# Bathroom Remodel and Mold Issue



## jjump (Feb 12, 2010)

Hello all, I have a question that I was hoping to maybe find some solutions for. I've talke with several people at Home Depot, Lowes and another local builders supply (Busy Beaver for those in the PGH area)....

Anyways, here is my issue.

I live in a mid-80's Maronda home and I have the typical quality and building issues that these homes come with, and I have been fixing and remodeling over the years.

My latest issues has to do with the bathroom. My 60" long shower wall faces the outdoor wall, and I have 2x4 construction with T1-11 siding, R-13 was in the stud cavities.

Well, today I pulled the old tub and shower out and behind the insulation the inside of the T-11 was cold, some ice was on the inside, and mold was all over the inside of the t1-11. It seems the inside is getting wet. I dont think there is leaking, it seems to be from condensation, and I assume during a good hot shower, the vapor is getting through.

So I scrubbed the t1-11 with some bleach and i got it pretty clean, but it is still damp, and I worry that it will be damp until spring, but I need to get this tub back together.

My plan was to get it as clean as possible, install new insulation, and come spring, I would pull the T1-11 and put new pieces in from the outside.

I was also considering installing cement board to the back wall over the studs, then installing the new tub surround. Even though the new unit is direct to stud mounting, I dont see an issue with adding a 1/2" of cement board.

I worry though that this is just a band aid, and eventually the issue will come back, but I will never know.

SO, any advice here? To recap, I have mold on the inside of my T1-11 in my bathroom, behind my shower, I believe its from condensation. I have been cleaning it, and tomorrow i plan to get it as clean as possible and install new insulation and a new tub. I may add 1/2 cement board between the new tub/shower and the outside wall.

Thanks for the advice.

Justin in Pittsburgh


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## Kevin M. (Nov 26, 2009)

jjump said:


> Hello all, I have a question that I was hoping to maybe find some solutions for. I've talke with several people at Home Depot, Lowes and another local builders supply (Busy Beaver for those in the PGH area)....
> 
> Anyways, here is my issue.
> 
> ...


Justin,

Do you have a bath fan which is in working order and sized correctly for the sq. ft of the room? Removing the culprit (moist air) will solve the bulk of your condensate problems. 

You may want to use Denshield if you add to the wall instead of cement board. It has a vapor shield built into it. It is quite a bit easier to cut and install. 

Good luck,

KM

BTW..... If you add a 1/2 inch to that wall it may affect your plumbing a bit as far as tub drain etc.......


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## Big Bob (Jul 27, 2007)

Do you have a vapor barrier ( felt or tyvek ) behind the T1-11?

you mentioned you were able to scrub the "mold?" off the back side of the T1-11 once tub, surround and R-13 was removed.


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## jjump (Feb 12, 2010)

I believe my fan is sufficient, the room is only 60 sq. ft. It is 5' wide by 12' long.

As for the Denshield, the guy at Lowes told me that it might not be a good idea to use this, for my insulation (new that I added) had a vapor barrier, and the Denshield would have one, and you could get vapor caught between the 2 barriers.

Yes, I had to move all of the plumbing over 1/2", this was fairly easy to do though.

I sprayed the modl with bleach for 2 days, and scrubbed it with clorox, and let it dry for almost 2 days. It was till a bit damp, but I got it as dry as possible so that I could put in new insulation and get the new tub installed.

My plan is come Spring, I will remove the T1-11 from the outside and put new sheets on, but I cleaned it pretty good, I am hoping that I may not have to do that.

Ive attached a picture for review. It shows the mold along the outside wall behind the surround, towards the top of the picture was an area that I had already cleaned, you can see the difference.

My belief is that the old tub and surround were never "sealed" and vapor was getting in behind the insulation, since the insulation was installed poorly, the vapor would hit the back wall and condense.


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## Big Bob (Jul 27, 2007)

My belief is that this is water intrusion from the outside.

Test it with a hose.


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## Rory Read (Feb 9, 2010)

*tub surround substrate*


You hear "T1-11" and it's hard not to suspect the failure could be on the exterior.
 If I used cement backer board or densshield, I would go over my substrate with something like redgard. I don't think this is the way to go though, but maybe I am missing something.
 If I really felt a need to add a layer between the surround and the wall, I would use some thick polyethylene sheeting (thick only because I am less likely to tear it while I am installing the surround).
 I personally think that a fiberglass surround would be a pretty tight vapor barrier. I would just pay very close attention to the seams and fasteners, using plenty of high quality silicone caulk. If vapor/water is going to get past the fiberglass, it's going to be where the wall meets the tub or possibly the penetrations. This what they make boats out of right? It's the same material as the tub.
 Ideally, you would have used an unfaced batt instead of a faced batt, but the paper face is not super tight, and modest amounts of vapor will still move through and around it. I would not pull it if it was already installed.


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