Mold on Marble Shower

Updated: Mar 7

Constant water infiltration under the tiles causes mold on marble shower and damages the most durable marble. Here’s what to do about it.


When you first see the tell-tale signs of mildew stain, or mold on your marble shower, you may think the problem is with whoever is cleaning it. So, you Google “what gets rid of mold and mildew in showers” or talk to your cleaning staff. Maybe a different cleaning solution, tools, or frequency will stop the problem.


But that scaly white mildew, or scary black mold keeps coming back! Whether on the surface panels or (more likely) attacking the grout, this living organism is persistent.

Marble shower with discoloration, stains and mold

What causes mold and mildew on marble shower and grout?


Marble—much like any natural stone or porcelain—is a beautiful and durable surface. It’s a good choice for showers, when properly protected and regularly maintained. But even with the best installation and finest marble:


Natural stone, porcelain or marble showers are not water-resistant.

Yes, showers are built to be waterproof (it’s required by building code), but they are not water-resistant at every moving part or joint. That’s what allows water to sneak in under the tiles. Add to that the repeated water, soaps and oils, cleansers and sponges, and natural settling, and you can see how water can find its way below your stone.


It’s that constant water infiltration under the tiles that causes mold on marble showers.


And, unfortunately, when you see it, or smell that mildew odor, it’s probably the tip of the iceberg. That’s why it’s so important to correct it early.


How to Spot Marble Shower Leaks and Problems


Having worked on thousands of showers over the years, we’ve compiled a list of the most common problems that are RED FLAGS. Signs that you should check your marble, natural stone or porcelain shower include:

  • Grout or marble discoloration

  • Mildew Stains

  • Broken or missing grout

  • Micro-fissures on grout

  • Cracks on marble

  • Loose tiles

  • Efflorescence or calcium buildup

  • Persistent mold or mildew

  • Musty smell

  • Missing plumbing fixture sealants

  • Missing or damaged silicone around a glass enclosure

  • Worn out plastic seal strips around the glass enclosure

  • Leaks outside the shower's protective liner

  • Paint bubbling outside the shower, near glass enclosure

  • Loose tiles outside the shower threshold

Please NOTE: If you suspect leaks in your showers consult first with your trusted plumbing professional to diagnose and rule out slow pipe leaks behind the shower walls.

Mold on marble shower

How NOT to solve the problem


First, save your energy and money; don’t try to resolve these problems by replacing the materials. Don’t turn to harsh chemicals, that are likely to work only temporarily, and on the surface.


And never use harsh cleaning products, acidic cleaners or vinegar to clean! They’ll only erode the grout and etch the marble surface, making your problems worse. See our surface care recommendations for marble and porcelain


Plus, you must be aware that traditional simple grout repairs, caulking application and/or repairs, surface coatings or sealers will not resolve or prevent water infiltration under the tiles that lead to saturation. The type of saturation we call Waterlogged Shower™ -- and that later unfolds into the red flags above!


The truth is, while these challenges with marble and stone showers aren’t new, there are newer, more modern ways to solve them.


Stone experts have historically advised homeowners that upkeep will mean:

  • Applying sealer to the showers as often as possible;

  • Squeegeeing the water off the surface;

  • Keeping the shower dry once you’re finished in it.

This classic route to preserving your luxury shower adds up to many hours of labor!

Labor that, from our experience, is not necessary when showers are repaired and protected properly using a unique preservation process from TERSO MR®. With this approach, all you need to do is seal every two years.


The Modern Approach to Marble Shower Protection


When you see any of the signs above, the solution is to correct the problems at their root—and fortunately it can be done without any construction or major disruption to your life. Here are the 5 key steps:

  1. Dry/extract the water that has infiltrated.

  2. Inject premium epoxy to stabilize the structural shower movements.

  3. Remove/replace all damaged grout.

  4. Purify the stone or porcelain surface.

  5. Apply premium impregnating sealer.

Note that if your shower has a glass enclosure, it is vital to inspect glass perimeters for damaged silicon and worn-out plastic seal strips. Those areas can also contribute to water infiltration and leaks outside the shower's protective liner.

Mold on marble shower

We can’t stress it enough: in order to prevent mold and mildew from returning to your shower, the water infiltration problem needs to be permanently addressed from the source. That means drawing out the constant water, moisture, and impurities trapped under the tiles, followed by proper specialized repairs.


Our Preserve Solution System offers the most cost-effective approach to stone shower maintenance, purifying and applying sealer every two years to preserve the shower's surface and integrity.


Our advice is, use any stone material you desire for your luxury showers, and it will stand the test of time as long as no water infiltrates under the materials through the joints or fissures. Mold and mildew on marble shower doesn’t have to be a problem for you; just be sure to choose TERSO MR® to help protect and repair yours. Contact us to discuss your marble shower.


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