Building code requires 5/8-inch-thick fire-rated drywall, known as Type X, on the garage ceiling and walls when an addition is put on above. (The wall shared by the garage and the house should already have it.) "If the framing were left exposed, it would be damaged too rapidly in a fire," says Tiplady. Penetrations in the drywall, for electrical conduit and the like, must be sealed tightly.
Shown: With careful planning, homeowners Geoff Allen and Michelle Forcier gained space above their attached one-car garage for their young daughter's cheery bedroom.