And yes, it’s safe to have. In fact, not having a liner can be more risky than having one under the tiles. Installing a shower tray liner is a must and can mean the difference between an enriching everyday experience and a leaky bathroom.
It is recommended to use grout under all shower trays. Mortar reduces the risk of your pan slipping or breaking on an uneven surface.
If you want to lay tiles on your shower floor, you need a special shower tray. Otherwise, the tray will not withstand the tiling process. You should also keep in mind that tiling directly on the concrete subfloor is not a good idea.
Top mud. The rubber membrane in a shower is installed on a thin layer of mud leading to the drain and another layer of mud is installed on top of the membrane to form the base for the tile. This is typically around 2 inches.
Tarpaper helps prevent the subfloor from absorbing moisture from the pre-tile mix that is applied to it. So we laid out the tar paper at the bottom of our shower area where our front pan would go.
In bathrooms, all wooden floors, including chipboard and plywood, must be fully waterproofed over their entire surface, with the exception of the area under a molded shower tray or built-in bath, whether the shower is enclosed or not.
The wall plate must be installed 1/8 inch above the shower tray. If the shower tray is not present, the height of the wall board must be estimated, which can lead to inaccuracies and an expansion gap that is too big or too small.
The pan liner should end at least 6 inches above the framed or (roughened) curb level. This height allows for the application of concrete base and finishes to be applied.
He said that you can attach the pan liner directly to the subfloor, float your grout over it, and then attach your tiles. In addition, water would only hit the liner if the tile cracked or the grout bed failed, and that would be the tiler’s fault.
The best concrete mix for shower trays comes from Quikrete. They make two products, the first is called Floor Mud, the second is their sand/topping mix. Both are excellent for building a shower tray. Just like other types of concrete mix, there are DIY options.
Spray foam under a shower tray is an option to reduce flex. It’s not the only solution and may not be the best choice depending on your situation, but if you do decide to use it, make sure you go with a non-expanding foam.
Grout is a better choice for wet areas.
Although grout is more porous than grout, it works best for tiled shower walls and floors. This is mainly due to the way grout bonds to the backing plate, the concrete material that is placed behind tiles.