How to Skim-Coat Drywall After Wallpaper

Prepare the wall by removing any nails or other objects. Patch any nail holes, dimples, nicks or other serious irregularities with joint compound applied with a wide --- approximately 6-inch --- drywall taping knife. Push the compound into any divots, and smooth it with the knife. Let the patches dry. Sand the entire wall with a power sander and fine --- at least 120-grit --- sandpaper until all paper remnants and irregularities are smoothed out. Put a plastic or other protective covering on the floor and any furniture before sanding.

Wipe the wall with a damp cloth or wet sponge to remove all the dust. Tape off any windows, doors, electrical outlets or other openings with painter's tape, and cover the floor with a drop cloth. Hang plastic over any doors to other parts of the house if you are doing a big project to prevent dust and debris from filtering outside the working room.

Use either a broad --- 10- or 12-inch --- taping knife or a flat trowel, a tool with a flat steel bottom roughly 4 by 10 inches with a straight edge and a notched edge. Mix drywall compound, or buy a ready-mixed version in a large container, which is easier. Pick up a blob of compound with either tool and put it on the wall, spread it with the knife or trowel and use a straightedge to smooth it. Work in areas of approximately 4 feet square at a time, starting at the ceiling and working down.

Let that coat dry, and sand the wall with 150-grit sandpaper. Check for any missed places or uneven spots. Wipe the wall clean of dust, apply a second coat just as you applied the first and let it dry. Sand that coat and put on a third coat if necessary to get the surface smooth and even. Apply thin coats; two or three thin coats will produce a better result than one thick coat. Wipe the dust from walls, and remove any tape or coverings.