Apply several coats of moisture-resistant drywall primer (also called wallboard primer or primer sealer). The product should be both moisture- and mold-resistant. The goal is to create a seal that will keep water from compromising the integrity of the paper facing. Keep in mind that damage to the wallboard will allow water to get under the primer, which may then peel away.
Cover the drywall primer with semi- or high-gloss paint. Both these types of paint work well in bathrooms and damp basements. As with primer, water can cause the paint to peel and blister if it works its way underneath the layers of paint, so avoid damaging the wallboard.
Seal all gaps around the wallboard with silicone caulk. Place a tube of caulk into the caulk gun. Snip the tip off the nozzle with scissors. Squeeze the trigger to advance the caulk. Fill all gaps completely. This will prevent water from entering the area behind the wallboard.
Things You Will Need
- Drywall primer/sealer
- Semi- or high-gloss paint
- Caulk gun
- Install new water-resistant wallboard, if you have the option. For example, wallboard that has green or blue paper facing has a special chemical treatment that helps it resist occasional splashes of water. But blue and green wallboard are not suitable for areas that encounter constant moisture and water vapor, such as in shower or bath areas. Another alternative is paperless wallboard, which has fiberglass mesh instead of a paper facing. Paperless wallboard is more water-resistant than blue or green wallboard but has a slightly rough texture that requires an extra skim coat of joint compound to look smooth. Finally, backer board (also known as concrete board) is waterproof and is suitable as a substrate for tile, but it is expensive, heavy and has an extremely rough surface.