Is It the Best to Use Mastic or Mortar on a Shower Wall?

Mastic

• Mastic works well as a tile adhesive on a variety of surfaces in the home. Since mastic often comes in tubes like caulk, it also has a simpler means of application. You can simply squeeze the adhesive out onto a surface much as you would any standard glue, and then apply tiles. In addition, because mastic is composed of an organic material, it is environmentally friendly. However, this environmental advantage proves a downside when it comes to shower wall. Like any solely organic liquid, mastic breaks down over time with exposure to moisture, making it ineffective in a shower environment.

Thinset mortar

• Thinset mortar is mostly manufactured from organic ingredients. The composition includes clay, lime and sand, but it also includes a chemical to help keep moisture in the adhesive, making it long-lasting. The advantage of thinset mortar over mastic is that mortar doesn’t break down when exposed to water, so it holds up more effectively in humid conditions like a shower, making it the better choice on a shower wall. The downside to mortar is that it is thicker than mastic and must be applied with a trowel.

Protecting the Adhesive

• Whether you choose to use mastic or mortar on a shower wall, when you install the tiles in a shower, you must leave spaces between them in accordance with the manufacturer’s guidelines. However, these spaces leave the adhesive behind the tiles exposed to direct water. To protect the mastic or mortar from moisture, all tile jobs require grout in between the tiles and caulking around the perimeter of the shower wall and wherever tiles meet the shower fixtures, such as the base of the shower.

Seal the Tile Job

• Although grout fills the spaces between tiles to prevent water from directly hitting the adhesive, grout has a porous surface, meaning that water absorbs into the grout and can eventually leak through to the tile adhesive. Prevent moisture problems by applying a waterproof sealer over the grout between the shower tiles once the grout dries. If you use non-coated tiles, such as slate or stone, you should apply sealer over the tiles as well.