Hi, I'm framing in a new stall shower, have looked at web sites on the subject and most experts suggest putting a moisture barrier under the cement board. I can see why that would be good. One company, which produces a thick (15 mil) membrane for this application, also shows a detail in which a silicone sealant is used between the membrane and the backer board. There is no mention of brand of sealant, and it doesn't seem they sell it. This is a first for me, and I'd like to learn (from an impartial third party) if this is standard practice.

Thank you

Tony Tammer

Hi, I'm framing in a new stall shower, have looked at web sites on the subject and most experts suggest putting a moisture barrier under the cement board. I can see why that would be good. One company, which produces a thick (15 mil) membrane for this application, also shows a detail in which a silicone sealant is used between the membrane and the backer board. There is no mention of brand of sealant, and it doesn't seem they sell it. This is a first for me, and I'd like to learn (from an impartial third party) if this is standard practice.

Thank you

Tony Tammer

Hi Tony,
I waited for another expert to jump in as I just pipe in drainage and water and don't build the shower floor or enclosure.
Here's a link that may take some of the mystery out of it. Click on;
http://www.compotite.com/skyblue.html
To see diagrams and instructions. Good luck, Tom

Yes a moisture barrier is recommended and if you are putting in a shower pan I believe you should run the barrier inside the shower pan liner.

Check johnbridge.com and the forums there. They have some people that really know shower stalls over there.

Tom

Just to make sure... you said under?? Are you putting the backer board on the floor of the shower?