Tiling over an existing brick fireplace can create a dramatic new look or restore some natural beauty if the brick has been painted over. Choose from ceramic tile, or natural stone tile like marble, granite or slate. In many cases, skim-coating the existing brick with thinset will create a strong, smooth surface for tile installation.
Applying Tile Directly to Existing Brick
Step 1: Protect Surrounding Surfaces
Place drop cloths over the hearth and the floor. Use painter's tape to mask off adjoining walls and the mantel if it will remain in place.
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Step 2: Clean and Prepare Existing Brick
If possible, you should remove the existing mantel for easier tile installation; it can be re-installed or a new mantel added later. Use a wire brush to remove any loose mortar or brick pieces from the brick surface. Soak a rag in white vinegar and scrub any soot from the face of the fireplace. Allow the brick to dry for up to two days before proceeding. Meanwhile, measure the fireplace to determine the number of tiles and quantities of thinset and grout that you will need.
Step 3: Create a Smooth Work Surface
Mix latex-modified thinset cement in a bucket according to the manufacturer's instructions. Use a flat trowel to spread thinset over the brick, filling in the grout lines. Allow the thinset to cure. If the grout lines are still visible after the first coat has dried, apply a second coat of thinset to smooth out any dips or grooves. Allow the second coat to cure completely.
Step 4: Install a Ledger Board
A temporary ledger board will provide a useful guide for installing the tile in line with the existing fireplace opening. Align the top edge of a one-by-four board with the top of the fireplace opening and nail the board in place.
Step 5: Install Upper Tiles
Mix another batch of thinset according to the manufacturer's instructions. Apply the thinset above the 1x4 board, combing with a notched trowel. Starting at the center, set the first row of tiles above the 1x4 board, using tile spacers between the tiles to ensure even gaps. Continue tiling up the fireplace.
Step 6: Cut and Install Partial Tiles
Once you have placed all full tiles that will fit, measure the remaining space at the top or sides of the fireplace to determine the tile sizes to cut. Remember to factor in the width of the grout line. Use a tile saw to cut tiles to the correct size and then install them in place.
Step 7: Install Lower Tiles
Once the thinset has hardened, pry off the 1x4 board. Mix a batch of thinset according to the manufacturer's instructions. Comb the thinset over the bottom portion of the fireplace with a notched trowel. Install tiles from the top down. As in Step 6, measure and cut partial tiles to complete the bottom and sides. Allow the thinset to dry completely.
Step 8: Apply Grout
Mix a batch of grout according to the manufacturer's instructions. Apply grout to spaces with a grout float, holding the float at a 45 degree angle and wiping diagonally across the tiles. Pass over the grout lines a second time to wipe off excess grout and ensure that the gaps are filled completely.
Step 9: Clean off Excess Grout
Allow the grout to set for 15 to 30 minutes and fill a bucket with clean water. Use a wet grout sponge to wipe off excess grout from the surface of the tiles. Work in sections and change the water as needed. Allow the grout to dry for three hours before a final cleaning with a wet sponge.
Alternate Method Using Cement Board
Some brick fireplaces have very uneven or painted surfaces that would be difficult to smooth with thinset cement. Perhaps you even want to alter the size and shape of your fireplace surround. Installing cement board over the existing brick is a fairly simple way to create a smooth surface for new tile.
Cement board is preferable to other substrates, such as plywood, because it won't warp or rot. Unlike the thinset method, cement board surrounds can be removed without significant damage to the underlying brick. Framing may be added around the original fireplace to change the size of the surround.
There are some drawbacks to cement board, however. Cutting the board requires carbide tools and will generate silica dust, requiring goggles and a respirator for your protection. Nails or adhesive used to attach the cement board to the existing brick may loosen over time. Cement board will also add thickness to the fireplace surround, so you will need to consider how to finish the edges for a neat and fire-safe appearance.