How to Lay a Cement Board Floor

 Laying a cement board floor is an important step when you plan to tile a floor. In addition to giving the tile something to adhere to, it also helps prevent against inadvertent damage caused by a shifting subfloor. When done properly, it provides a durable and solid base for the ceramic tile to be installed.

1. Sweep the floor thoroughly to remove all dirt and debris.

2. Use a scraper to remove any high spots caused by drips of liquid nail or joint compound. If the floor was previously covered with another surface, care should be taken to also remove any remaining adhesive.

3. Nail down any nails or screws that are not even with the floor. If they are left sticking up, they may prevent the cement board from laying flat.

4. Sweep floor again to remove any debris.

5. Clean the floor using a bucket of water and a sponge. Work in small areas, thoroughly saturating the floor to catch any stray dirt and dust. Once the entire floor has been washed, rinse the sponge thoroughly and wipe the floor again with clean water.

6. Allow floor to dry thoroughly. If time is a concern, a fan may be used to reduce drying time, but make sure no debris is blown onto the floor.

7. Spread mastic using a trowel held at a slight angle. Work in three-by-five foot sections, covering each section with a piece of cement board before continuing to the next section.

8. Cut cement board as needed to make fit. If a cut is required, a carbide scoring tool or utility knife can be used to make straight cuts. For round or L-shaped cuts, use an angle grinder with a diamond grit blade.

9. Once entire floor has been covered by cement board, insert nails approximately six inches apart over the entire floor. A nail gun is faster, but if one is not available or there is no power, a hammer can be used instead.