Step 1: Prepare the substrate

prepare teh substrate by smoothing the level
Photo: Kolin Smith
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If the hearth area has a concrete-slab substrate, make sure it's level and smooth. If not, mix a small batch of thinset mortar with latex additive following the directions on the packaging. Using the unnotched edge of a trowel, skim a coat of thinset onto the concrete to fill voids and smooth the surface. Allow to dry to the touch before continuing.

If the substrate is plywood, measure the area. Transfer the measurements to a sheet of backer board. Using a utility knife, score the board along the mark. Stand the board up and snap it along the score line. Then cut through the fibers at the snap line.

Glue the board to the plywood with construction adhesive. Using a drill/driver, screw the backer board down with fasteners placed every 12 to 16 inches. Fill the screw holes with thinset.

Tip: Before you begin, protect the finished floor around the hearth with plastic sheeting and painter's tape.
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    Tools List

    • utility knife
      Utility Knife
    • drill
      Drill/Driver with mixing paddle
    • notched trowel
      3/8-Inch Notched Trowel
    • caulk gun
      Caulking Gun
    • wet saw
      Wet-cutting Tile Saw
      (rents for about $40 a day)
    • four-foot level
      4 Foot level
    • putty knife
      Putty Knife
    • rubber float
      Rubber Grout Float
    • grout sponge
      Grout Sponge

    Shopping List

    1. TILES
    Available at home centers and tile dealers, though most high-end tile requires ordering as much as six weeks in advance. Tiles are sold by the square foot, ranging in price from $2 to about $50. You should look for tiles with a foot-traffic rating of 3 or above (on a scale of 1 to 5). Given a set of measurements, some tile dealers will calculate how much you need, and art-tile manufacturers may make you all the tiles, in the right sizes, to order. But you can also determine the square footage yourself: Multiply the length in inches by the width, and divide the result by 144. Then add 10 percent to that number for waste cuts.

    2. ½-INCH CEMENT OR FIBER-CEMENT BACKER BOARD
    to go over a plywood subfloor and create a flat, stable surface for installation.

    3. CONSTRUCTION ADHESIVE
    to glue backer board to the subfloor.

    4. 11/4-INCH BACKER-BOARD SCREWS
    to screw the backer board to the subfloor. 5. UNMIXED THINSET MORTAR
    Also known as setting cement. One 50-pound bag should be enough. Do not use mastic; it can’t take high heat.

    6. LATEX ADDITIVE
    to mix with the thinset, as the liquid. It improves flexibility and creates a stronger bond than a water-based mix.

    7. TILE SPACERS
    Porcelain tiles can have as little as a 1/8-inch gap between them, while ceramic tiles can be 3/6 to 3/8 inch apart and terra-cotta tiles can be spaced 3/4 inch apart. Handmade tiles may require special surface spacers that accommodate irregularities on the top edge. Buy spacers appropriate for your tile type and the grout lines your layout dictates.

    8. GROUT
    Use sanded grout if the space between your tiles will be greater than 1/8 inch, unsanded if it’s smaller. You can also buy colored grout to more closely match your tile.