What Mortar Does: How to Cover a Fireplace With Slate Stone

Mix up a batch of thinset in a bucket according to the manufacturer’s instructions. Add the water to the dry mix slowly and stir it with the drill and paddle until you have achieved a creamy consistency. Spread it onto the existing brick or block fireplace to coat the surface with mortar and fill in the joints between the bricks or blocks. Let this skim coat dry for 24 hours.

Lay out several tiles in a row to determine how you want to lay out your fireplace with slate tile. Use the level, tape measure and pencil to draw level and plumb lines on your fireplace to guide the outer perimeters for plumb and the horizontal joints for level. Use those lines as a reference point for smearing your thinset.

Mix up another batch of thinset and spread a layer of thinset mortar on top of the skim coat of thinset along the bottom area of your installation with the notched trowel. Press the slate stone into the mortar and work your way in from the outside perimeter lines, with cuts against the fireplace (if necessary) and full tiles on the outer edges. Work your way up from the bottom so you can stack the stone.

Install the second row the same as the first, with tile spacers and wedges between the tiles to help keep the joints uniform. Add extra thinset to the backs of the stones as necessary to build them out to match other, thicker stones. Use the pencil lines as a guide as you work your way up from row to row.

Make any cuts for your slate stone fireplace on the tile wet saw. Dry off the tiles with an old towel so there is no water to harm the bond between mortar, stone and the fireplace skim coat. Use masking tape to hold the tiles hanging across the top of the fireplace in place. Allow a minimum of 24 hours before grouting your new slate stone fireplace.