One of our friends asks about cleaning some really stained tile grout in their kitchen. It seems that over the years the grout has just got darker and darker. Its not a small area it is most of the kitchen that has the problem so it is most likely due to dirt buildup and not mold.
If the problem is in one general location such as near a sink or outside door or in the case of a bathroom around a fixture and you see a lot of black mold then the mold might be growing behind the tile and coming through from the drywall or flooring. If you see this problem along with loose or moving tile then you will need to take further precautions and expect that you do have a mold problem.
If the discoloration is in front of the pantry or refrigerator or stove or along a pathway where you normally walk then it might just be dirt that you need to clean.
Light or surface mold is also a situation that you will run into and this is easily cured by cleaning the tile with bleach. You should allow the bleach to stand wet at least 15 minutes but if it is going to work it should remove the mold within an hour. Rinse and wash with soap and you can neutralize the bleach with a small amount of vinegar. Don’t spray vinegar directly on bleach that has not been rinsed with water as it can cause a harmful gas that can irritate your lungs and eyes.
Once the grout is clean you can seal it with a spray grout sealer. Follow the directions as to how long you have to wait before using the area and apply it when the grout is dry. Remember to clean the residual sealer as it can be slippery.
If the grout can not be cleaned you can remove it with a grout saw which is a small tool that looks like a hacksaw blade and fits between your tile to remove the grout. You will then have to regrout. If you have to replace your grout you should do a large area of it. For showers do a full wall to a corner at least. For floors you may need to do the full floor. You can test an area before you decide to do a larger area and there are grout matching swatches at your home store to help you match your original color. However even if you buy the exact same grout you most likely will have variation in the color. It is your choice how far you go with replacing the grout but dramatic changes in colors do mean larger areas need to be replaced and then sealed.
Final Note
If you do find mold that you can not remove and maybe loose tiles you will have to do some repairs by removing the tile and probably the backer board or drywall and in the case of the floor you might end up pulling up your subfloor.
Once mold gets this bad you are really talking about a major repair. Replacing just a handful of tiles in the effected area won’t help for long.
You will also have to find the problem that caused the mold. It could be from grout failure allowing water into the materials behind the tile or it could be moisture in the wall or floor.