Can you place a cement backer board over a tile floor?

Although it is technically possible to place cement backer board over a tile floor, it is generally not recommended due to several considerations.

1. Height and Door Clearance: Installing cement backer board over a tile floor will increase the height of the floor, potentially causing issues with door clearance. This could result in difficulty opening and closing doors or the need to trim doors.
2. Added Weight: Adding cement backer board on top of a tile floor will increase the weight on the subfloor, which may exceed the load-bearing capacity of the structure.
3. Bonding Issues: Placing cement backer board over an existing tile floor may hinder the adhesion between the backer board and the subfloor, potentially leading to issues like tile delamination or cracking.
4. Grout Lines: Installing cement backer board directly over an existing tile floor will result in grout lines showing through the new tile installation, which may affect the appearance and aesthetics of the finished project.

Alternative Options:

Instead of placing cement backer board over an existing tile floor, it is recommended to remove the tiles before installing the backer board. This ensures a proper and secure bond between the backer board and the subfloor. The steps for this process typically involve:

1. Removing Tiles: Remove the existing tiles using a hammer and chisel or a tile removal tool.
2. Preparing the Subfloor: Clean the subfloor thoroughly, ensuring it is free of any debris or adhesive residue. Repair any damaged areas, level the surface if necessary, and allow it to dry completely.
3. Installing Cement Backer Board: Cut the cement backer board to size and lay it over the prepared subfloor. Secure the backer board using screws, making sure to follow the manufacturer’s guidelines.
4. Waterproofing (Optional): Apply a waterproofing membrane or a sealer to the cement backer board if added moisture protection is desired.
5. Tile Installation: Once the cement backer board is installed, proceed with your tile installation as usual, following the manufacturer’s instructions.

While it is technically possible to place cement backer board over a tile floor, it is generally not recommended due to height and clearance issues, potential bonding problems, increased weight, and the visibility of grout lines. It is best to remove the existing tiles before installing cement backer board for a secure and long-lasting tile installation. Always follow the manufacturer’s guidelines and proper installation techniques to ensure a successful outcome.