Should You Install Cement Backer Board on a Concrete Floor for Tile Installation?
Understanding the Purpose of Cement Backer Board
Cement backer board is a cementitious material used as a substrate for tile installation. It provides a flat, hard surface that bonds with thinset adhesives and mortars, creating a stable base for tile. In traditional tile installations, cement backer board is typically screwed to plywood or OSB subfloors or wall studs.
Cement Backer Board on Concrete Floors: Is It Necessary?
When it comes to tile installation on concrete floors, the use of cement backer board is generally not necessary. Concrete is already a cementitious material, making the addition of cement backer board redundant. In fact, installing cement backer board on concrete can be detrimental to the overall project due to the following issues:
- Unnecessary Cost and Labor: Cement backer board adds unnecessary cost and labor to the project.
- Height Issues: Cement backer board can raise the floor height, which may not be desirable in some installations.
- Poor Fix: Some tilers may use cement backer board as a quick fix for underlying concrete problems rather than properly repairing the concrete.
- Invalidated Warranties: Major cement board manufacturers typically recommend against installing cement backer board on concrete or specify other installation methods. Installing cement backer board on concrete may void the manufacturer’s warranty.
Alternative Solution: Uncoupling Membrane
A better alternative to cement backer board for tile installation on concrete floors is an uncoupling membrane. Uncoupling membranes, such as Schluter Ditra, are designed to prevent tile cracking caused by minor changes in the concrete substrate. They mitigate the effects of concrete movement, reducing the risk of tile failure.
Preparing the Concrete Floor
Before installing tile on a concrete floor, it is important to prepare the surface properly. This involves:
- Resurfacing: Repairing any holes or cracks in the concrete using Portland cement-based fillers.
- Creating a Porous Surface: Removing paint or other coatings from the concrete using sandblasting, sanding, or grinding to create a porous surface that will bond with thinset mortar.
Installation Process
Once the concrete floor is prepared, tile can be installed directly onto the concrete using thinset mortar. Screws are not recommended for attaching tile to concrete, as they can damage the concrete and create weak points.
Additional Considerations
- Deflection Requirements: The concrete floor must meet specific deflection requirements (L/360 for tile and L/720 for stone) to ensure a stable base for tile installation.
- Thinset Mortar: The thinset mortar used to install tile on concrete should be specifically formulated for use on concrete substrates.
- Professional Installation: It is recommended to hire a qualified tile installer to ensure proper installation and avoid potential issues.
By following these guidelines and using an uncoupling membrane instead of cement backer board, you can achieve a durable and professional-looking tile installation on a concrete floor.