Drywall Preparation

Mudding

• Joint compound, or mud, is made of the same material that is in the center of the drywall, mixed with water to create a paste. Joints between sheets of drywall are covered with mud, which is pressed into the joint and spread over the surface of the drywall around it. When mudding and taping are done properly, the joints are completely invisible after the wall has been painted.

Taping

• Drywall tape is used in conjunction with mudding to cover the joints between sheets of drywall. After spreading mud over a joint, tape is laid on top of the mud and pressed into it with the flat side of a drywall knife. More mud is then spread on top of the tape and feathered out onto the surface of the drywall, creating a joint that is a foot or more wide. The width of this joint allows the drywaller to create a gradual transition from the mud to the drywall so that it doesn't show after the wall is painted.

Sanding

• Sanding of mud is done with fine sandpaper mounted on a sanding block. For large areas, the sanding block is attached to a pole, allowing the worker to sand in large, even arcs and create a smooth surface. The purpose of sanding is to remove unevenness in the surface of the mud, and to feather down the edges where the mud meets the surface of the drywall. It is important to put enough mud on top of the drywall tape so that the tape remains unexposed after sanding.

Priming

• Once the sanding is finished and the surface of the wall is completely smooth, the entire surface is painted with primer, using a roller for the main sections and a brush for the corners and edges. Primer creates a binding surface that helps finish paint adhere more solidly to the drywall. Going over the entire wall with a broom, rag or vacuum before priming helps to remove drywall dust and create a cleaner surface for application of the primer.