Building a Shower question

[jjb4900]

ok, I'm getting ready to put up the cement board in my shower stall and am wondering if I should use a vapor barrier behind the cement board or use one of the paint on membranes that go on the outside of the board, something like Redgard......I've found so much conflicting answers it's really got me wondering which is better. I've read that a vapor barrier behind the cement board will trap moisture and not allow the walls to breath, which does make sense.....any thoughts?

[Lawdwaz]

 

Are you going to tile or use a shower surround?

Im going to roll the dice and say "don't use a vapor barrier". Just use your cement board or DensShield type material.

 

[jjb4900]

tile....I'm reading that vapor barrier doesn't let it breath and that a paint on membrane screws with the tile adhesion, so I don't know.

[virgil]

I'm not familiar with paint-on membranes.  But, I've always used a vapor barrier behind the cement board.  You can use tar paper.

[jjb4900]

19 minutes ago, virgil said:

I'm not familiar with paint-on membranes.  But, I've always used a vapor barrier behind the cement board.  You can use tar paper.

thought about that as well and only going up half the wall to give it some breathing room.

[nycredneck]

If it's an outside wall, first is insulation then I put a plastic sheet vapor barrier, then the cement board. Ive had no problems in the last 15 years.

[Culvercreek hunt club]

1 hour ago, nycredneck said:

If it's an outside wall, first is insulation then I put a plastic sheet vapor barrier, then the cement board. Ive had no problems in the last 15 years.

This is the correct approach. 

[jjb4900]

1 hour ago, Culvercreek hunt club said:

This is the correct approach. 

so you're saying I should take em down and install the barrier? only have two sheets up so far, and what about uninsulated interior walls?

[Culvercreek hunt club]

should have the vapor barrier behind the cement board. I carry from the ceiling out onto the base. Install the cement board and trim. if there is ever any moisture that gets through the tile it goes down and to the base. The biggest issue I see with tiled or stone shower walls. The owners almost NEVER keep up on sealing the grout and stone. Stay up on that and you won't have an issue. 

[jjb4900]

yeah, I'm going to keep it as is and just do bottom half of the wall, the manufacturers of the wonderboard call for no barrier......have you ever used the paint on membrane?

[Culvercreek hunt club]

Never used the coating.  With things like this you want a complete system. By the letter for what the mastic/adhesive calls for. 

[jjb4900]

yeah, the coatings get great reviews but I'm concerned about making the surface too smooth with not much for the tile to adhere to.....