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Tile Grout

The Purpose of Grout

When grout does its job — locking tiles tight, keeping out water, and giving floors and walls a finished look — nobody pays much attention. It's only when grout fails, becoming stained, cracked, or falling out altogether, that people take notice.

But grout deserves more respect. "Not only does grout fill the voids, it makes the floor, wall, or countertop stronger by bonding the tiles together and preventing the edges of a tile from chipping and cracking," says David Goodman, the tile contractor for This Old House's Nantucket project.

Here’s everything you need to know about grout: from the different types, sealing and color options and ways to repair.

Cement-based Grout

Grout comes in two basic types, and the choice of which one to use depends not on the tiles but on the width of the joints between them. Narrow joints of 1/8 inch or less call for unsanded grout, a pudding-smooth blend of Portland cement and powdered pigments mixed with water. Joints wider than 1/8 inch get sanded grout — the same material, but with sand added. The sand helps bulk up the grout and keeps it from shrinking in the joints.

Three decades ago, when he started in the business, Goodman says, "we'd just add powdered grout to a bucket of water and away we'd go." But older cement-based grout was brittle and prone to cracking. It also dried irregularly, leaving colors inconsistent. Today's grouts use polymer additives, which ensure color quality and increased flexibility, allowing for joint widths of up to 1 1/4 inches. Those wide joints come in handy for camouflaging irregularities in handmade tiles and for bridging the varying thicknesses of tile in some patterned installations.

Despite their improved performance, however, all cementitious grouts are porous and subject to staining. That's why manufacturers and installers recommend sealing grout after it has cured for a couple of days and is completely dry.

Grout Sealers

Grout sealers come in two varieties: membrane-forming and penetrating. The first type is prone to peeling or getting cloudy when residual moisture from mastic or underlayments pushes to the surface of the tile. Penetrating sealers, which still breathe after soaking into tile and grout, are preferable.

Goodman sometimes invites customers to save on labor costs by sealing the grout themselves. "I give them some cotton swabs or a disposable brush, along with a can of sealer, and make them promise me they'll finish the job."

Epoxy Grout
Epoxy grout is more expensive and more difficult to apply, but its durability makes it a good choice for high-traffic areas.
Photo by John Lawton

Epoxy Grout

There are some settings — notably those exposed to acids and greases — in which even an additive-enhanced, sealed grout falls short. Such harsh conditions call for epoxy grout. Made up of two parts, resin and hardener, epoxy grout comes in both sanded and unsanded varieties and is impervious to most chemicals and stains. Early epoxies were unforgiving and difficult to apply, and had just a 45-minute pot life. This made them fast to cure but slow to be embraced by many tile setters, and anathema to beginners.

The new generation of epoxies contain detergents in the hardeners, which make for quick cleanup with water and improve workability. Because epoxy can discolor porous surfaces, such as unglazed quarry tiles or limestone, these should be sealed before grouting. But its stain resistance, hardness, and durability make epoxy grout the best choice for showers, kitchen counters, backsplashes, floors, and other heavy-traffic areas.

Is Epoxy Grout More Expensive?

Yes, epoxy grout is more expensive — as much as $8 per pound, compared with $1 to $2 for cement-based grout — but there is an upside to the cost difference: Powdered Portland cement grouts have a shelf life of only one year, while two-part liquid epoxies, if they are not subjected to freezing temperatures, will last forever in their sealed containers.

Grout Colors
Choosing very different tile and grout colors can provide a striking contrast.
Photo by John Lawton

Grout Colors

When it comes to grout color, there are three approaches: contrasting (say, white grout with black tile), harmonizing (green grout with green tile), or neutral (a shade of gray or white). While it can be tempting to go with an eye-popping combination, David Goodman tries to steer his clients toward the neutral option. "You may not be madly in love with gray," he says, "but chances are you won't hate it, either."

If you do choose a bold color, grout up a sample section of tile on plywood and live with it for a few days. "I tell people to look at the color in lots of different lights — natural, incandescent, fluorescent," Goodman says. If you make a mistake, unsealed cementitious grout can be stained or painted after it cures (sealed or epoxy grouts will have to be removed). "However, it's a pretty tedious procedure," Goodman says, "so why not make the right choice the first time?"

Grout Cleaning
Worn and blackened, the grout on a kitchen counter and backsplash first gets a dose of powerful degreaser. “Never clean tile and grout with an oil-based soap,” Parker says. “The wax in them builds up and stains grout.”
Photo by John Lawton

Grout Cleaning Solutions

Years of food and grease stains can penetrate surfaces, leaving dark grout. In extreme cases, the only cure may be to regrout or retile, but more often than not, old grout can be renewed. All it takes is a degreasing agent, a stiff-bristle brush or commercial steam cleaner, and elbow grease. Some spot regrouting is usually necessary — a process that involves digging out and replacing cracked or crumbled areas.

Debby Parker, who does business as The Tile Lady, has been in the industry for 25 years. In several hours, she and her husband, Roger Thorp, restored the tired grout in this Sacramento, California, kitchen.

Grout Steam Cleaner
A steam cleaner brings stains to the surface, where Parker and Thorp wipe them up. Homeowners can rent steam machines, but a stiff-bristle nylon brush and a degreaser also do the trick.
Photo by John Lawton

Grout Contractor Services

Tile contractors

David Goodman

Nantucket, MA


The Tile Lady

Debbie Parker

Citrus Heights, CA


Jan MacLatchie

Artistic Tile

New York, NY



Custom Building Products

Seal Beach, CA

Our thanks to

Todd Sturm

general contractor

New York, NY