Basic subfloor preparation instructions for installing ceramic tile

Ceramic tile are among the most rigid materials for flooring. They require a subfloor that is designed to account for this, without any fluctuation and movement. Here are some basic instructions about subfloor preparation for tile installation.

• Repair all cracks and uneven patches in the concrete subfloor prior to the installation, if the tile is being directly bonded to the concrete.

• In case of sub floors with large cracks, consider the possibility of removing a large section of concrete slab and replacing it with a new one instead of patching all the cracks.

• For bad cracks in the concrete slab, smooth it with concrete filler, or similar compound.

• Cleanliness is paramount. Besides any surface materials, be sure to remove any grease stains, or other substances that have stained the slab as best you can.

• Cement backer board can provide a solid, flat surface to install tiles on if you have a wood subfloor.

• A plywood subfloor must be structurally sound and able to support the installation. Tile floors are heavy and tile is a hard material. It will break or dislodge if the surface bends under the load.

• Remember that you need a very flat surface to work on. If needed, sand the plywood down to level the subfloor.

• Plywood must be installed over an adequate subfloor and must be at least 1 1/8" thick when combined with the subfloor. Interior-grade plywood and particleboard are not considered a strong enough for a tile installation.

• Remove the vinyl floor and any remnant adhesive used for the vinyl installation.

• In some cases, you will be able to remove the vinyl itself, but not the adhesive. Use the type of thin set that is recommended by the backer board manufacturer.

• If it seems difficult, you might want to lay down a backer board with thinset.

• You can either leave the tile floor in place and apply thinset directly over it, or remove the tile with a hammer, depending on how high the floor will need to sit relative to doors and other interior elements.

• If the existing tile floor is set over a mortar bed it may be hard to remove the tiles without removing a lot of the mortar bed.

• If you are doing installation directly over the old tile flooring, rough up the existing tile with sand paper. Clean with degreaser and test a small area overnight for bonding.

• Also, check the height of the floor with the height of doors and cabinets. Any good thinset can be used to install your new floor.

For installations over vinyl or wooden substrates, you will need a high quality latex modified thin set mortar.