Once you’ve determined the thickness of the underlayment you will use, the steps of installation are the same. Dry fit your sheets of cement board to the area you are tiling. To cut the board you can either use the side grinder with diamond blade, or you can score and break the material.
The cement tile department personnel can show you the available scoring knives. Your joints between sheets should not exceed 1/8 inch. It is also advisable to install the sheets perpendicular to the direction of the floor tile. This adds additional strength and stability.
Install the sheets one at a time. Mix your thinset according to the instructions on the bag. Lift one sheet (leave the rest in place) and spread thinset directly onto the bathroom floor filling the area left by the sheet (use a 1/4″ x 1/4″ notch trowel). Once you have filled the space place the sheet down onto the thinset. Secure the cement board with the screws using the pattern directed by the board manufacturer. Repeat with the remaining sheets of cement board until finished.
Apply the crack suppression membrane over the joints of the boards. You will use the flat trowel to apply a thin layer according to the manufacturers specifications. (e.g. 6-18″ width across the joint). This will distributed the stress caused by movement of the subfloor tile and prevent cracking in your wood marble tile. If greater protection is desired you can cover the entire floor with the membrane. Let dry for 24 hours.
Complete the installation. The remaining steps are identical to installing tiles price on a concrete slab, less one tip: Use a damp sponge to wipe the cement board prior to applying thinset. This will keep the cement board from drying the thinset too fast and allow proper adhesion to the wall tiles design.