Gypsum board can be applied over wood or metal framing or furring. It can be applied to masonry and concrete surfaces, either directly or to wood or metal furring strips. When applying board directly to masonry or concrete surfaces, smooth or fill in any irregularities to ensure proper attachment and an acceptable final finished surface. Furring properly attached to interior sides of exterior walls provides flat surfaces for standard fastener application as well and sufficient separation from substrates to overcome dampness in exterior walls. Do not allow gypsum board to directly contact surfaces, such as concrete or soil, with potentially high moisture contents. Most common in residential construction is the gypsum wallboard system¹in which the joints between the panels and internal corners are reinforced with tape and covered with joint compound to create a surface suitable for final decoration. External corners are normally reinforced with either a metal or plastic corner bead which in turn is covered with joint compound. Exposed edges are covered with metal or plastic trim. The result is a smooth, unbroken surface ready for final decoration of paint, textures, wallpaper tile, paneling, or other materials