Remove or perforate original vapour barrier?

alan_s_thefirstAugust 9, 2012

Ok, one more question: If I'm going for an applied waterproofing agent - Kerdi, or a paint-on over backerboard, do I remove or perforate the original vapour barrier? One section of the shower - only around 2-3' x 1' - is on an outside wall. Should I do this, or should it remain as part of the building envelope? It would effectively sandwich the backerboard between waterproof membranes.

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Dando

If your vapor barrier is on the outside of the house (outside of the studs), Leave it.

    Bookmark   August 9, 2012 at 5:14PM
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alan_s_thefirst

It's on the inside, warm side of the studs, as per usual.

    Bookmark   August 9, 2012 at 6:01PM
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mongoct

Leave the original vapor barrier intact and use a waterproof but not vapor proof barrier like Hydroban.

    Bookmark   August 9, 2012 at 10:10PM
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alan_s_thefirst

It doesn't look like I can get Hydroban where I am and I don't have time to buy and ship...I was planning to use Redgard, but it looks like it's 100% waterproof, so I'd be back to the question of two barriers, so I guess the original one goes. Not sure what to do for a transition, but it's a small area above the shower, about 1' high, 2' long.

    Bookmark   August 10, 2012 at 9:10PM
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kirkhall

Mongoct! Question that feeds off this question.

If one chooses to use hydroban (and it is not a vapor barrier) does one need to use a vapor barrier also (such as plastic sheeting behind the cement board)?

    Bookmark   August 11, 2012 at 10:06PM
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