How to Lay Slate Tile With Grooved Backs

Prepare the slate tile for installation in an area separate from the place where you will be installing it. Open the containers and sort through the material to look for broken pieces or pieces that are too large or too small. Ordering 15 to 20 percent extra material is required for slate. Clean off the backs of the tiles you are using for the installation with a hand broom to remove any dirt and residue so the tile will bond with the thin-set.

Lay out the installation area for the slate tile. Place several pieces in a row — at least enough for 2 feet — with a grout joint between them, and measure the pieces. Measure the installation area. Use the laid-out pieces to determine the size of the cuts on the floor if you center the room, and the size of the cuts if you start with full tile in the visible areas and use cuts in the least visible areas. Adjust the measurements until you are satisfied.

Measure out from your starting point the length of two tiles with a grout joint between them, and mark that distance on the floor. Repeat the process on the same wall but somewhere else along it, preferably several feet down from your first mark. Snap a chalk line between these two lines to place your first reference line.

Measure out from the starting point of your perpendicular line the length of two tiles, and place that mark on top of the chalk line. Take the framing square and draw a perpendicular square line with a pencil opposite the first chalk line on your new mark. Snap the chalk line over that mark for your second control line.

Snap more grids by measuring back from the control lines you made in Steps 3 and 4, and mark more lines on the floor. Use the same 2-foot measurements to mark your lines. Check them occasionally with a framing square to make sure you are getting everything nice and square and in line with the control joints.

Choose a starting point and work backward from there. Spread a layer of thin-set mortar onto the floor in one of the grids, right up to the edge of the lines. Place your pieces of slate tile in the bed of mortar without regard to the grooves, and press each piece firmly down. Align the pieces with the grid lines. Check them for grout joint width and adjust if necessary, as slate is not regular in size and you can only create semistraight grout lines.

Work your way out from the starting point and install the tiles grid by grid. Adjust the grout lines as you work your way back, keeping an eye on overall straightness within the grids rather than with tile spacers, as they cannot work in this instance. Allow the installation 24 hours to dry before grouting.