How to Fix Damaged Walls of Plaster Board
Reasons for Small Holes
Common fasteners do not perform too well on plaster board, and the results are often holes which are unattractive. It's always best to remove anchors properly. Standard plastic anchors generally do not expand much. Insert a tight fitting screw about one quarter of an inch in and pull back to remove. If you reach resistance, you may have a toggler type plastic anchor. It must be drilled out like a molly type below. Toggle bolts have a butterfly back that falls off when unscrewed. Molly type fasteners are metal, have a shoulder against the wall with two small indentations, and expand behind the wall. Use a drill bit just larger than the screw to cut through the molly so the back comes loose, and by reversing the drill, it can fall into the wall cavity.
Depending on the size of the hole, most can be filled with with patching plaster or a better grade of lightweight non-shrinking, ready mixed spackling compound. If necessary, you may apply self-adhesive fiberglass mesh wallboard tape, and finish with coats of compound.
Repairing Open Joints
When the original tape comes loose, don't try to salvage it. Remove it, sand away loose sections and rough edges, apply a new coat of joint compound, and embed new tape into it. Finish with two or more coats of compound, feathering the edges and sanding smooth.
Repairing Larger Holes
This method uses wallboard that is the same thickness as the wall. Cut out a rectangular section including the hole. Use a drywall or key hole saw. Cut a scrap piece of plaster-board to fill the hole of the wall, making it about a quarter of an inch shorter and narrower. This will allow a 1/8" fill border on all sides. Using either scraps of 1" by 3" lumber or furring strips cut a few inches longer than the hole, insert them in the wall so they can be screwed in from the front and edges with drywall screws, and act as a backstop for the new section. Insert the patch, screw it up with drywall screws, and finish with tape and a few coats of compound as above. Sand lightly and paint.