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02-29-2008, 06:16 AM
I hope I haven't screwwd up. I put down my poly vapor barrier then my hardi-board. Since then I have got "moisture paranoid". I coated the walls with red guard and am ready to tile. Is this going to be a problem? I have read now that this might create a moisture problem!!??? Is this right. Thanks

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02-29-2008, 07:08 AM
I'm new to all of this myself.
If the Red Gard holds up, then there shouldn't be a problem with a "moisture sandwich". I'd suggest making sure that you coat the hell out of the backer board.
But let some others answer before doing anything

Dave Taylor
02-29-2008, 10:11 AM
I sure don't understand how you could read and review this site.... yet miss all the posts and threads that advise against doing.... exactly what you did; create the possibility for moisture containment and mold growth by building a "moisture sandwich".... which is exactly what you accomplished by sealing CBU between two moisture barriers.... polly on one side of the CBU and RedGard on the other.

Moisture will enter this area.... either by wicking or condensation if not by more direct means and.... it's exit will be restricted by the double barrier you have installed.

I wish I could agree with “MikeyL”…. that all is hunky-dory…. that you will never have a problem with this double moisture barrier…. but I can’t.

Any way you can put slits in that that polly sheeting on the back of your CBU?

02-29-2008, 10:25 AM
Hi Dave,
Unfortunately I had already built the enclosure and float and taped it, etc. It is then I had the brainwave of putting on the extra protection. I can't really rip it out now(bench built,nich,etc.) Will it be a serious problem? How much moisture are we talking? If the redguard does it's job, shouldn't the problem be very minimal?
Thanks, ken

02-29-2008, 11:15 AM
Hello Ken, Sure, the problem COULD be minimal, but it could also be huge. Wanna roll the dice? Probably not a good idea.

Can you peel the Redgard off the Hardi?

02-29-2008, 11:28 AM
The "moisture sandwich" problem is theoretical . And while I respect all the opinions on this board, i think the problem is overstated. The ease by which moisture will readily flow through 3 coats of Redguard will be matched by the same ease of that same moisture evaporating through that same Redguard.

Personally, I don't think more than a drop of moisture will see the inside of your CBU. Your point about Redguard doing its job is well taken.

Leave it in place. Sleep well.

02-29-2008, 11:28 AM
I just put one light coat on it , other than the nich and bench. I don't know if it is that waterproof that light anyway. I may be able to peel some off, I don't know.

02-29-2008, 11:30 AM

You make me feel better. I may continue then with the additional coats.


Dave Taylor
02-29-2008, 11:59 AM
which discuss the "moisture sandwich".


Your house. Your shower. You decide.

02-29-2008, 12:26 PM
I hate to make matters worse, but I had this same concern before I put up my Kerdi. Different opinions about the poly vapor barrier on the outside wall, then CBU, then kerdi. So at the time I called Schluter to speak to a rep and they said it was not a problem, and the vapor barrier under the CBU should not be taken down, which of course would have ruined my moisture barrier for the outside wall.

Like Dave said earlier, your house, you shower, your money. Never going to get everyone to agree on this.

02-29-2008, 01:18 PM
Just like Fox News:

"We Report. You Decide."

02-29-2008, 04:39 PM
Have you checked with Custom Building to see what their thoughts are?
Custom Building's homeowner warranty page (http://www.custombuildingproducts.com/ResourceLibrary/HomeownerWarranties.aspx?user=pro&lang=en)
There's a "contact us" tab on that page if you want to shoot em' a note to get their suggestion for installation. For that matter, they may have it listed somewhere there also.
It may give you piece of mind. Then again, it may not?