Renewing Bathroom Grout

No matter how beautiful your tile is, if the grout is in bad shape it can make your bathroom look like it belongs in a 1950s motel. Most of the time, killing mildew and resealing the grout will cure the problem. But if the mildew persists or the grout is really shot, it's time to repair the grout. Happily, the task is almost fun, and the tools are inexpensive and simple to use.

Attack the mildew first: bathrooms are veritable petri dishes for growing this ugly stuff. Many household products are specifically designed to kill mildew, so choose a tile cleaner with mild chlorine bleach or phosphoric compounds. Don't use full-strength bleaches, however; they can actually damage the grout. But whatever you use, be sure to wear rubber gloves and always scrub the cleaning solution away from your eyes. A sponge with a scrubbing strip is best for this job.

If you have grout that's discolored but otherwise intact, you can often restore it with a grout colorant. In addition to brightening the grout, it helps seal against water, mold, mildew and stains. Grout colorant doesn't scrub off, and you can use it on large areas or for small touch-ups. After thoroughly cleaning and drying the grout, apply the grout colorant according to the directions on the package.

Even after your grout is mildew-free, it still may not be a pretty sight if it has succumbed to the ravages of time and moisture. Grout that's hopelessly stained, crumbling or missing between tiles not only looks bad, it can allow water, dirt and debris to accumulate and even damage the tile substrate. At this stage, bleaching and recoloring isn't an option. Regrouting is the only way to make your tile look new again. Another reason to regrout is to change to a different grout color.

Before you replace damaged grout, a little investigation is in order. Cracked or crumbling grout often indicates that the substrate has cracked, shrunk or moved. Discolored or spongy grout may be evidence of a water leak inside a wall or shower pan. Regrouting the tile without fixing the underlying problem is only a temporary solution.

Once you determine that regrouting is in order, how you handle it depends on how extensive the job is. If you're just repairing a small area and the existing grout is clean, you can press fresh grout into cracks and voids with your fingers.

If damage is extensive say an entire floor with eroded or badly discolored grout you must remove the old grout. Be forewarned: this can be a difficult job, as the old grout must be completely removed down to the substrate. And if your floor has narrow (1/16 inch) grout lines, you'll need to work carefully or you may chip tiles in the process.

Step by Step

1. Remove the old grout. Remove the grout with a grout saw a hand tool with a short, offset blade specifically designed to cut down into the narrow space between tiles. After sawing down all the grout lines, use a chisel or utility knife to gently remove any remaining grout from the edges of the tiles. Then vacuum up all the grit and any stray chunks of grout. This is the time to replace any damaged tiles.

To prepare the tile for the new grout, scrub down the tile surface with a product designed for cleaning dirt and soap scum from tile (such as Homax Grout and Tile Cleaner) or with a solution of 10 or 20 percent muriatic acid diluted in water (be sure to mix the acid into the water, not the other way around it can splatter). Remove any plumbing fixtures, electrical plates and the like that you don't want to get grout or muriactic acid on. (Muriatic acid can etch metal.) Protect porcelain fixtures and wood trim on adjacent surfaces with masking tape. And while you're at it, protect yourself as well. Muriatic acid is nasty stuff: wear heavy rubber gloves, goggles and a long-sleeve shirt. Always brush or sponge away from yourself and if you get any on your skin, get that skin under running water fast. Finally, clean out all the grout lines with a brush and a shop vacuum.

2. Apply new grout. You can buy smooth grout and sanded grout as dry powders, ready to mix with water (follow the directions on the package). Smooth grout also comes premixed in plastic tubs, ready to color with universal tints. Whether you're using sanded or smooth grout, choose a mix that's "latex modified"; it will be water resistant and less likely to crack.

If you're replacing all the grout, you can make it any color you like. But for spot repairs, you'll have to match the color of the old grout. If there's a tile supply near you, borrow their sample grout card, compare it to your grout and select the color that's the closest match. To assure a good color and shade match, mix up a sample batch of grout, apply it to a small area and wait for it to dry thoroughly (usually three or four days) before evaluating the match any dampness in the grout alters its hue.

If you mix your own grout, add just enough clean water to make the grout firm and spreadable not stiff. After stirring thoroughly, let the grout set up for about 10 minutes before stirring it one more time, to get any remaining lumps out.

Pour a small amount of grout on the tile and spread it with a grout float, a rubber-faced trowel. Tilt the face of the float at about 30 degrees as you spread the grout. Once the grout is evenly spread, use the grout float to press and pack the grout into the joints between tiles. When you feel resistance, which indicates that the joints are filled, run the float with its face at a right angle to the surface diagonally across the tiles to remove excess grout. Pour out another pile of grout and repeat the process on an adjacent area.

After you've covered 10 to 20 square feet, check to see how dry the grout is. It's best to clean off the excess grout when it's firm but not completely dry. This may take anywhere from 5 to 20 minutes. Use a large, round-cornered sponge dipped in a bucket of clean water and wrung out thoroughly, working with a circular motion. The idea is to remove the grout from the tile surface without removing too much from the joints. Rinse the sponge often, and always wring it out before you proceed. For the final cleaning, take slow, short passes at right angles across the tiles, moving the sponge very carefully to leave clean and even grout lines. Wait 15 to 20 minutes, then wipe off any remaining haze with a soft, clean cloth. Any bits of grout that you miss may harden overnight, but you can get them off with a plastic abrasive pad and scouring powder.

3. Seal the grout. Let the new grout cure for at least three days before you seal it. Don't rush this step unless you want to deal with badly stained grout again. A good quality grout sealer, such as TileLab penetrating sealer, is expensive (about $25 a pint), but well worth it. Apply the sealer according the manufacturer's directions. Then, stand back and admire your beautifully renovated tile!