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Meet The Sound Test: Step 1 to keep mold out of a marble shower

Want to keep mold out of marble shower and other wet areas? Prevention is key, and the Sound Test is step one of our secret weapon.


Mold on marble or stone surfaces is easy to handle with proper cleaning; preventing what lurks below the surface is another story!


Yet that’s where prevention counts the most for helping keep mold out of marble shower and other wet areas. Microscopic spores seep into grout fissures, and feed on what lies in the air pockets hidden below your tiles.


It’s not necessarily anyone’s fault. Even the most expertly installed tile can settle and create problems. Prevention is truly your best defense.


And that’s where the sound test is an invaluable first step in marble shower protection!


What is the Sound Test?


At its most basic level, a sound test is simply a controlled means of hearing where there is a change in pitch when a surface is tapped. In the case of a structural-borne sound test such as the type we use as part of marble shower protection services, we are listening for any indication that the adhesion of a marble, stone or even glass tile is loosening (or missing).

  • Higher resonance or pitch indicates that the layers beneath are thick, and secure. This is a great sound to hear, because it means that the tile, thinset*, and the flooring substrate are bonded so closely they are acting as one layer.

  • Lower resonance or pitch often sounds hollow. You’ll hear it when gaps exist in the layers. These gaps mean air pockets exist. And those pockets are what create warm, moist space for mold and mildew to grow. If you want to keep mold out of marble shower and bathroom spaces, it’s time to act!


*NOTE: Thinset is a type of mortar used to bond tile to the floor’s base layer or “substrate. ” This base layer may be cement, concrete, cement-covered backer boards or, often, waterproof membranes that cover these surfaces.


mold out of a marble shower

What causes gaps to develop in the floor or wall tile?

Oh-so-many-things can cause this… here are the top 3:


  1. Dusty tile backing: when tiles are manufactured there is a lot of dust created – dust that can settle deep into the natural nearly-invisible crevices in the stone surface. It’s possible that not ALL the dust was completely removed before the tiles were “buttered” (a.k.a. coated), with thinset mortar. Initially it may seem as though the surface is coated and adhering just fine; yet as the structure settles or floor is walked on, the dust inevitably shifts, creating microfissures that eventually grow into those gaps spores love.

  2. Thinset only applied to the substrate: sometimes this can lead to insufficient and/or inconsistent mortar material for creating the ideal degree of bonding. The best practice, both for best adhesion and to keep mold out of marble shower and other structures, is to butter the back of the tile AND the substrate, then apply the tile right away.

  3. Too much air time for thinset: thinset can only stay exposed to air for so long before a film begins to form on its surface; if this happens, it may feel like there is adhesion (because the tile seems to sink in when pressed down), but it won’t have the maximum bonding strength. Humidity and temperature in the air can both influence air time, so we always suggest being conservative, and definitely follow manufacturers’ guidelines!


What’s next to keep mold out of marble shower areas?

This is the best part! Once we find the gaps, we’re able to:

  • dry out the area,

  • remove the mold or mildew from below the shower tiles,

  • and fill the gaps with a specially-prepared liquid epoxy solution that flows in and restores (or creates) a solid bond,

  • repair grout and/or seals on marble tile surfaces.


(Still curious about water infiltration in showers and its challenges? Read this.)


As stone expert Vincent Carramusa says “This technique has revolutionized marble shower restoration”! And that’s good news for homeowners, building owners, and for our natural resources of marble and other stone, too.


In the past, virtually the only solution available to homeowners or building owners with fine marble or stone showers was some level of demolition. For those lucky enough to have extra tile on hand, or to be able to find something similar, this went a little more easily, but the majority of installations required total or near-total demolition.


And that meant weeks of construction, destruction of valuable, one-of-a-kind stone, and all the related costs. Not fun!


Now, with the sound test, and TersoMR(R)’s unique solution for waterlogged showers, there’s a better, faster, less intrusive, and more sustainable option. To keep mold out of marble shower areas in your building, give us a call to learn more!



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