Fireplace hearths have the dual function of protecting the surrounding floor area from heat damage, and making the fireplace an attractive addition to the home—this is best done with tile, which fulfils the two functions admirably. While tiling a fireplace hearth may seem like a job best left to professionals, with a little patience and know-how, it is not something that an avid DIYer should shy away from.
Check the substrate material. For wood, cut a hearth-sized section of backerboard with the utility knife, glue it in place with construction adhesive, then screw it down with non-corrosive screws, one every eight inches, on centre. Fill screw holes with thin set, and scrape flat with the trowel. For concrete, fill any depressions with thin set, scraping flat with the trowel; let dry.
Find the centre of your firebox, then rule a chalk line, dividing the hearth in two. Divide the hearth length, and rule a line, which will dissect the first line, creating four sections on the hearth. Dry-fit the tiles, spacing with tile spacers. Begin with the inner cross section, and work your way outwards, if any tiles need to be cut, mark them along the cutline with chalk.
Transfer the dry-fit design to the floor besides the hearth, keeping the design exact.
Put on your goggles and dust mask, then feed the tiles needing to be cut through the blade of the wet saw, applying even, firm pressure. Don’t try to force the tiles through.
Apply a small, 1/8 inch thick layer of thin set to the inner section of the hearth, furrowing the thin set with the notched edge of the trowel. Press in your tiles, putting in the tile spacers and gently tapping them into the thin set. Check that they are all level. Fill one section of your hearth at a time in this manner with thin set and tiles, checking with the level as you go—tiles too high can be pressed down into the thin set; tiles too low need a little more thin set under them. Let cure for 24 hours.
Mix the grout as per the manufacturer’s instructions. Take out the tile spacers. Spread the grout, working it into the spaces between the tiles at a 45 degree angle across the tile lines. Once the whole hearth is grouted, wipe away the excess with the sponge. Let cure for 24 hours.
Give the hearth a good wiping with the sponge, then allow it to cure for three days before lighting a fire in your fireplace.