Subfloor

• Slate tiles require a subfloor that is at least 1 ½ inches thick. If the subfloor is not thick enough, you must secure cement board or ½ inch plywood over the existing floor. If skirting board is installed around the base of the walls, pry it away. Use a pry bar to gently pull the boards from the wall so they don't crack. When you're ready to begin installation, vacuum the subfloor to ensure the mortar will adhere to the surface.
  
  

Find the Center

• Slate flooring tiles are typically laid from the center of the floor outward. Working from the center ensures the rows will be straight. It also ensures end tiles will be the same width if they need to be cut to fit. Find the center point by locating the middle of each length of wall. Snap a chalk line across two corresponding points on the walls. Hold the chalk line over the next set of midpoints and check that the lines are square with a carpenter's square. Adjust the second line if necessary, and then snap it to identify the center point of the subfloor.
  
  

Dry-Lay

• Once you spread the mortar, you have a limited amount of time to lay the tiles before it begins to harden. Dry-laying the tile prior to mixing the mortar saves valuable time. The first tile should be placed in one corner of the center point. If the tiles range in color hues, mix the placement of dark and lighter tiles to give the floor an even textured look. Tiles will also range in thickness. It's advantageous to place the thicker tiles near each other as they will require less mortar than thin tiles in order to produce an even floor. Set rubber spaces between the tiles and mark the cut line over each end tile. Wear safety gear to protect your eyes when cutting tiles with a wet saw.
  
  

Set the Tiles

• Slate tiles adhere to the floor with a layer of thinset mortar. Spread enough mortar over the surface to set six tiles at a time. Set the tiles in a row and press them gently into the mortar, then lay a board over the tiles and apply even pressure to the board. Continue in this pattern until the entire floor is laid, setting a bubble level on the board to check that adjacent rows are level. Once the mortar sets for a day, fill the gaps between tiles with sandless grout to prevent scratches on the grout.