Common Garage Drywall Mistakes
Things I've seen done wrong:
Using regular drywall. The thickness alone doesn't make it fire-rated. Type X has special composition. Using regular 5/8-inch fails the fire separation requirement.
Stopping at the car. People sometimes drywall only the back wall and ceiling where they see it most. But fire rating requires coverage of the entire shared assembly.
Unsealed penetrations. Every hole needs attention. That wire running through to the house? Fire caulk around it. The exhaust vent? Fire damper where it penetrates.
No separation at attic. If the garage ceiling has attic access, and the attic connects to the house attic, fire can travel that path. The attic needs separation too.
Wrong door or no closer. The door from garage to house is part of the fire assembly. It has to be fire-rated, and it has to close automatically. A regular hollow-core door won't stop fire.
Detached Garage Considerations
Detached garages typically have no fire-rating requirements because they don't share structure with living space. You can drywall them with regular materials or not drywall them at all.
Reasons to drywall anyway: Insulation value if you heat or cool the garage. Cleaner look. Protection for the framing. Easier to hang stuff on walls.
If you do drywall a detached garage, regular 1/2-inch is fine. You don't need Type X unless you want it for impact resistance or have some other reason.
My detached shed has no drywall. It's just storage. My friend's detached garage, which he uses as a workshop, has regular drywall over insulation because he heats it in winter. Both approaches are fine for detached structures.