Adhesive holds tiles in place on floors, walls and countertops. But without grout to fill and seal the seams, they won’t stay there for long. It’s the crucial finishing step on any tile installation — a straightforward job needing only basic tools and skills, though knee pads might be welcome if you’re working on a floor.
Types
The many varieties include dense epoxies, fine Portland cement mixes for wall seams and sanded grouts for wider joints on ceramic floor tile. Selecting one isn’t hard because tile manufacturers specify not only the preferred type of adhesive but also the right grout for their products. It’s up to you to mix it properly (most come in powder form and mix with water) and to tint with dry colorant if you can’t find a stock color that suits. (Bear in mind, while lighter-colored grouts can accentuate an interesting tile pattern, darker grouts are better for hiding dirt.)
But there are also prepared grouts made by companies such as Savogran and UGL labeled Ready Mix Tile Grout — typically a fast-drying acrylic-latex mixture that sells for about $10 a quart. UGL says its mildew-resistant prepared mix can be used on ceramic and mosaic tile, and it sets fast enough to withstand water after 24 hours.
Mixing
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Most grout comes as a very fine powder that seems to require more water than the manufacturer specifies. More makes it easier to mix and to spread, but an overly soupy consistency weakens the mix by over-diluting the Portland cement. The mix may sag in the joints and, even hours later, damp wiping to remove the grout haze may also remove some grout. The key word is workable — a grout mix just dense enough to clump in your hands but still spreadable with a rubber float that forces it into the joints.
Spreading
Remove any spacers or debris in the seams, including excess adhesive that has bulged up into the joint. For maximum strength, grout should completely fill the spaces between tiles. Then use either a sponge float or squeegee to work grout back and forth across the joints at a 45-degree angle. This keeps the tool floating on the tile surface instead of gouging into the seams. After several passes, you’ll see the seams fill and can move on to another area. To make final cleaning easier, trowel excess grout off the surface.
Cleaning the haze
As grout hardens it leaves a hazy residue on the tile surface. After allowing the grout to set (check the manufacturer’s instructions), you simply wipe it away. Use a big, soft sponge, dampened but not dripping with clean water, ringing out the excess grout residue and changing the water frequently. After a few passes the haze will dry again, but lighter this time, and again next time. When the surface looks clean, even dry, declare victory and make one final pass with the damp sponge or a cheesecloth pad.
Sealing
Few manufacturers mention that most grout, like most masonry, is porous. Mold will grow on it, dirt will cling to it and stains will embed in it. Scouring the joints back down on your knees next to the toilet is no fun. So consider one extra step, after the grout is cured, to seal its surface. The material of choice, liquid silicone, would make the tile surfaces as slippery as ice. It has to be applied to the grout only. To do that, use a liquid silicone applicator — a small bottle or even an artist’s brush.