Tile can be used as either a floor or wall covering. The underlayment is the middle layer between the tile and the subfloor or the wall and is critical to the durability and longevity of your tile. When damage occurs due to an unsuitable underlayment, it often must be replaced along with the tiles. Therefore, you can save a lot of time and money by choosing a suitable underlayment prior to installation.

What Floor Underlayment Materials Should You Avoid?

If the underlayment is uneven or prone to movement, it puts pressure on the floor tiles when walked on. This causes the grout in the joints to crack and the tiles themselves to break. The following underlayment materials should be avoided.

1. Old Flooring

In some rare instances, it is acceptable to install new tiles on top of existing flooring, such as linoleum or old tiles. However, this is only an option when the existing flooring is completely even and undamaged. Otherwise, you should remove old flooring whenever possible before installing new tiles. A new floor installed on top of the old may end up taller than the floor in adjacent areas. Furthermore, any structural problems present in the old floor will transfer to the new.

2. Plywood or Particle Board

These materials should never be used as underlayment, even if they are graded for interior use. The combined weight of tile and grout is too heavy for particle board, and exposure to water can cause plywood to swell. Cracking of the tile and grout can result.

3. Concrete Slab

Because of concrete's stiffness and rigidity, it might seem as though you could install the ceramic tile directly on top of it. It might be possible to do this if the concrete is completely even with no flaws, but even then it is risky. Concrete dries within a day or two but can take up to 15 years to cure completely. During this process, the concrete could crack due to shrinkage, and any tile or grout installed on top would crack too.

Which Materials Should You Use?

When choosing underlayment for a tile floor, there are a handful of potential options. Ultimately, the underlayment you choose may depend on the subfloor you have.

1. Membranes

Membranes are made of polyethylene and are available in rolls or thin sheets. Membranes are relatively easy to install and may offer additional benefits, such as soundproofing or waterproofing. There are also special crack isolation membranes that protect the tile from existing problems with the subfloor. If you suspect movement of the substrate, you may want to choose an uncoupling membrane that protects the tile by absorbing the movement.

2. Pourable Underlayment

Mortar is the most traditional type of pourable underlayment, but it is no longer the only option. Thin set is a highly adhesive cement mixture that is often used to install other types of underlayment but can also be used alone. If unevenness is a problem, a self-leveling product may present a solution.

3. Backer Board

Backer board is regarded as the preferable option for most tile installations. There are different varieties of backer board, but the standard variety is fiberglass facings on the sides of a solid concrete core. Backer board is very durable, but it is hard to cut and may present a challenge if you want to install the floor yourself.

What About Underlayment for Wall Tiles?

Wall tiles are not walked on and so are not subjected to the same pressure. Nevertheless, some wall underlayment are inappropriate. For example, tile should never be applied directly to plaster or stucco. The uneven surface makes it hard to get a good bond, and moisture can pose problems. Tile can be applied to painted drywall but never raw drywall without a primer coat at least. Otherwise, the paper coating may dissolve.

For over 20 years, Mosaic Tile Outlet has carried the best selection of floor and wall tiles. Check out our classic designs today.