: http://johnbridge.com/vbulletin/showthread.php?threadid=3698

: I highly recommend this site for tile advice. Search on the key words "moisture barrier". If you need help, post a question. Alot of pros will respond and give advice and encouragement.

: The whole issue of moisture barriers seems to be a can of worms. You will get conflicting information. You would think by now there would be a uniform approach but that doesn't seem to be the case.

: What I have been able to gather is this:

: 1) If using green board (do not use for showers of tub surrounds), do not use a moisture barrier. Kraft paper on insulation is okay.

: 2) If CBU (cement baker underlayment), use a moisture barrier of 4 mil poly or 15 lb tar paper.

: By the way I am a DYIer. So you will need to do further research.

:
: Well I'm about ready to give up on this DIY stuff. After insulating the exterior walls with fiberglass with Kraft paper, now I found articles saying whatever you do don't use kraft paper in a bathroom because it will produce mold. I had planned to install a 6 mill poly vapor on top of and 1 article says this is ok another says its not. Obviously I don't want to do something that could cause harm once installed. Anybody know the real answer, outside all the air movement and condensation lingo, is it ok or not is the q,,,I live in Michigan....Help....

The John Bridge forum is great but you are caught up in two different worlds. DO NOT have two moisture barriers or you will have the worst of both worlds. CBU/plastic barrier = best of both worlds.