Best Subfloors to Use For Laying Ceramic Tile

Man Laying Tile Floor
Man Laying Tile Floor. Getty / Jodi Jacobson

Ceramic and porcelain tile is delicate  Because of issues of moisture, movement, and adhesion, tile will work with certain types of subfloor--and can go dramatically wrong with other subfloor materials.

Beginning with the best subfloor or underlayment materials for tile.

Cement-Based Backer Board

Backer board is made for tiling. Backer board goes under various brand names, such as DensShield, Hardiebacker, and WonderBoard.

Tile backer board is always a preferred ceramic tile underlayment.

Exterior Grade Plywood

Exterior plywood accepts tile, without swelling up like interior-grade plywood.

Since cement board is cheap and easy enough to lay down on plywood, it makes little sense to skip this step. However, if you would like to install tile on plywood subfloor, it is possible.

In short, you would put down two layers of plywood. Screws from the top layer must not run all the way down to the joists.

One Layer Resilient or Vinyl Flooring

Tile can be installed directly on vinyl flooring.

Not only must this must be sheet vinyl flooring, but it must be full contact, as well. Vinyl flooring glued or stapled only at the edges will not work as it is prone to movement.

To test if your vinyl floor is full contact, use a utility knife to cut a small slice at the center of the floor. Use the blade tip or sharp screwdriver to try to lift up the vinyl.

If it does not lift, it is full contact vinyl.

Overly glossy, cushioned, and tile vinyl floor will not work as tile subfloor.

Concrete Slab

Concrete slab is a good ceramic tile underlayment. Be careful of the expansion joints. If you tile over the expansion joints, the tile will crack.

To reduce the possibility of cracking, use an intervening material called uncoupling membrane.

An uncoupling material disconnects tile from its concrete subfloor. Because concrete can crack, these cracks transmit the same to the tile above. Uncoupling membranes effectively break this transmission domino effect..

Available under the brand names Schluter Ditra or Redgard Uncoupling Mat, this product is sometimes called anti-fracture membrane, crack isolation membrane, or crack suppression membrane.

Unsuitable or Poor Materials

  • Interior-Grade Plywood: This plywood will swell upon contact with water.
  • OSB Wood: Like interior plywood, OSB does not perform well with water.
  • Multi-Layer Resilient or Vinyl Flooring, Sheet: One layer of vinyl floor is fine. More than one layer isn't.
  • Resilient or Vinyl Flooring, Tile: Tile vinyl flooring has countless seams that will allow for moisture intrusion.
  • Drywall, Large Expanses: Because drywall has a paper outer layer, large applications of ceramic tile will eventually weaken and pull off that paper.

Notes

It is worth mentioning that you can apply ceramic tile directly to drywall on vertical surfaces, in limited areas.

Specifically, it is acceptable to tile directly on drywall for a kitchen or bathroom backsplash that is no more than a couple of feet high.

Also, note that the drywall cannot be painted. Bondera tile mat is a good non-thinset adhesive method of attaching tile to drywall.