Steps to Prepare Walls After Skim Coating With Joint Compound

Sanding

• Sanding is essential between and over skim-coat layers. Sanding prepares the wall to accept the next coat of paint or joint compound, and it further smooths the material that’s already in place. Attach a sheet of 120- to 150-grit sandpaper to the pad on a pole sander. This tool helps reach the top of the wall without using a ladder, making reaching across or down walls much easier. You don't need to apply much pressure when sanding. A light sanding is all the wall needs. For walls that are already smooth, use a damp, dense sponge or a "wet-sanding" sponge for sanding. Make sure the sponge is well-wrung so it doesn’t leave walls too wet.

Cleanup

• Sponge sanding takes care of itself where cleanup is concerned. When using sandpaper, however, the walls get coated with a film of fine particles from the joint compound and sandpaper medium. Vacuum the walls thoroughly, removing all particles possible. Then, go over the entire wall with a damp sponge, which removes the rest of the fines left behind after vacuuming. Allow the wall to dry completely before painting.

Primer

• Choose a good quality primer when preparing a wall for paint. Primers give the top coat of paint a better surface with which to bond than bare walls. If any stains are bleeding through the drywall and skim coats, select a primer that has stain-blocking properties. Water-based primers are made for use with latex finishes. Oil-based primers work with oil-based paints. You may want to consider all-prime formulas, which work well with either type of paint.

Sizing

• Sizing protects drywall and joint compound from the water used when hanging wallpaper. It also provides a strong surface onto which wallpaper grips in much the same way as paint does when applied over primer. You can prime the walls, then add sizing over the primer, or select a primer that already has sizing mixed in it. The latter method saves a step. If you can't find primer with sizing, or prefer to add a sizing coat yourself, the product is readily available at home centers, wallpaper retailers and hardware stores.