Grout Fix for a Good-as-New Tile Floor

To increase the chances of a successful repair, get rid of as much of the old grout as possible.
To increase the chances of a successful repair, get rid of as much of the old grout as possible. (By Tim Carter -- Tribune Media Services)
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By Tim Carter
Saturday, December 6, 2008

Q: DEAR TIM: The grout in one joint of my floor tile has come out. Do you know why this happened? I can see that the previous homeowner repaired it. What's the best way to work with floor grout in this situation? What type of grout do I install, and how do I match the color perfectly? -- Valerie P., Tampa

A: DEAR VALERIE: Floor grout can fail for a host of reasons. Some of them have nothing to do with the original installation, and others have everything to do with the installer or bad grout. Let's just hope that your failure is limited to this one area and that all the remaining grout stays put for a while.

Here are a few reasons why the grout could have failed: It could have been a structural failure in which the floor moved. Or the culprit may have been seasonal movement of a wood-floor system. The installer might have mixed too much water with the grout or used too much water at that spot of the floor when dressing the joint. Or the grout itself could have been bad.

To increase your chances of a repair that lasts, carefully chisel out as much of the grout as possible. Doing this ensures that the good grout you will install will not rest on top of poor-quality grout. I liken this to building a house on a foundation -- you want that foundation to be solid and stable.

You can use a small, motorized rotary tool that has a grinding wheel for this task. You can also do it with a light hammer and a narrow chisel or an old, worn-out flat-head screwdriver. Always chip away from where the grout is still solid. This puts less stress on the tiles on either side of the grout joint. Be careful that you don't strike the tile or aim the chipping tool toward the tile.

Vacuum all powdered grout and grout chunks from the joint. Use an old paintbrush to dust out the joint. The bottom of the joint and sides of the tile need to be dust-free to get the best bond between the new grout and the tile.

Matching the grout color is not hard, but many tile installers and homeowners make a critical mistake here. You must restore the existing grout to its original color and allow it to dry before you attempt to select a color. Remember, there are different shades of white and gray grouts. You can get color charts or sample grout sticks from the specialty tile store. Bring them home, and compare them under good light to get a match.

The easiest way to clean floor tile grout is to use oxygen bleach. This non-toxic powder mixes with water to make a solution that attacks dirt and food stains without harming the tile, the grout or the pigments in the grout. Oxygen bleach has no odor, and if the solution sits on the grout for 30 minutes, minimal scrubbing is needed to make the grout look as it did the day it was installed.

Stores that sell ceramic tile or tile and stone products almost always have a wide selection of grout colors. You will probably be using sanded grout if the joints between your tiles are wider than 1/8 inch. Look closely at your existing grout. If it has a rough texture similar to medium-grit sandpaper, you have sanded floor grout.

Mix some new grout, about a cupful, to the consistency of thick mashed potatoes. Spread it out on a piece of aluminum foil so it's 1/4 inch thick. Allow this to dry in the air for two days. Crack off small pieces and set them next to the existing grout or in the empty grout joint to see how the color looks. Do this until you get a match. You may have to blend different grouts to get a perfect match.

Tim Carter can be contacted via his Web site,

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