Sunday, March 18, 2012

How do you get rid of black mold on shower grout and caulk in the shower?

How do you get rid of black mold on shower grout and caulk in the shower?

By: Handy Andy

There are folks out there that say that if they have mild cases of either type (surface, not entrenched), they use Tilex and let it sit. They believe that it if it's mild, you should be able to walk away, come back in about 30 minutes and it should be gone. That is optically true.
If it's caulk and it's entrenched, replace the caulk. There is a certain point where it's deep in the stuff and no voodoo will get it out.
The real problem is twofold - the grout may not be sealed properly and you may not have adequate air ventilation.  Grout Sealer can be used when the grout is completely dry - you really should wait 5 days after cleaning it. Preferably after you have been out of town, not using the area. Get Aquamix Gold or equivalent and a cheap sponge paint applicator. Check the air ventilation.
We always like to recommend that if you take a shower, to turn your bathroom ventilation on.
If your grout keeps molding after it's been cleaned and sealed, the problem is probably in the wall. Someone took too long to address the issue. It's one of the issues with grout, as grout is a very porous joint, and unless you stay up on the maintenance, some of them will fail, and moisture will be sucked into the sheet rock or plaster, or even hardiboard. To get rid of the problem you will either need to replace the sub wall and retile.
Now, what to do about a shower that has not been maintained in the above manner since it was new?
Use cleaners that do not contain acids (this includes vinegar). Acids remove desirable material. It is recommended to an alkaline cleaner to remove built-up soap scum and mineral deposits. Use this cleaner only when heavy build-up is present. It should not to be used as a daily cleaner. For routine maintenance use a pH neutral cleaner. Both products are available at tile supply stores or at Lowes and Home Depot.
You should also seal the grout and tiles with a penetrating tile sealer both when the shower is new and periodically through the years. Grout and ceramic wall tiles are not waterproof and will absorb quantities of water as the shower is used. Water is the element necessary for breeding mold and mildew.
There are many brands of tile sealers, all of which fall into two general categories: mineral based and latex or acrylic based. Use the latex based products. They won’t stink up your house like the mineral based ones will. If you buy your products (cleaners and sealers) at full line tile supply stores, you’ll have the best chance of obtaining the very best products available. The people who work at these businesses are much more knowledgeable about tile products than people who work at the local home centers.
Sealers do not last forever. I would certainly go for the product that will last the longest. In the past, sealers were only good for a year at most. I like Impregnator 511 from Miracle Sealants. Both are available at Home Depot.
Sealing a shower is relatively easy. Make sure the shower is completely dry. Dry means, it usually takes about five days for the moisture to evaporate from behind the tiles. The five days applies to all showers built with lath and mortar whether new or old. If your shower has only sheetrock behind the tile, the walls will usually dry in two days (unless the sheetrock is saturated, in which case you have problems that can’t be fixed with sealer). Shower floors can take weeks or months to dry out after having been in use for a period of time. You might want to forgo sealing the floor in that case. In new showers, the floor can be sealed along with the walls, but never use an old fashioned sealer on a shower floor. The floor needs to breathe.
If your shower is tiled with large floor tiles which are dense to the point that they won’t accept sealer, you should use a small piece of sponge to apply sealer to the joints only. Wipe the edges of the tiles with a damp cloth. It is important to understand that not all floor tiles are super dense. Some of tile will accept the sealer. Do a little test. Dap sealer on a tile and notice whether the tile absorbs any of it. It does, seal the tiles and grout. If no sealer is absorbed by the tile, seal the joints only.
It is imperative that you remove all sealer from tile surfaces before it has a chance to dry. Some of the water-base sealers are not “strippable” after they’ve dried. Pay attention.
Here is the recap: Clean it, seal it, and wipe it down each time it’s used.
You trusted handyman Handy Andy
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March 2012


  1. Thanks for addressing this topic. Helped me to understand ways to fix the mold in my shower

  2. If you’re in doubt of any unpleasant growth in your house, you should simply assume there is a problem whenever you see mold or smell mold odors. Testing should never take the place of visual inspection (which is recommended) and it should never use up resources that are needed to correct moisture problems and remove visible growth.
    People used to think that molds were harmless but it isn’t. The fact is, some molds produce a toxin called aflatoxin (toxic and among the most carcinogenic substances known) that causes illness and death in people.
    Sometimes, mold growth is hidden and difficult or hard to locate and find. In such cases, carefully conducted sampling and visual inspection may help determine the location of contamination. However, mold testing is rarely useful for trying to answer questions or inquiries about health concerns. For more information, see mold testing services

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