Impact Crack

• The most common cause of a cracked tile is impact. Something has fallen on the shower floor, or heavy impact has been made with a shower wall. Impact-cracked tiles are the easiest to replace; you know the cause of the break and they are most likely on the floor of the shower. If you remove and replace the cracked tile quickly enough, no damage will be done to the substrate from water seepage. If the broken tile has been allowed to sit, though, water may have damaged the underlayment. If this damage is widespread, the installation, not just the tile, will need to be replaced.
  
  

Isolated or Widespread

• Before determining whether you can replace a broken tile, it helps to determine the cause of the crack. If something was dropped on the shower floor, cracking a tile, this is an isolated incident and you can easily remove and repair the tile. If multiple tiles are cracking across the shower, the problem may be too widespread; replacing tiles will only lead to more replacements down the road. Try to determine the cause of the breaks, such as tiles too large for the slope of the drain on the floor, lack of grout joints, or simply poor quality product. Isolated or few broken tiles should be replaced; multiple cracked tiles may require a new installation.
  
  

What's Behind the Tiles

• Shower tiles are subject to moisture on a daily basis. If water has gotten behind the tiles or worked its way through some cracked or broken tiles, there may be more widespread damage, particularly if the shower is old and the grout is also cracked.
  
  Tap against the tiles gently and listen to the sound. Compare the sounds produced throughout the area; a hollow or deep sound may mean the backer board behind the tiles is compromised and the tile installation cannot be saved by replacing the broken tiles. If the backer board is sound, you can most likely replace the tiles.
  
  

When to Repair and When to Replace

• It can be difficult to remove a cracked tile from a wall tile installation without removing or compromising the backing behind it. If a single tile has cracked in a shower installation, and the crack is clean with no chipping in the face, it may make more sense to repair the crack than to replace the tile. You can apply clear epoxy to the cracked tile, filling the crack and making the tile waterproof and structurally sound. If desired, you can use paint to hide the crack once it is filled.