Remove or perforate original vapour barrier?

11 years ago

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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Comments (5)

Dando
11 years ago
If your vapor barrier is on the outside of the house (outside of the studs), Leave it.
alan_s_thefirst
Original Author
11 years ago
It's on the inside, warm side of the studs, as per usual.
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MongoCT
11 years ago
Leave the original vapor barrier intact and use a waterproof but not vapor proof barrier like Hydroban.
alan_s_thefirst
Original Author
11 years ago
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.
kirkhall
11 years ago
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)?