What drywall is required between an attached garage and the house?

At least 1/2-inch gypsum board on the garage side, and 5/8-inch Type X gypsum board on the ceiling when there are habitable rooms above the garage (IRC R302.6).

The garage must be separated from the residence with not less than 1/2-inch gypsum board applied to the garage side of the common walls.

Where habitable rooms are located above the garage, the ceiling separating the garage from that space must be not less than 5/8-inch Type X gypsum board. The structure that supports that separating assembly is protected with not less than 1/2-inch gypsum board.

This separation is a prescriptive material requirement under Table R302.6; it does not by itself establish a specific fire-resistance rating.