How to Tile a Hearth

Why is it that the mantel always gets all the attention? Sure, it flaunts the grand shelf, the carved legs—it’s the frame around the flames. But mantels come and go. It’s the hearth that’s always been there, an ornate buffer between the fire and the shag rug, descendant of the glazed bricks used by ancient Babylonians to decorate the foot of the fire.

So now that you’ve pulled up that shag in favor of some new hardwood, think about upgrading the fireplace as well. Ditch the worn and scratched masonry pad that’s been in front of it for decades and jazz things up with some colorful new tiles. As This Old House technical editor Mark Powers shows on the following pages, you can change the whole look of a fireplace—and the room—in one or two weekends. Then, when you’re finished, you’ll be able to truly say that the hearth, ahem, goes on.

Field tile in Rothwell Gray, from Motawi Tile, about $108 per square foot.

Step 1

Overview

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.

Step 2

Prepare the substrate

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.

Step 3

Dry-fit the tile

Measure the firebox opening behind the hearth and determine its center point. Extend that location to the hearth and draw a line on the substrate, bisecting it. If the center is close to an obvious mortar line or other focal point on the firebox, draw the bisecting line at that point. Then find the center of the hearth front to back and draw another line through it perpendicular to the first, so that the hearth is divided into quadrants.

Starting at the front edge of the hearth, dry-lay a line of tiles in one of the quadrants, beginning at the center line and moving out to the edge. Make sure to leave space between the tiles to account for grout. Mark edge tiles that need to be cut. If any cuts would create a tile less than 1 inch, cheat the grout lines to absorb this measurement rather than use a tile sliver.

Continue filling in the quadrant until you reach the center line front to back, following the pattern you’ve determined you want for the layout. If the tiles at the center extend above the line, mark a new reference line along their edge.

Dry-lay tiles in this manner until you fill the the whole hearth area. Mark tiles at the back edge for cuts, if necessary.

Tip: Once you have a satisfying layout, transfer all the tiles, in order, to a board to keep track of where they go.

Step 4

Cut the tiles

Align the cut mark with the tile saw’s blade. Adjust the fence so you can press the tile securely against it with the mark and blade in line. Wearing eye and ear protection, turn on the saw’s blade and the water supply. With the tile against the fence and water flowing over the blade, slowly feed the tile into the blade with light pressure.

Step 5

Spread the thinset

In a clean bucket, combine dry thinset with latex additive, following the proportions on the packaging. Using a drill/driver fitted with a mixing paddle, slowly combine the ingredients until the mix is thick enough to stick to a trowel turned upside down.

Using the straight edge of the trowel, spread a layer of thinset into one quadrant of the substrate, making sure you can still see your layout lines. Turn the trowel around to the notched side, and holding it at an angle, scrape ridges into the thinset.

Step 6

Set the tile

Set a tile at the intersection of the layout lines, giving it a slight twist as you embed it into the thinset. Continue working outward from the center toward the edges, placing tiles according to the layout you determined earlier.

Tip:Test the thinset mix by pulling up a tile and turning it over; the ridges should spread and stick to the back of the tile without being too soupy.

Step 7

Fill out the field

Set the rest of the field tiles, one quadrant at a time. Work outward from the center, and fill in the entire field before adding the cut tiles at the edges. Use spacers between the tiles to maintain even gaps for the grout.

Once you’ve completed a quadrant, check the tiles with a level or straightedge. Make sure the pieces are set on an even plane. If a tile is too low, pry it up and butter the back with thinset to raise it. If a tile is too high, gently push it down or remove some mortar to create room. Fill in the edge tiles last and make sure all grout spaces look even and straight.

Tip: Once spread out, thinset has a working time of about 30 minutes, so only cover small areas at one time

Step 8

Grout the joints

Using a grout sponge and/or a putty knife, clean out any joints where the thinset has squeezed out. Once the tiles are set, clean, and evenly spaced, leave the thinset to dry for 24 hours. Remove the spacers.

Following the directions on the packaging, mix the grout with water until it resembles peanut butter. Using a grout float held at at angle, spread a layer of grout diagonally across the joints, pushing the mix between the tiles. Work the float in all directions to ensure all the joints are full; never sweep it parallel to the joints or it will catch in the gaps and pull up the mix. Do not grout the joint around the edge of the hearth.

Once the joints are well packed, turn the float on edge and, again sweeping diagonally across the joints, scrape off the excess grout. Let the grout dry about 30 to 60 minutes, until firm to the touch.

Dampen a grout sponge and squeeze out the excess water. Wipe the surface of the tiles in a circular motion to clean off the excess grout. Once the tiles look fairly clean, leave the grout to dry overnight, until a thin haze covers the tiles. Then, using a clean, dry rag, buff off the haze.

Fill the joint around the perimeter of the hearth with caulk that matches the grout. Smooth the caulk with a wet finger. Allow the hearth to set for another two or three days before building a fire.