Exterior Gypsum Board is primarily used in ceiling applications of covered/sheltered areas as a finish surface or backer for siding, wood, or vinyl. It is also a popular material for exterior soffits. The inside of the sheets are a special formulated and gypsum core with chemically enhanced water repellent paper face. It is commonly utilized in breezeways, exterior soffits, carports, and porches. It can be installed on wood or metal framing or furring. Final in place costs is often less than most plywood, laminated fiberboard or plaster. Exterior gypsum board can be scored with a utility knife and snapped/broken into pieces similar to drywall. Joints can be finished with a special bonding/hardening “setting-type’ joint compound for a flush, smooth, finish. The joints may also be covered with a basic wood batten grid system as well. It is also commonly sold in a fire code type which can be implemented in many 1 and 2 hour fire resistant design. The sheets are either 1/2″ or 5/8″ thick and come in 4×8 or 4×12 stock sizes. The panels should not be directly exposed to wind, snow, or rain and should not be spanned over framing spacing exceeding 24” on center. Control joints are often required for isolation of structural movement in which case a zinc control joint or H-Molding is often utilized.
Edges can come eased or tapered. Sheets weights are very similar to drywall. Fasteners styles and sizes should be very similar to interior drywall requirements.