Green Board over Vapor Barrier?

Pineapple · 11-17-2008, 12:58 PM

I'm working on remodeling my bathroom. I'm at the point where I'm starting to hang drywall back on the walls! I've already purchased a bunch of "green board" for the walls, since this is a bathroom. However, I've read that it is not a good idea to use green board over any sort of a vapor barrier. Is this true? The room originally had (and still has) foil-faced insulation around the shower with a poly vapor barrier stapled across the studs. Should I remove the poly before installing the green board? Or is it safe just to go over it?. I think the concern was that moisture could accumulate on the surface of the poly, thus dampening the green board. Just curious to hear some thoughts.

Thanks,

bradnailer · 11-17-2008, 02:24 PM

I'd use cement backer board for the shower area not green board but then that's just my opinion. Green board is water resistant but not water proof.

Pineapple · 11-17-2008, 02:44 PM

I'm already somewhat committed to the green board in that I've bought a whole bunch of the stuff! Don't really wanna go through the hassle of borrowing a truck to buy anything different. Right now I'm just debating whether or not I should rip off the poly vapor barrier.

bradnailer · 11-17-2008, 03:43 PM

Sorry to be persistant here, but you are just asking for problems using greenboard in a tub/shower enclosure. Borrow a truck and swap some of the greenboard for hardibacker.

Pineapple · 11-17-2008, 03:51 PM

Well, I'm not really installing greenboard IN the show enclosure. I've already installed a new fiberglass shower enclosure directly over the stud walls. I now have only to cover a 2' section of wall between the top of the enclosure and the ceiling. Regular drywall hung on these walls for the past 30 years, with the poly vapor barrier behind - no issues. My concern now is, with greenboard, should I remove the poly vapor barrier behind this 2' section surrounding the top perimeter of the enclosure.

bradnailer · 11-17-2008, 05:01 PM

Sorry, didn't clearly understand your situation. According to everything I've read, no vapor barrier should be used behind greenboard.

Pineapple · 11-17-2008, 06:26 PM

Yeah, that's what I've been reading too. Alright, poly vapor barrier is gone! Now what to do about the foil-faced insulation? I could rip of the foil. But this is an exterior wall, so don't I kind of need some sort of vapor barrier? I'm thinking the foil won't be as bad as the poly when it comes to condensation. Could be wrong though.

bjbatlanta · 11-18-2008, 10:21 AM

If you're just worried about that particular area, buy a sheet of Densarmor to hang the top of the tub. It will require a "glaze coat" of joint compound to get it smooth to blend in with the rest of the rock, but being "paperless", mold won't grow on it (according to mfgr's claims). I doubt enough moisture would ever accumulate to actually deteriorate the Densarmor (as attested by the regular board that survived 30 yrs.).