How to Add Slate Tile to a Fireplace

Apply a thin layer of thinset mortar over any bricks or field stones that may be in place on the surround, using a trowel. The thinset will fill the old mortar lines and create a smooth, even surface for the slate tiles to adhere to. Allow the thinset to cure for 24 hours before tiling.

Measure the legs of the surround and choose slate tiles that are either the exact width of the surround, stacked on top of one another for a contemporary look, or use multiple sizes of slate to fill the area in a pattern for a more eclectic feel. If need be, cut the tiles to fit the legs of the surround on a tile saw to achieve the look you desire.

Apply thinset mortar to the back of each tile and install them on the surround. Slate tiles are uneven in thickness, so this step is crucial in getting an even installation. Press each tile firmly into place on the surround. Twist the tile slightly while placing it to ensure a good bond.

Cut the edge tiles, or tiles that are too large for the surround on a tile saw so that they fit the legs of the surround evenly. The top of the surround should feed into the legs evenly, so cut the tiles to accommodate. Allow the thinset to cure for 24 hours after installation.

Seal the tiles with an impregnating sealer; slate is a natural stone and is porous, the sealer will help keep the grout from absorbing into the tiles. Use a foam paintbrush to cover the tiles in sealer and wipe up the excess with a cloth.

Press standard gray grout between the tiles with a grout float. Wipe up the excess grout with a damp sponge. Once the grout is dry, enhance the color of the slate tiles by applying a second, color-enhancing sealer.