Hanging ceiling drywall is a straightforward but cumbersome project due to the unwieldy size and weight of the panels. When a layer of rigid foam insulation covers the ceiling joists, the drywall installer has the additional task of determining the locations of the joists because they’re not visible. It’s important to make a layout plan before starting to ensure that the drywall panel seams do not meet on the same joists as the foam board seams.
Use a stud finder to locate ceiling joists and mark the center of each joist with a chalk line.
Draw a to-scale layout of the ceiling joists on graph paper and include the locations of the foam board seams. Standard foam board comes in 4-foot-by-8-foot sheets so the seams should meet, or “break,” on standard spaced, 16-inch or 24-inch joists.
Configure your drywall panel layout so the seams do not correspond with the foam board seams. Drywall panels should run perpendicular to the joists.
Raise drywall panels into position with a drywall lift. Follow your layout and make sure the panels fit tightly together before screwing.
Fit a cordless screwdriver with a drywall bit. A drywall bit has a small shoulder that reduces the risk of inserting the drywall screw too deeply, which can tear the protective drywall paper.
Select drywall screws long enough to penetrate the joist by 1 inch. For example, if you’re installing 1/2-inch drywall and the rigid foam board is 1/2 inch thick, use 2-inch drywall screws. If the foam board is 1 inch thick, use 2.5-inch drywall screws.
Check building codes to see if your local building authority requires a specific screw pattern. If not, insert drywall screws at the rate of every 6 inches on seams and every 8 inches in the plane of the panel.
Cut drywall panels only when fitting a too-long panel at the end of the ceiling. A simple way to cut a panel is to score the surface paper on the top side about 1/8 inch deep, turn the panel on its side and bump the back firmly behind the scored line. The panel will break along the line and you can then cut the remaining paper backing with the utility knife.