mold problem in marble shower

[Spanannie]

We have a large walk-in crema marfil marble shower in our new home. There is a step down into the shower and a bench at the other end. The shower does not have the best design, since there really needed to be more slope in some areas for water run down, but that is beside the point now.

There is a constant mold problem around the step down and shower bench. The mold is on the grout. We keep a brush in the shower and frequently work on the grout, but that doesn't get rid of it. We are using stonetech cleaner with the brush, but still have mold. Is there anything we can use besides the stonetech and a brush to get rid of the mold? I'd just love to get some bleach to that grout, but I would think that would be harmful to the marble. How do you deal with mold near marble? There's got to be something out there that's effective and safe for marble.

Thanks!
Annie

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[Steven Hauser]

Hi Annie,

First things first we have to get rid of the environment that is keeping the mold growing. :eek: I'm not talking about getting rid of the marble :shake:, but would like to know more about the slope in the shower and whether or not you know how the pan and bench were constructed.

1) Get into the habit of wiping the shower down after use. Dark, moist with little air flow is a great environment for mold. So let's remove the moisture.

2) Let's get the air moving to reduce the humidity in the shower. Is there a fan and light in there? If so leave it on for a while after use. Leave the shower door open after use. etc.

3) Cleaning. Although the Stonetech products are good for the stone :nod: they aren't formulated to stop mold. You will need a specific type of cleaning agent for that.
Our liberry has a formula for that. http://johnbridge.com/vbulletin/showthread.php?t=4991

4) There is something about the construction of the shower that is allowing the mold to stay there. A thorough inspection is necessary. The grout or caulking may need to be removed and the mod cleaned, the shower allowed to dry for a couple of weeks, and then reinstall all the grout and caulk.

Good luck.

:)

[doitright]

Hi Annie, Welcome! :)

Highlighting on the point of construction. If the shower doesn't have the proper prepitch under the liner, a lot of moisture can be acummulating in the pan. Short of redoing the pan (if necessary), the temp fix is to dry it out, recaulk, and seal the grout.

Does the bottom row of the marble on the walls at the pan appear to have any darkening (darker than the rest of the wall)? :shades:

[Spanannie]

Hi Steven,

My response in contained in your quote:

Hi Annie,

First things first we have to get rid of the environment that is keeping the mold growing. :eek: I'm not talking about getting rid of the marble :shake:, but would like to know more about the slope in the shower and whether or not you know how the pan and bench were constructed.

The pan and bench were fiberglassed in. The bench has no slope (and possibly sloped in the wrong direction) and the floor lacks shape for good drainage. We were so pressed for time in this phase of construction (had to get out of old house ASAP), that, unfortunately, I think we let some things go. Should we contact our builder about this improper construction/drainage? This home is still less than a year old.

1) Get into the habit of wiping the shower down after use. Dark, moist with little air flow is a great environment for mold. So let's remove the moisture.

We squeege after use.

2) Let's get the air moving to reduce the humidity in the shower. Is there a fan and light in there? If so leave it on for a while after use. Leave the shower door open after use. etc.

Always use fan and light; shower does not have a door.

3) Cleaning. Although the Stonetech products are good for the stone :nod: they aren't formulated to stop mold. You will need a specific type of cleaning agent for that.
Our liberry has a formula for that. http://johnbridge.com/vbulletin/showthread.php?t=4991

I assume that since you recommended this "recipe" that it's safe for marble? It's not too abrasive? I really don't know so much about taking care of marble, other than what I've read on the Net. All the supplier could tell me about was using their products, which I found outrageously priced.

4) There is something about the construction of the shower that is allowing the mold to stay there. A thorough inspection is necessary. The grout or caulking may need to be removed and the mod cleaned, the shower allowed to dry for a couple of weeks, and then reinstall all the grout and caulk.

We will look into this.

Good luck.

:)

Thanks,
Annie

[Steven Hauser]

:)

:nod: Contact the builder. This is an involved repair that will probably mean finding marble that might blend but not match. Stone is subject to change from block to block.

I want to change my answer now. :D

Don't do what I suggested, I would rather the builder fix the conditions that are causing moisture to accumulate.

Good luck, and I hope you have a secondary shower.

:cry:

[jerry in AZ]

I realize I am not a pro, and this reply is a little dated, but wont the formula for mold, http://johnbridge.com/vbulletin/showthread.php?t=4991 cause the marble to etch? Would hate to see someone read this later on and ruin there marble.

Jerry

[Steven Hauser]

Hi Jerry,

You are right of course, but only carboniferous material and dolomitic material (marble, travertine, limestone and onyx) will etch with the use of the vinegar and boric acid.

However, many stone types (granites, slates) and all ceramic and porcelains will not be adversely affected.
It also comes down to this, when a shower starts having mold issues, water is usually behind the material. This would require an extensive repair and restoration.

Another moderator brought this weakness to my attention this weekend. I told him I will get a formula that is suitable for all materials posted this week.

The problem of course it won't be as effective nor inexpensive.

Thank you for your keen eye.
:)