The bathroom is the most moisture-exposed room in the home. Pipes run water in and out of the room from sinks, showers and commodes, plus there is steam from the shower that lingers in the air long after bathing is finished. With the shower being the place where water is sprayed out, only to be caught by a small tub or shallow area at the bottom, it is a good idea to make sure that it is waterproof to prevent moisture damage to the walls. Shower enclosures have seams that should be caulked to keep water out.
Nail backer board, such as a cement-based or green board, to the walls before installing a shower enclosure. Use this type of board instead of drywall, because drywall will be damaged by exposure to moisture. Green board is only water-resistant, but is usually enough if the shower enclosure is fibreglass, porcelain or some other solid material. Cement-based boards are waterproof and will not allow mould growth. If there is a leak around faucets or a crack in the shower, this is what you want on the walls behind the enclosure.
Apply caulk along the seams of the shower enclosure. Load a cartridge of waterproof silicone caulk into your caulk gun. Cut off the tip of the cartridge at an angle, using your utility knife. Press the trigger on the caulk gun to apply a caulk bead to all seams. Apply caulk around fixtures and the outside of the shower where the enclosure meets the floor or wall.
Run your finger along the bead of caulk to smooth it down and seal it to either side of the seams or openings.
Hang a curtain rod and liner to keep water from ending up on the floor when the shower is being used.
Try to apply caulking continuously to prevent gaps or bubbles.