I'm tiling a shower. I put 6mil vapor barrier behind the cement board but weant to be sure the application is entirely waterproof. I'd like to cover the cement board with RedGard prior to tiling. I've read a few posts on the internet saying this is a bad idea because it will "trap" water in the cement board! I realize that the Red Gard may be overkill, but would it be problem to use it over cement bpard that has a vapor barrier behind it?
