How to Make a Tile Floor Hearth

Check if the substrate of your hearth is concrete or wood. If it is concrete, fill any holes, or unlevel places with thinset mortar, using an un-notched trowel. If it is wood, cut a piece of backer board with the utility knife to the size of your hearth, glue it down with construction adhesive, and drill it down, one screw every 12 inches. Fill the screw holes with thinset.

Measure the entrance of the firebox to find the center. Draw a line from the center point to the edge of the prepared substrate. Divide the length of the hearth in two, drawing a line along the length, which intersects the center line. Draw two more lines from the edges of the firebox to the end of the hearth substrate. You have an inner quadrant, and an outer set of squares onto the hearth space.

Dry lay your tiles, starting with the edge squares of the inner quadrant. Leave 1/8 inch between tiles to account for grout. Fill the entire inner quadrant, then the outer set of squares with tiles. Mark tiles which need to be cut to fit.

Transfer your tile design to the floor beside the hearth, making sure it is placed the same as your hearth design.

Put on your protective mask, eye goggles and ear plugs, then turn the wet saw on, making sure there is plenty of water flowing before cutting the tiles that need to be trimmed, along the marked lines. Feed the tile into the blade with light pressure; you don't need to force it through.

Fill one square of the inner quadrant with a layer of thinset, around 1/8 inch thick. Use the flat trowel to place the mortar, then use the notched trowel to scrape ridges. Lay the tiles of that quadrant square, being careful to replicate the design, and to leave the required grout space---check the quadrant with the level to make sure the surface is even, gently tapping down tiles that are too high.

Repeat with the remaining quadrants, until the entire hearth is filled. Clear away any mortar that has squished through the grout space with a grout sponge. Let dry for 24 hours.

Mix the grout with water per the grout manufacturer's instructions. Hold the grout float at an angle, and spread the grout diagonally across the tile joints and into the space between the tiles. Grout the entire surface of the hearth, bar the outer edges. Let dry for around 30 minutes.

Wipe away excess grout with a damp cloth, then leave to dry overnight.

Caulk the outer edges of the hearth with a caulk that matches the grout color. Smooth the edges with a wet finger. Let the hearth cure for three days before giving it a good clean with a damp cloth and before lighting a fire.