Tadelakt: Plaster in Showers

People frequently ask about plaster in wet applications. Behind a sink, or in a bathroom or a kitchen. Depending on the plaster there are different ways of keeping the water from affecting the integrity and look of the plaster. Most manufacturers offer some type of top coat to repel the water, usually some type of acrylic or silicon sealer. If we really want a true water-repellent finish, it is not a specific product, but rather a specific technique that must be used. Tadelakt.

Tadelakt is a technique whose roots are born out of Morocco. The word refers to the technique of rubbing and polishing the plastered surface to achieve the smooth finish. The biggest differences between a Tadelakt wall and a highly polished lime plaster wall such as a grassello are lime sands in the plaster and the use of black soap during application.

The olive-based black soap and polishing is the cornerstone of Tadelakt technique. As the final coats of the plaster are curing black soap is applied to the surface of the wall and polished into it. The carbonic acid in the limestone reacts with the fats and glycerin in the soap to create three different calcium salts which are hydrophobic. This layer of plaster is chemically altered to shed water. The beauty of such a wall is that it only needs to be cleaned with black soap and it is naturally anti-microbial and nearly impossible for mold to grow because of the natural properties if the lime. When used in a shower, there is no more scrubbing grout, no more dark mold stains in the corners.

The beauty of tadelakt is astounding and I love the look and the finish. A tadelakt wall will develop its own personality and look over time. Some walls will form micro-cracks that almost give it a crackled undertone, some will mottle out over several months increasing their depth and character. They are a living wall in the house.

When thinking about using plaster as shower walls, there are several things to think about. How sturdy is the wall the plaster is going to be applied to? 1/2 green sheetrock is not going to cut it. A strong cement board over studs at 16" maximum is a good place to start. Kerdi also works well. The thing to keep in mind in a remodel is that you may have unforseen framing costs once a shower wall is opened up. If its a new build, simply plan accordingly. The other thing to think about is adjoining material, how is the plaster going to meet the rest of the walls? The ceiling? the shower pan? While you can plaster down to the tile on the floor, I've taken to having the shower pan tile run up the wall and inch or two. This is a bit more of a fool proof way to maintain the integrity of the plaster and tile job. If you do decide to plaster down to the tile, the floor pan pitch is important, you really want to minimize water collecting at that seam and potentially wicking up the back side of the plaster or down into the tile mortar.

Plaster walls in a shower? Absolutely love it! And I'm sure you will to, if not for no longer having to scrub grout, or for being able to use a simple soap as a cleaner, then for the sheer beauty of a living wall in the place we all start the day.