If you see water stains or wet drywall in the vicinity of your shower you may have a shower leak. Tracking down the leak may take you some time, but it has to be done before further damage is done to your home. Shower leak repair requires a few basic steps, patience, and a handful of supplies.
Step 1 - Investigate
If you have tile on the inside of your shower enclosure you will want to look for any loose tiles with possible mold around it. Push on the tile to feel if the wall is mushy behind it. If the tile is loose go ahead and pull it off. It is possible you will find wet drywall behind the tile. Often tile grout is corroded or tiles are cracked and water seeps around and under the tile further compromising the surrounding area and allowing water to wick into floor areas. The other issue may be that the shower pan is not properly caulked to the wall.
Step 2 - Remove Damaged Drywall and Shower Pan
Pull off all tile around the pan and any additional loose tile. Cut away damaged drywall and throw it away. Remove the shower pan by unscrewing any screws attaching it to the studs or floor. It should lift out without breaking. You can reinstall the same pan once the area is dry and sealed. You will want to bring in fans and wait several days for the entire area to dry thoroughly.
Step 3 - Match Tile and Buy Greenboard Sheetrock
While your area is drying you can shop for matching tile if you were unable to salvage the tile you removed. If your tile is no longer available this may be a good time to get creative and purchase a tile that will form a contrasting or decorative pattern. You may also want a new shower pan at this time as well, but that is all dependent on the condition of your old one and personal preference.
Step 4 - Install Greenboard Sheetrock
Cut the sheetrock to size to snug up to the existing sheetrock. Nail it to the studs and tape and float the seams.
Step 5 - Install Shower Pan
If the sub-floor is completely dry you may want to paint a sealant and mold-killing paint on the floor before re-installing your old or new shower pan. Re-install the pan with the same attaching hardware as before.
Step 6 - Replace Tile
Draw lines on the sheetrock to indicate the pattern and spacing of the new tile. Using tile adhesive, place one row at a time beginning at the bottom, allowing each row to set before adding additional rows. Grout the tile.
Step 7 - Caulk the Shower Pan
Using the appropriate bathroom sealing caulk run a bead of caulk around the shower pan making sure that it is well sealed.