Drywall Repair
Damaged drywall can be repaired relatively easily. You can use cement backerboard in place of drywall for walls containing tile. Soggy drywall can then be removed and the hole measured for a patch. The backerboard or water-resistant drywall can then be cut to size, attached to the existing wall with galvanized screws and covered with a layer of mastic or drywall mud. Once dry, the tile or tub surround can be replaced.
Plumbing Repair
Leaky plumbing is often the cause of a soggy shower wall. There should be an access point to the shower plumbing on the other side of the wall. Leaky connectors should be tightened or replaced, and in extreme cases the seal between the pipes may need to be repaired. With the water supply turned off, unscrew the connector, and apply a piece of plumber's tape to the threads. Any cracked pipes or stubborn connectors may require the assistance of a professional plumber.
Tile Repair
Tile can be removed piece by piece with a chisel and hammer, eliminating the need to remove the entire tub surround. Once the affected area has been completely revealed, patch the drywall and install the replacement tiles. Tile is typically attached to drywall or backerboard with a layer of grout, which is then applied to the spaces between each tile. The surface of the tile is then cleaned with a nonabrasive cleanser to remove any traces of grout.
Surround Repair
Fiberglass or acrylic tub surrounds are inexpensive; a usable model can likely be found for around $50 as of July 2011. Installation requires a waterproof adhesive, waterproof caulking, a measuring tape and a utility knife. Remove each fixture trim piece, and use the back of the box as a template to mark out the holes for the faucet and handles. The pieces are then cut to size and glued to the wall. Once the glue has dried, caulk the seams and edges to create a watertight seal.