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details on attaching cbu for tub/shower surround

details on attaching cbu for tub/shower surround

Old 07-26-04, 10:27 AM
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details on attaching cbu for tub/shower surround

Hello all. I'm remodeling a bathroom with a friend. Significant water damage on the frame, so we ripped out the existing sheetrock and ply and will most likely replace the framing. Keeping the tub, but took off the plastic tub/shower surround and will tile this over. However, I'm not sure on a couple of things:

1) I assume the tub needs to be butted up directly against the framing members, correct?
2) I'm going to be using cbu (cement board) for the surround...my question here is does the cbu go OVER the tub flange and then the tile goes all the way down to the tub and is grouted/caulked?
3) Is it OK to attach the cbu directly to the wall studs (screwed, of course)?
4) as far as a vapor barrier is concerned, do I need one, and if so, would it go between the wall studs and the cbu, or on the other side of the wall studs between the studs and the drywall?

Thank you in advance!
Old 07-31-04, 04:28 PM
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2)Some say yes to the c.b.u. going down over the flange but i disagree wirth that as it causes more problems than the potential problem you are trying to avoid,meaning that when the c.b.u. goes over the flange it will flare out from the wall and then you have the bottom row at an angle and you have to angle in the tile at the corners as well as the durock on the adjoining wall.So set the rock on top the flange and then everything is straight,if water concerns you at the point where the c.b.u. meets the flange then silicone the joint.Make sure you fill in the crack with thinset to support the tile where the c.b.u. stops,or at least butter the tile eneough to support after the tile is put on.


4) My feelings on vapor barriers are that if you punch a bunch of holes in something that is supposed to keep moisture out then what good is it?Kind a like pi!!@#$ in the wind.If it was a steam shower then yes by all means but,it would go on top the c.b.u. and not under it.

Sorry it took so long for someone to answer this post
Old 07-31-04, 07:51 PM
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As floorman said - the cbu only goes to the top of the tub flange - not over it. The space left at the bottom behind it can be filled in with silicone prior to installing your new walls, which you didn't say what you are doing for a final finish.

One note, Durock does not need a vapor barrier as long as you tape the joints. Again floorman advised that once you apply a vapor barrier, making holes in it makes it worthless. There is a flip side to this however, CBU is not waterproof (it is pourous) and depending on the surround, any water that would get behind it will not destroy the cbu as it will sustain its rigidness whereas greeenboard would not.

The end purpose determines the application that should be used for cbu and/or vapor barrier.

Good luck!
Old 08-01-04, 06:29 AM
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Good point Doug i missed that, thank you

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