Mold on tile in shower

Norrrrrrrrrrrrm said:

Hey Guys,
I have a situation where there is a bit of mold on a shower floor and a little bit on the wall. I suspect the sealer has thinned out and not great ventilation when the shower is used. The tile is travertine. What is the best way to go about cleaning this up without damaging the stone? I have read vinegar, but also read it is not good. Thanks, Norm

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Is the mold in the grout or on the tile?

angus242 said:

Is the mold in the grout or on the tile?

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A bit of both, mostly in the grout. The tile has some in the deeper crevasses due to the nature of the stone.

Another reason not to use natural stone in showers.

Your shower was not built with waterproofing in mind most likely. You may not have a pre-slope under the membrane. Do you know how it was built, step by step and with what materials?

Sealer has nothing to do with waterproofing a shower or keeping water out of the grout or tiles. I'm guessing your base and maybe part of your walls are saturated. You can bet it's much wetter behind and under the tiles than it appears.

You can kill surface mold with Concrobium, but I don't believe it'll remove the black, and you'll still have problem again.

Jaz

It was built with a 1/4'' slope per ft with the first bed, rubber membrane, matching slope again, then added another roll on waterproofing membrane for extra security and tiled. Do you think the second membrane is not letting the water drain even with the slope? Dal Tile had recommended the second membrane. I am a little concerned.

Norrrrrrrrrrrrm said:

It was built with a 1/4'' slope per ft with the first bed, rubber membrane, matching slope again, then added another roll on waterproofing membrane for extra security and tiled. Do you think the second membrane is not letting the water drain even with the slope? Dal Tile had recommended the second membrane. I am a little concerned.

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The application of a roll on membrane needs to be very specific and thorough. There is a certain thickness that needs to be achieve before it's considered waterproof. Even a pin hole or two can eventually make things go bad. Properly installed, moisture shouldn't be getting under it. Did the second roll on membrane cover the weep holes?

I wore socks when I tiled on top the membrane and I put two coats of the membrane down. The weep holes were not covered up. Dang.:sad:

Geez Norm, I dunno :001_huh:

I totally agree with Jaz. I'd bet there's moisture sitting under the tile or mud bed and that's the source of the mold.

Not that this helps you but for anyone else reading, this is why I prefer a fabric-style membrane (KERDI). I feel they are much more reliable in such a critical area.

I appreciate the help. After the posts I decided to get super stiff brush, turn the shower on and went to town on the tile as I showered. Nothing like multitasking. My main squeeze gave me a weird look when she looked in as to what I was doing. But most of the stuff came off then. I will go back and clean with another solution(concrobium) to see if it stops. I used a light acid before and it did not seem to do as good as a job as the brush and water. It has been 2 1/2 years since the shower was built and for it now to start was puzzling me. Like in my earlier post, I think my girlfriend and I are not letting the tile dry in time. I guess we need to shower together more often to prevent this problem! Thanks guys,
Norm

I used a light acid

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Don't use acid with stone.

Get some Zep Mold & Mildew remover, test it first on a small area to see if it does anything to the stone, if not, use it, no scrubbing, just spray it on, wait an hr. or so and rinse.

For any stone shower you better go to either mbstone.com or stonecarecental.com and buy both:

MB-3 and MB-9


I use them all the time and nothing is better or safer in an acid sensitive shower.

Norrrrrrrrrrrrm said:

It was built with a 1/4'' slope per ft with the first bed, rubber membrane, matching slope again, then added another roll on waterproofing membrane for extra security and tiled. Do you think the second membrane is not letting the water drain even with the slope? Dal Tile had recommended the second membrane. I am a little concerned.

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you are creating a moisture sandwhich with that recipe, the rubber membrane is the water proofing in a mud bed type base.

What kind of water is it? City punch or well?
I ran into a situation like that no too long ago on a well system. And the water needed to be treated. It was white gunky build-ups though, not mold.
How often is the shower cleaned?
Is there a vent fan in the shower area? And is it used?
It may be something as simple as a low spot where water accumulates and then the mold builds up.

For future reference, 1/4" slope is the MINIMUM. The slopes I do are almost double that amount.
I can tell you for sure, it is definitely NOT a sealer issue.

Run the water a few minutes. Shut off. See how long the water takes to disapear. Are there any "puddles" left anywhere?

There's a couple ads for VENT FANS on this page to the right and bottom.
You may want to buy one of them.
Nathan will appreciate it.

brzelt said:

For any stone shower you better go to either mbstone.com or stonecarecental.com and buy both:

MB-3 and MB-9


I use them all the time and nothing is better or safer in an acid sensitive shower.

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Never use an acid in a marble, limestone or travertine stone and vinegar is acidic. These products are what you need to help with the staining.

If the mold comes back, dilute bleach with water and keep in a spray bottle and spray the mold when you first see it return. Be sure it's diluted as the akaline bleach can cause some etching as well.

Where in my post did I mention using an acid product.


Read it again and try the products I said. They are magic on stone showers.

Actually, I agree with you and recommend the same products.

I was just stating never use acids when cleaning natural stone. When I posted, I noticed it look like I was contesting what you said, but in reality I was agreeing wholeheartily.

Sorry for the confusion.