Fixing a Leak Beneath Bathroom Tile

Man repairing a sheet of mosaic ceramic tiles on a shower floor.
What You'll Need
Flat bar
Green board
Cement board
Screw Gun
Drywall compound
New tile

When you suspect a leak under the bathroom tile, you should take a few steps to fix the leak before other problems develop. This is one of those fixes that needs to be done quickly before it escalates into bigger, more complex issues. Water leaks under the bathroom tile are especially dangerous and can result in structural damage.

Here is a quick way to fix a leak beneath your bathroom tiles.

Step 1 – Examine the Tile

Really get down close and examine the tile carefully for any breaks or cracks. Even small things like separations or deteriorating caulk could be clues.

One thing that won’t give you a clear idea here is water. As strange as that sounds, given that you’re looking for a water leak, the water may exit and be visible at one area of the floor, but the leak’s actual point of origin could still be elsewhere. Plus, under the right timing, any water you see could just as easily be there because the shower curtain wasn’t positioned well enough.

Step 2 – Remove the Tile and Grout

Using a screwdriver as well as a chisel, begin scraping the grout out from the surrounding tiles of the area affected by the leak. Remove any sealant and adhesive you can see that was likely added during the original install.

Step 3 - Remove the Damaged Surface

If your initial leak was indeed coming from below the bathroom tile, chances are that there is considerable water damage to the wall or floor. If this is the case, remove the damaged section so that you can replace it with new material. Just covering the area with fresh tile without actually replacing the surface will leave behind moisture and allow mold and mildew to grow. Wherever you notice water damage, fix the leak that caused the damage in the first place, repair the damage, and replace your tile immediately.

Water and water damage are issues that get worse the longer they're left unchecked.

Step 4 - Repair the Leak

Water may be seeping through the surface of the tile, in which case you don't have to do any plumbing repairs, but if the leak is in a wall, chances are it's from a supply line. If it's in the floor, it could be from the supply or from the drain. Locate the source of the leak and perform the necessary repairs.

The actual specifics of the repair will vary depending on your plumbing configuration.

Step 5 - Repair the Damages Surfaces

Now that the leak has been addressed, replace the water damaged material you removed to access it. Use materials appropriate for the setting, like green board drywall for the walls or cement board for the floors.

If your bathroom is older or you find that the materials were ill suited for being in the presence of water, which is abundant in a bathroom setting, you might want to treat this as an opportunity to upgrade to more modern, water-resistant building materials.

Once the repairs are complete, make sure everything is clean, dry, and sealed.

Step 6 - Fill the Tub

Apart from a plumbing problem, there are two main reasons tile will leak. The first is faulty installation of the tile, and the second reason is that the tub may have settled. When the tub is filled with water, or there is weight in the tub, it can cause the tile beneath it to flex and compress and cause the tub to settle. After a short period of time, this process can cause cracks in the grout or tile.

Fill the tub before installing the new tile so that the tub is already settled into its heaviest position. This way, the new tile will not be forced to react with strain against the weight of the full tub, as that's the condition it will be accustomed to.

Step 7 - Reinstall Tile

After the damaged area is clean and free from dirt and damage, apply a thin layer of mortar, and set the new tiles by pressing them into the mortar. Once the mortar has dried, mix a small amount of grout and apply to the tile to cover all the spacing between the tiles.

Once everything has dried, apply a bead of silicone sealant to all the seams where the tub meets the tile to cover the grout and protect the tile from future leaks.