Because a hearth is in front of a major focal point, you want it to appear symmetrical. If you're working with high-end art tile, you're in luck: Manufacturers or dealers will often create a layout for you and order the proper amount of materials in sizes that require a minimum of cutting. But more often, you'll need to play around a bit with placement and pattern to make sure tiles look even, neat, and aesthetically pleasing.

Before the final design is put in place, however, the structure needs to be sound, because a hearth receives constant abuse. A lot of that starts with the substrate, which should be even and level. "Just like any good construction, if the foundation is true, the rest will follow," says tile contractor Joe Ferrante, who has worked on several This Old House TV projects. If the area has a concrete slab, you may need to smooth it out with a skim coat of thinset after removing the old hearth. Newer houses, on the other hand, may have a plywood subfloor under the old tiles. To create a noncombustible substrate for the tiles, you'll need to put down a piece of cementitious backer board. You'll also have to bring the hearth dimensions up to code: Most ­localities require hearths to be 16 inches deep and extend 8 inches beyond both sides of the firebox.

Once you have a good base for the tiles, it's important to adhere them to the substrate with thinset, not tile mastic, which can't hold up to the heat of a fireplace. But before you put the tile down, take the time to perfect a dry-laid version of your design. Try different configurations and patterns—a 3-by-6-inch subway tile, for example, lends itself to a bricklike running bond, but simple square tiles might look best in a grid—and make sure everything fits well, with even lines. "There's no such thing as checking too much," says Ferrante. Then, as you set the tile, work slowly and deliberately to stick to your design.

Tiling can seem daunting, but the great thing about a hearth is that it's essentially a flat rectangle. You have room to play around—with different borders, with different patterns. And the best part is that thinset is very forgiving. As long as it's wet, you can always pull up a tile and redo your work, making sure that all the puzzle pieces fit together perfectly.
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    More in Painting & Finishes

    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.

    to go over a plywood subfloor and create a flat, stable surface for installation.

    to glue backer board to the subfloor.

    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.

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

    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.