How to Seal a Ceramic Tile Shower

Written by b. ellen von oostenburg
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The constant enemy that can undermine the installation of a tile shower is water. You build a tile shower in the first place to experience the pleasure of hot water cascading down over your body. But while this is happening water will naturally penetrate any unsealed spots in the overall construction of your tile shower. There are many aspects to sealing a shower properly. If all are attended to, you can shower with peace of mind that your tile construction is secure.

Skill level:

Things you need

  • Waterproof membrane
  • Mastic or thinset mortar
  • Trowel
  • Tile
  • Grout
  • Grout sealer
  • Tub & tile silicone caulk
  • Caulk gun

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  1. 1

    Add a waterproof membrane behind the backing board that the tiles will be glued to. Even if water penetrates and gets behind the board, the membrane will channel the water back down into the shower pan where it can drain away. Make sure when installing the waterproof membrane that the bottom edge laps over the top lip of the shower pan. Don't run it underneath it. Water might get trapped under the pan where it can't drain away and over time might start rotting the wood floor and beams. Use cement board for the backing board of your tile shower. Even if cement board gets wet it doesn't disintegrate, as regular wallboard or green board might over time.

  2. 2

    Apply mastic or thinset mortar to the backer board of the shower with a trowel. Rake grooves through it with the notched edge of the trowel. Set the tiles into the mastic or mortar; press and then wiggle the tiles to seat them. This insures a tight bond and seals the back of the tile into the mortar or mastic so if water does penetrate there are no voids in back of the tile where water can repeatedly collect. Allow the mastic or mortar to dry.

  3. 3

    Mix up grout and work it into the spaces between the tiles. Grout seals the unglazed edges of the tiles and keeps water from penetrating to the backing board. Allow the grout to dry for at least 72 hours before applying grout sealer.

    Grout sealer forms a waterproof film that resists water and oil. Grout sealer can be applied with a brush, roller ball applicator or spray bottle. Grout sealer must be wiped off of any glazed surfaces. Do not get grout sealer on unglazed tile surfaces. It will be absorbed and may leave a residue stain that can't be removed from the surface of the tile.

  4. 4

    Load a tube of tub and tile sealing silicone caulk into a caulk gun and run a bead of caulk down each inside corner of the shower stall. Also run a bead along the bottom of the shower stall where the walls meet the shower floor. If installing a shower door, run a bead of caulk down each side of the tiled doorway opening, where the metal tracks of the door will be screwed to the face of the tiles.

Tips and warnings

  • To run a smooth, even, unbroken bead of caulk, take two strips of masking tape and run them down the tile walls parallel with the corners. The inside edge of each strip of tape should be about 1/8 inch away from the corner on both adjoining walls. Run a bead of caulk down the corner from top to bottom. Dip your index finger in water and pull the tip of your finger down over the bead of caulk from top to bottom. Carefully pull the strips of tape away from the two walls. Use this method for the bead of caulk where the walls meet the floor of the shower.

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