Wash the surface of the wall behind and around the vanity, using a cleansing mixture created with approximately 1 tsp. of mild liquid soap mixed thoroughly in a bucket containing a gallon of water. Use a sponge to clean the wall, removing any dirt or soap scum. Rinse after washing with clean water, and then pat the wall dry with a piece of clean cloth.
Remove any caulk present surrounding the vanity against the wall by cutting it away with a utility knife. Clean any residue left from the caulk with a piece of cloth dipped in isopropyl alcohol.
Place a strip of masking tape along the vanity edge, and put a drop cloth along the base of the wall where you need to apply the sealer.
Select a waterproofing topcoat that's compatible with the paint type used on your wall. For oil-based or solvent-based paints, you need an oil-based or solvent-based topcoat. For acrylic-based or latex-based paints, you can use an acrylic-based or latex-based topcoat, as well as an oil-based or solvent-based solution. Use a clear topcoat to preserve the present color of your wall.
Dilute the waterproofing topcoat according to the manufacturer's instructions, if necessary. Apply the topcoat to the wall that the vanity rests on. Use a paintbrush to apply the topcoat along the edges of the surface, brushing on a strip of the coating approximately 3 inches wide. Cover the rest of the wall, using a paint roller and applying the topcoat in overlapping rows. Begin with a 2-inch overlap of the brushed edges. Wait for the topcoat to dry. Check the topcoat manufacturer's instructions for drying times. Apply two to three more coats, allowing each coat to dry before you move on to the next. This will allow you to build up a sufficiently waterproof layer.
Remove the masking tape and then place a bead of caulk around the edge of the vanity where it meets the wall. Smooth the caulk along its length with a wet fingertip. The caulk prevents water splashed onto the wall from dripping behind the vanity. Turn on the water supply to the vanity after you've applied the caulk.
Things You Will Need
- Mild liquid soap
- Utility knife
- Masking tape
- Drop cloth
- Waterproofing topcoat
- Paint roller
- Remove the vanity if possible to apply the topcoat to the wall along the vanity rear for a more complete coverage.