Can You Put Cement Board Over Tile? Tips & Costs

Encountering a tiled surface when planning a renovation is almost inevitable, and a frequent question that arises is whether you can put cement board over tile. The short answer is a definitive yes, but success hinges entirely on meticulous preparation and the correct materials. This method is a standard practice for installers looking to add a fresh, waterproof layer or to prepare a robust substrate for tile, vinyl, or other finishes.

Why Install Cement Board Over Existing Tile

The primary drivers for covering tile with cement board are transformation and restoration. If your current tile features an outdated pattern or color, laying a new layer provides a blank canvas for a modern design without the labor-intensive demolition. Furthermore, if the original grout lines are cracked or the tile is compromised, cement board acts as a stable, unified surface that eliminates the risk of cracks traveling through to your new top layer. It is also the essential foundation for waterproofing in wet areas, creating a solid barrier that protects the substrate behind the tile from moisture damage.

Structural and Preparation Considerations

Before proceeding, you must evaluate the condition and structure of the existing tile. The substrate must be solid; any loose or hollow-sounding tiles need to be addressed or repaired. You are essentially adding weight to the floor or wall, so you need to confirm that the joists or framing can handle the combined load of the cement board, thinset, and the new tile. Height is another critical factor—adding 1/2 inch or more will raise the floor level, which might affect transitions with doorways or fixtures.

The Right Materials for the Job

Not all cement board is created equal, and selecting the right type is crucial for the longevity of the installation. For areas exposed to moisture, such as bathrooms or laundry rooms, standard cement board is suitable, but you must ensure the thinset and grout used are also moisture-resistant. If you are dealing with a significant height difference, a self-leveling underlayment can create a seamless transition. The fasteners are equally important; use a rust-resistant screw designed for cement board, spacing them appropriately to secure the board tightly to the rigid tile surface beneath.

Step-by-Step Installation Process

To achieve a professional result, follow a systematic approach. Begin by meticulously cleaning the tile surface to remove any residue or oils. Next, apply a layer of modified thinset troweled in a notched pattern to ensure a strong bond. Lay the cement board sheets horizontally over the tile, ensuring the joints do not align vertically with the joints in the layer below—this staggering pattern significantly increases the integrity of the surface. Fasten the board every 6 to 8 inches, and be sure to countersink the screws slightly and fill the heads with thinset to create a perfectly flat plane.

Sealing and Finishing the Surface

Once the cement board is fully installed, the next phase is sealing. Joints must be filled with a fiberglass mesh tape and covered with a waterproof joint compound to prevent moisture infiltration. After the compound dries, the entire surface should be sealed with a penetrating sealer or a cement board-specific membrane. This step is non-negotiable, as it protects the core of the board from humidity and ensures that your new tile installation lasts for years without degradation.

Finally, regarding the grout you choose for the new tile, you have options. While sanded grout is generally preferred for the larger joints found on floors, unsanded grout works for tighter spaces. The color of the grout can dramatically alter the appearance of the final design, allowing you to match, contrast, or highlight the tile pattern. By treating the existing tile as a permanent, stable base and respecting the necessary steps for the cement board, you can confidently answer the question of whether you can put cement board over tile with a resounding success.