Grout can turn a good-looking tile job into a bad one. No matter how grout is applied, problems can crop up. Fortunately common grout problems are usually easy to fix. Anyone with solid do it yourself experience will be able to tackle this task. In each step listed, there will be a cause and a solution to common grout problems.
Fix minor grout cracks. Grout cracks are the most common problem. House settlement or improper underlayment installation usually cause small grout cracks. Minor cracks can be fixed by this process. Run a 1/4-inch wide bead of latex caulk across the entire crack. With your finger push the caulking into the crack. Wipe any extra off the tile with a wet sponge. Sprinkle dry grout onto the caulked area. Use a finger to rub this in. Drip water on the area and blend. With this method if the tile moves again the caulk will stretch to help hide the crack.
Fix major grout cracks. Grout cracks caused by improper tile installation or a loose subfloor. They are often found around loose or hollow tiles. Tapping a broomstick onto the tile tells if the tile has a hollow spot in the setting material. You must remove loose or hollow tiles and fix the installation or subfloor problem. Then replace the tile and re-grout.
Fix low grout. Low grout spots are created when the installer wipes to much grout out of the grout joint during installation. To fix, wet the grout with clean water and re-grout, blending the new grout into the old. Wet grout bonds with new grout better than dry will.
Fix powdery grout. Soft powdery grout is caused when the installer does not use enough water when mixing the grout. The only solution is to use a grout saw or knife and remove the problem grout. Re-grout these areas with properly mixed grout.
Fix pinholes. Grout with pinholes is caused when the installer uses soupy grout. Too much water was used during mixing or the installer left too much water on the joints while wiping. As the grout dried the water evaporated leaving holes. The solution here is to dampen the holes with water and push grout into the holes with a finger. Wipe off extra grout with a damp sponge.
Fix discolored grout. New grout that is discolored with dark or dirty looking spots, is caused when the installer added too much water to the grout and then let it sit in the bucket to thicken up. The colorant separated and clumped together, creating uneven color. There are two solutions. The first is to remove bad grout and re-grout using a grout saw. The second is to use a grout stain to even the color. This usually means you have to paint all of the grout.
Fix two different colors. If a tile was repaired and the wrong color grout was used you can do one of the following. Remove the wrong color and replace with the new one, blend the new one into the old one, or stain the new grout the right color
Clean dirty grout. Dirty sanded grout that has not been stained can be cleaned with white vinegar and a stiff bristle brush.