Water – double vapor barrier

moistureshowertilevapor-barrierwaterproofing

I am constructing a mortar/cement board shower and i need to waterproof it. Is their anything wrong with using a plastic vapor barrier enter image description here / pvc shower pan liner enter image description here
for the bottom layer
and then also liquid membrane for the top layerenter image description here
are would this be a double vapor barrier and create problems?

Best Answer

It looks by what you're saying that it would creeate a double vapor barrier (or vapor pocket), however with the materials shown, it may not create "problems" per se.

That said, I don't know why you would do it using those materials. You could easily grout a tile a shower fairly cheaply and get a more rugged finished product. Personally that's what I would do because it is the standard, easy and correct thing for a shower...

Having said that, you could also just use your liquid sealant layer and heavily coat your motor board and get an equally water-proof later.

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