How to Wonderboard Around a Bathtub

Remove existing drywall from the walls. Check for moisture damage or mold. Contact a professional if mold is spotted. Staple 4-mil plastic over the studs as a moisture barrier behind the Wonderboard. Measure the installation area and add 10% for waste. Purchase 1/2-inch Wonderboard for tub walls.

Measure the first course at 3 feet off the tub surface, mark this point at several points across the studs, snap a chalk line connecting these points. With the help of an assistant, hoist the first piece of Wonderboard up to the wall and line the piece up with the horizontal 3-foot line. Nail in the first piece with 1 1/2-inch galvanized roofing nails, nailing every 6 inches at each stud. Stagger Wonderboard joints with those of adjacent rows as you continue. Install all of the full pieces.

Measure the dimensions to cut the Wonderboard. Cut the first piece using a utility knife and straight edge. Hold the straight edge at the proper measurement, score the line with the knife, snap the Wonderboard in the opposite direction of the cut. Cut excess mesh from behind the folded piece. Cut round cuts, such as around plumbing fixtures, with a 4-inch grinder or Dremel tool. Wear a dust mask, leather gloves and eye protection as you are cutting.

Apply polymer-modified thinset at all joints and corners. Embed 2-inch alkalai-resistant fiberglass mesh tape over joints and corners. Smooth the tape into the polymer-modified thinset. Apply water-resistant caulking at the Wonderboard-tub seam. Allow 24 hours before installing tile.