New answers tagged vapor-barrier
plastic behind cement board with waterproofing is essentially suspenders when you already have a belt. the waterproofing is also a vapor retarder so if the red guard or kerdi product is continuous, lapping corners and all, the plastic will be unnecessary. if you think of tile like exterior cladding, it would make sense to leave an open hole in the ...
Lowes recommends installing a plastic vapor barrier behind the backer board in addition to a paint-on barrier between backer and tile. Source.
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