Tile Repair and Maintenance
Cracked or broken ceramic tiles that are set over drywall are difficult to replace properly. This is because the drywall is usually also damaged and may need to be repaired first.
Whenever you install new ceramic tile be sure to save some tiles in case you ever need to replace a few. It's almost impossible to buy a new tile to match your existing one. Even if you can get the exact same brand and color, the color may be a little different than the ones produced a few years ago.
Replacing Broken Tile
If a single tile has been cracked or chipped, you can usually repair it without replacing the underlayment.
To replace one tile, first dig out the grout around it. Do this with a special tool called a grout saw. A utility knife works well too. For a group of tiles, dig out around the section of tiles you're replacing.
Shatter the broken tile into small pieces by hitting it with a hammer and a nail set. Be sure to wear safety glasses because pieces may go flying.
Pry out the pieces carefully and scrape off the grout and adhesive with a chisel or putty knife. If drywall is under your tile, be careful not to dig into it. Clean out all the debris and get the surface as clean as possible.
If you're replacing a group of tiles, you should try to set them with the same type of adhesive as the original tiles. For one tile you can just use a silicone adhesive. The trick is to put the right amount of adhesive on so the new tile will sit level with the original ones.
Press the tile into place and clean up any adhesive that oozes through the joints. If you're replacing a tile on a wall, tape it into place until it dries. Let the adhesive set up for the recommended amount of time.
Find a grout to match that of the existing grout color. If you're only grouting a small area you can pick up a little container of premixed grout. Work the grout into the joints with a grout float. In a small area you can just use your finger.
Wipe off the excess grout and use a sponge to shape the joints and remove the grout left on the tile. This might be a good time to
regrout all of the tile, especially if you're in a shower or other high-moisture area. This will also make your repair job less noticeable.
Regrouting and Sealing Tiles
Glazed tiles have hard, sealed surfaces. Grout is porous and absorbs water, so it can get moldy. It can even let water pass through into the wall.
For these reasons tile should be sealed periodically to prevent any moisture penetration, especially in areas that are exposed to water. And grout should be replaced if it gets moldy.
First clean the grout joints, then apply a silicone or water-based grout sealer to the joints. As long as the tile is glazed it's ok if you get some sealer on the tile surface, but you'll need to wipe it off before it dries.
In wet areas, if grout lines have cracked there's a good chance that water has seeped through to the underlayment. And if your underlayment is drywall, there's probably some damage and it may need replacing.
Cracks in dry areas probably mean settling of the underlayment or shifting with temperature changes.
If cracks are small and clean, you can just press in new grout with your fingers. If cracks are large and have dirt or mildew in them, first scrape out the old grout with a grout saw or utility knife.
Vacuum or brush out any dust or dirt from the joints. Then use a cleaner to remove any dirt, oil or soap scum. Allow it to dry.
Use a mildew-resistant grout with a latex additive to grout the joints. Then clean the tiles off with a sponge and let them dry. (See Grouting Tile)