tiling tub surrond/vapor barrier


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Old 02-04-08, 02:33 PM
J
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tiling tub surrond/vapor barrier

Hello. I've been reading this forum for the past few weeks, and it has been invaluable as I work on our new bathroom. I'm at the point now where I'm ready to finish out the area around the tub, and I have a question I'm hoping someone can help me with.

We plan to tile the tub surround, and from all the posts I've read, I've become convinced that I should install a 6 mil. vapor barrier before I put up the cement backer board. I know the vapor barrier has to overlap the flange on the tub, but I can't figure out from my reading whether it should be caulked to the flange, or if it should just hang free. Any advice is appreciated. Thanks.
 
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Old 02-05-08, 03:50 AM
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You will want the vapor barrier to extend slightly below the cbu, and the tile will extend below both of them, so it won't be seen. You just want the layer effect to shed any water that should happen to get behind the wall. Hopefully it will be a redundancy.
 
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Old 02-05-08, 09:41 AM
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Thanks for the response, that helps a lot!

One other quick question: the wall on the long side of the tub is about a foot away from the cement block foundation in our basement (we had to frame the wall out that far to leave room for the gas and water meters). I previously insulated the cement block wall with XPS, and now I'm a little concerned that adding the poly sheet will create a "vapor barrier sandwich" situation. Should I be worried about this, or will the fact that there's a good 6 inches between the studs and the XPS be enough to mitigate moisture worries?
 
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Old 02-05-08, 04:02 PM
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No worry, the vapor barrier will keep the moisture from attacking your cbu and tile. What happens behind the vapor barrier will dry out on its own. There is air circulation back there to help.
 
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Old 02-06-08, 10:33 AM
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Good to hear, thanks again!
 
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Old 02-20-08, 12:06 PM
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Vapor barrier around tub.

I have kept up with this thread and I too am installing cement board around the bathtub, using the 6 mil clear poly behind it. I have a few questions before I actually install the board.

1) There is already loose yellow insulation and some paper face insulation in the walls, would using the 6 mil inbetween the board and the studs cause any harm to the existing insulation or paper?

2) For some of the wall, there will be drywall installed about two feet up down from the ceiling (densarmor paperless to be exact), will running the vapor barrier behind that too, cause any harm to either sides? studs, paper, yellow insulation, etc, ect?

3) Is it ok to staple the clear poly to the studs or should I go for some kind of adhesive? If I do staple do I do anything for the areas where the staples are in? (tape over it)
 
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Old 02-20-08, 01:19 PM
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1) There is already loose yellow insulation and some paper face insulation in the walls, would using the 6 mil inbetween the board and the studs cause any harm to the existing insulation or paper?
Slit the faced insulation with a utility knife.

2) For some of the wall, there will be drywall installed about two feet up down from the ceiling (densarmor paperless to be exact), will running the vapor barrier behind that too, cause any harm to either sides? studs, paper, yellow insulation, etc, ect?
Not familiar with densarmor but should not be any problems. see answer to 1 above

3) Is it ok to staple the clear poly to the studs or should I go for some kind of adhesive? If I do staple do I do anything for the areas where the staples are in? (tape over it)
Staples are good, no need to tape over staples. Youll make more holes when you attach the cement board anyway. Those holes wont hurt anything.
 
 

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