Setting Irregular Slate on a Concrete Pad

Measure the width and length of the concrete pad with a tape measure. Multiply the two measurements together to determine the surface area. Divide the surface area by the square footage of a single piece of slate to determine how much slate tile to purchase. Typically, slate tile comes in 12-by-12 inch dimensions, which equals 1 square foot. Sweep the floor free of any debris. Clean the concrete pad thoroughly with soap and water. Use a degreaser only if there is any oil or grease on the concrete pad. Allow the concrete pad to dry.

Find the center of the pad by marking the center point on each edge of the concrete pad. Snap a chalk line between the center marks on opposite edges. Test-fir one full row of slate between two opposite edges. Center each piece of tile to the adjoining tile. Use 3/8-inch spacers between the tiles. Cut the two end pieces with a wet tile saw. Place all of the tile off to the side but in the same order it was laid.

Mix together water and thinset in a 5-gallon bucket with a drill equipped with a paddle bit. Add small amounts of water until the mixture has the consistency of peanut butter. Use a 3/8-inch notched trowel to spread thinset across the floor where the first row of tile will be laid.

Lay the first row of tile. If the tile has different thicknesses, back-butter the thinner pieces of tile with additional thinset and use a level on the top surface of the tile to ensure it is set level. Back-buttering is the process of spreading additional thinset on the bottom surface of a tile piece. Remove any excess thinset with a margin trowel and a damp sponge.

Measure from the edges of the largest pieces of slate and mark the general size of the tile on each side of the row that is now laid. Snap a chalk line the entire length of the pad at those measurements. Test-fit the next rows of slate with the pieces staggered. Each piece in the same row should be centered on each other. Staggered pieces should lay halfway between the pieces of slate in the adjoining row. Use spacers in between the slate tiling for the row being laid but not in between the rows. The varying sizes of the slate will prevent the use of spacers in between each row. Use the chalk lines only as rough guides. The grout lines in between each row will have to be visually adjusted to keep the rows fairly evenly spaced.

Slide each row of tile out of the way then spread thinset for the new rows. Repeat this process until the entire floor has been laid. Allow the tile to set up overnight. Thoroughly clean the tile with water and a sponge.

Mix grout and water together to the consistency of cake mix. Fill all of the grout lines with grout applied with a rubber trowel. Clean any excess grout off of the slate with clean water and a sponge. Allow the grout to cure for 72 hours. Seal the grout and the slate with sealer and allow it to dry.