# Possible mold under shower tiles



## RachelW (Dec 30, 2008)

I recently pulled up some of the floor tiles in my shower because they had come loose. When I did, one spot had a strong, earthy kind of rotting wood smell like you get when you turn over a rotting log in the woods. 

I can't see the mold, all I see is the remains of the adhesive and the sand layer under that.

What would seem to make sense is if I can't see the mold then I need to dig through the sand layer until I do and THEN take care of whatever damage is there.

My husband is trying to argue with me, he thinks just pouring a boat load of bleach on the open areas will solve the problem.

I'm going to have to readhesive the tile. If I'm stuck doing that anyway, I want to do this right and not have to run into this a month from now.

So, what do I do?


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## Termite (Apr 13, 2008)

It sounds like the tiles were improperly installed in the first place. Was adhesive used, or is it concrete-looking thinset mortar? If adhesive, re-sticking the tiles is a short-term repair.

Personally, I'd opt for bleach and scrubbing as well, but if there is a water problem nothing but a correct installation will fix it.


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## RachelW (Dec 30, 2008)

*Oye*

Let's just say, I would not be surprised at the former owners if they had done it wrong.

I can't tell what kind of adhesive was used, it's so thin I can't even chip it off without going into the sand. I'm amazed it held on this long.

From what I've seen on DIY shows, the adhesive is supposed to be thick enough that the whole tile kind of nestles in it, this looks like it was just touching the thick parts of the tile but not the grooves.


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## ccarlisle (Jul 2, 2008)

Don't know if this is any consolation but you're not alone...I'd venture to say that 50% of the showers built in the last 25 years have or have had the same problem as you. It is indeed an "improper" shower construction -maybe even an "improper" tiling job.

And I'm viewing this with 20:20 hindsight, I know. Because what we know now is much more than was known a few years ago, as shower construction has come a long way since 1990 or so. Nowadays it is not uncommon to offer extended warranties on showers that range in the 30+ years, as opposed to the 'typical' shower construction that some offer , which is measured in <5 years. It is not a cost issue - it's just knowing the basics and delivering value to buyers.

The water is not running away completely, so the shower stays humid; wet everywhere, including inside the cement your shower floor seems to be made from. So, mildew grows and smells.

Now you can correct the problem and have a shower that 'dries out' - or you can kill off the existing mildew with a bleach. Now whether it;s sodium hypochlorite ('laundry bleach') or a peroxide-type, the bleaching action is temporary at best. Once the bleach has been used up, back comes the mold and mildew.

If you just moved into your house and plan on staying there for 5+ years, perhaps sell it when the market gets better, many here would advise a replacement of the shower. Right back to the studs. 

Oh yeah, and find yourself a shower guy who knows about waterproofing. In the end you'll be glad you did.:yes:


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## wrangler (Oct 9, 2008)

It sound as though the entire floor has failed. You say that there is sand, but I am thinking that that was once the mortar bed which IS now just basically sand, and useless to try and put the tiles back in. During a recent shower conversion, I had what sounds similar to your problem... what appeared to be a few loose tiles. When I DUG further, I found the entire base was full of moldy, wet mortar and had to be removed down to the slab. Here is a pic (sorry for the poor quality from the camera phone)


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## onlinehandyman (Aug 21, 2008)

*check further*

What does the area under the tile look like? Sounds like you probably have a bigger problem than just a few loose tiles, but I sure would like to get a look at the area under the tiles that came off. Everything may be stable and your problem might just be in the adhesive level, but see if you can remove any more of the surrounding tiles. My guess is I'll bet that you can. Then you will have a better chance to see what is going on below. Good Luck!


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## RachelW (Dec 30, 2008)

*Update*

Well, I have more info.

The "sand" stuff under the tiles is thick-set mortar. That would explain why I've had to take a chisel to it.

I dug a big chunk out and went down to the plastic liner underneath.

The good news is the mold was in the thick-set itself and it's white mold, not black.:wallbash:

I am NOT in anyway surprised the tiles were messed up to begin with, I'm debating about just ripping up the rest of the floor tiles and resetting the whole flippin mess.

What it looks like is a crack formed in the area of the mold. Where the crack originated I don't know, but it was pretty obvious in the thick-set.


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## ccarlisle (Jul 2, 2008)

You have a standard 'mud-bed' shower, made in a traditional way, using a sloped bed of "mud" (what you call 'thick-set'), sitting on top of a plastic liner which, in turn, sits atop another sloped bed of mud, all three layers tied into the drain assembly. Only the top layer gets wet. I know a lot of shower guys do this but it takes know-how to do a good job of it...one mistake, one scratch and you have what you've got a look at a complete re-do. The slope works out to about 2-3" at the edges to about 0.5" at the drain. The tiles are then set on this mud using thinset, not mastic.

This "system" never really dries out from one shower to the next, and in fact can take a week to completely dry out without even using it...the concrete mud is porous and therefore stays wet, thereby allowing mold to form. The mud can crack; if its the uppermost layer, then the water goes through the grout, through the upper layer of mud, hits the liner and runs off to the drain. No problem, really. But it shouldn't crack. Anywhere...Cracks show something's wrong and are a good site for mold accumulation.

You _can_ patch it, killing off the mold etc and make a reasonable job of it if you do; I wouldn't. Because I wouldn't want to redo it in 6 months and I'll forever know I didn't do it properly. Professionally, had I been your contractor, I'd point out that it's cheaper in the long run to replace the floor, but if you insist on patching it, I have a competitors phone number for you, and let him take the shot at _his_ repututaion - that type of job I can't afford. 

I can't tell you what to do; but your shower shouldn't do what it's doing, and that tells me there's a problem. As someone who does showers, I can tell you that the best option is to replace it. Removal of the existing, setting a Schluter tray and drain kit ($500), waterproofing up the walls abit, setting the new tiles the same day, grouting the next. Two days tops.

:thumbup:


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## Bud Cline (Mar 12, 2006)

Rachel that subfloor is trashed. It's all over for that one. You can not repair what is there. You may be able to gently remove the tile and the cement and save the liner. Cast a new cement base over the existing liner and re-tile but trying to save that mess is going to be throwing good money after bad.

White mold is generally associated with vegetation. I think what you are seeing could be an accumulation of hard water minerals and maybe some efflorescence, not necessarily mold. Shower mold would be black in this case.

At any rate...that shower receptor is shot and needs to be replaced.


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