Ceramic and porcelain tile are among the most rigid materials for flooring. They require a subfloor that’s designed to account for this, without any fluctuation or movement. If ceramic or porcelain tiles are installed on an uneven surface, you run the risk of allowing the tiles to crack or loosen. Here are some instructions on how to prepare your subfloor for a tile installation.
1. Installing ceramic tile and porcelain tile over a concrete slab
- Repair all cracks and uneven patches in the concrete subfloor prior to the installation – especially important if the tile is being directly bonded to the concrete.
- In case of subfloors 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.
- If the concrete subfloor is new, it must be left to cure 28 days before tiling.
- 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.
2. Installing ceramic tile and porcelain tile over a plywood 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 strong enough for a tile installation.
3. Installing ceramic tile and porcelain tile over vinyl flooring
- Non-cushioned vinyl and linoleum that is structurally sound and free of excessive movement can act as an appropriate subfloor.
- Cushioned vinyl is not an appropriate subfloor. You will need to 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.
4. Installing ceramic tile and porcelain tile over an existing tile floor
- 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’re installing directly over the old tile flooring, rough up the existing tile with sand paper. Clean with a 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.
Subfloors to avoid for tile installations are those that tend to flex, expand, contract, or warp. Any excessive movement will loosen the tile and pop the grout. Unsuitable subfloors must be replaced or covered with a suitable underlayment. Here’s a list of no-go subfloors:
- Cushioned vinyl
- Perimeter installed vinyl
- Single layered plywood
- Flake board
- Chip board
- Hardwood (strip) flooring
- Luan plywood
- OSB boards
- Sheet metal
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