How many walls do I vapor barrier in tub alcove?

Users who are viewing this thread

ironspider

Member
Messages
70
Reaction score
0
Points
6
Location
Michigan
Greetings all,

Got my tub shimmed and in place now in the tub alcove. I got some 6 mil vapor barrier and I am ready to put that up before I get on to the cement boarding and tiling and such.

My question is though, do I vapor barrier all three walls of the surround (it's a right drain alcove so I have the left wall [exterior wall], back wall, and then the right wall [where the plumbing is]) or just the back and left walls?

Oh, quick addon question, do I need to use cbu on the back side of the wall with the plumbing? or just the side that faces the tub? I'll throw in a quick terrible diagram explaining (I mean do i need to use CBU on the red line in the diagram below or just in the gold areas?):

cbu.jpg



Thanks!
 

Jadnashua

Retired Defense Industry Engineer xxx
Messages
32,771
Reaction score
1,191
Points
113
Location
New England
Use CBU on all sides. Where there may be insulation already, so you don't end up with a vapor barrier sandwich, cut the existing vapor barrier (random slices are okay) then install a new, intact one on all three walls. Lap the vapor barrier over the tiling flange, ideally, either notch the studs or shim them so the cbu doesn't get bowed out and run that down over the lip. If you are using a larger tile, you can stop the cbu above the flange slightly. Cut the vapor barrier prior to tiling, ensuring it is still overlapping the tiling flange. The cbu should go up at least to the level of the showerhead, but can run higher if you want.

For good tiling help, check out www.johnbridge.com. Lots of pros there that can answer tiling questions.
 

Frenchie

Jack of all trades
Messages
1,239
Reaction score
0
Points
36
Location
Brooklyn, NY and Fire Island, NY
Greetings all,

Got my tub shimmed and in place now in the tub alcove. I got some 6 mil vapor barrier and I am ready to put that up before I get on to the cement boarding and tiling and such.

My question is though, do I vapor barrier all three walls of the surround (it's a right drain alcove so I have the left wall [exterior wall], back wall, and then the right wall [where the plumbing is]) or just the back and left walls?

All three walls, but just the side facing the tub.

BTW, make sure you get a decent seal around the plumbing fixtures, that's where most leak damage occurs.

Oh, quick addon question, do I need to use cbu on the back side of the wall with the plumbing? or just the side that faces the tub? I'll throw in a quick terrible diagram explaining (I mean do i need to use CBU on the red line in the diagram below or just in the gold areas?):

cbu.jpg



Thanks!

Your description was a bit confusing - did you add this question later? Because reading Jadnashua's response, I get the impression you hadn't posted the picture yet, when he answered.

Anyways - looking at the drawing: yes to all the yellow, no to the red. The red side of that wall gets no vapor barrier, and does not need to be CBU, it can be drywall.
 

Jadnashua

Retired Defense Industry Engineer xxx
Messages
32,771
Reaction score
1,191
Points
113
Location
New England
I beg to differ...compromise the existing vapor barrier on the outside wall above the tub, and run a new one over it (you don't want two layers!), and run that one down over the tub lip just like on the other sides.

Drywall on ANY side of a tub/shower is a lousy solution and DOES NOT meet national codes or the TCNA guidelines. Yes, that wall doesn't get anywhere near as much spray as the others, but is does get wet. The paper on drywall only needs to get wet a little and mold can start. Why risk it? CBU will not degrade even if you soak it in a tub of water...drywall gets really nasty.
 
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks