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How to Waterproof Ceilings

Nicole Brown

Water damage can weaken the drywall that covers ceiling studs, which can lead to costly and extensive repairs. Damp ceiling drywall can bow, crack and become discolored, detracting from the visual appearance of your living space. It can also swell, causing cracks along the top of adjacent walls. Waterproofing a ceiling to prevent damage is a relatively straightforward task -- in most cases, you can complete it over the span of a weekend.

Step 1

Unroll waterproof membrane over the ceiling joists in the attic. Press the membrane over the joists and against the subfloor. Overlap membrane sections to prevent moisture from penetrating the seams.

Step 2

Staple the membrane to the sides of the joists and the subfloor with an electric stapler. Apply waterproof tape to the seams.Trim the membrane as needed with a utility knife.

Step 3

Apply polyurethane sealant to the interior surface of the ceiling with a 3-inch paintbrush. Allow the polyurethane to dry for at least eight hours. Apply a second coat to fully seal the ceiling drywall.