Setting Shower Floor Mosaic and the First Row of Subway Tile

The mosaic shower floor had to set overnight so the Schluter All-Set could cure enough to support a person's weight, which means wall tiling cannot start right after the floor goes in. That pause sits between the two halves of this stage of a walk-in shower build: the marble mosaic floor, then the first row of subway tile on the walls.

Laying out the floor

The drain is centered in the space, and the Schluter system left some room to adjust before the drain and thinset were set. The mosaic has square edges, so the layout was shifted to get solid tiles rather than slivers. The plan starts with the center tile, centers the drain in it and works left and right. Grout lines should run parallel to the walls. The installer dry sets the layout first.

The edges were trimmed on a wet saw, which traps airborne particulate in water. Water can weaken the glue holding the mosaic sheet, so a tile may come loose and need to be picked up later. Ear protection and safety glasses are advised.

Setting the drain and floor tile

The drain flange went into a bed of All-Set, with the dimension confirmed at 14 3/8 and the drain squared to the wall. Thinset was packed under the corners for support. The drain sits high at first, on purpose, and is pressed down to its final position once the tile is placed.

Because the tile is marble, a natural stone, the thinset is combed and then knocked down to avoid air pockets under the stone. The tiles were placed by hand, and the slope into the drain can be felt.

Planning the wall tile

Waterproofing, patching and Kerdi-Band corners were complete. The full height was about 85 1/2 in. The goal was a roughly 2 in. tile at the top and 2 3/4 in. at the bottom. Subway tile has a built-in lug, so no spacers are needed.

A Bosch laser level showed the corner was slightly raised from the Kerdi-Band, so the bottom cut is 2 1/2 in. on the right and 2 3/4 in. on the left. An eighth of an inch is left between the pan tile and the wall tile for siliconized caulk matched to the grout color, in the inside corners at the wall and at the floor. The caulk and grout do not keep water out; the waterproofing layer behind does.

Cutting and setting the first course

The back wall center was marked at 29 1/2. Tiles were marked, numbered on the back and cut on the wet saw by taking the line. Pencil is used rather than grease pencil, and the cut is lined up by sighting down the blade. Blade deflection left tile one slightly taller than its neighbor, so small shims bring each tile to the laser line.

The floor was covered with paper and tape. Thinset was combed with a 1/4 by 1/4 trowel, and tiles were set from the center line, then shimmed to the laser line with consistent joints.