We are often asked if it is possible to install new tile over existing tile, especially on floors. The answer is yes! Well, maybe. There are several things that need to be inspected before this will be successful. These are as follows:
- The condition of the existing tile. If some of the existing tiles are loose, or missing, that is an issue. Most often the tile substrate has failed or is inadequate, or the tiles were not installed properly. Installing new tile on top of this scenario will result in failure. We would typically tear out the existing tile and substrate and start from scratch.
- The existing tiles are tight but there are cracks in the floor. Most likely, the tile substrate has failed or is inadequate. Caution should be taken if new tiles are to be installed over this scenario. Often, the cracks permeate through the new tiles over time. Depending on the elevation of the floor, if would be possible to prep the existing tile surface and install Ditra underlayment over the existing tiles. The new tile would then get installed over the Ditra. The Ditra will prevent the permeation of the cracks through the new tiles.
- Existing doors in and out of that space. Adding an additional layer of tile will raise the height of the new floor up to ½” depending on the thickness of the new tile. Sometimes this increase in floor elevation impedes the operation of the existing door. Removing and cutting the door is the answer, but should be known in advance of the tile over tile installation.
If the existing tile floor is not cracked and is tight to the substrate, installing new tile over the existing can be done. The process that we have found to be very effective is to wash the existing tiles with a mild solution of diluted Muriatic Acid. This will remove any residue or dirt from the tile surface. Once the surface dries, you are ready to start installing. Using an unmodified thin-set to adhere the new tiles has worked very well to bond the new tiles to the existing. It is very important to use the correct sized notched trowel to spread the thin-set on the tile surface and then to “butter” the backs of the new tiles. This process will ensure full contact of the thin-set and full bonding between the new and the existing. Happy tiling!