Greenboard Okay For Tub Surround?

[Briandl]

My understanding is that it's definitely not okay to use Greenboard for a tile backing. From what I've read it MIGHT be okay if everything is done just so and the grout sealed, but only a very small minority claim this, virtually everyone else says concrete type backerboard.

My understanding also is that USG says the following:

Panels are not intended for use in areas subject to constant moisture such as tub and shower enclosures

Does this mean it should not be used as a backer for a glue up tub/shower surround?

It's my understanding that greenboard was designed to be used in moisture areas like bathroom walls, but not specifically behind surrounds and/or tile.

If it makes a difference this is the greenboard from about fifteen years ago, not the newer type.

[jadnashua]

Current codes no longer allow greenboard in a tub surround or shower area. Not all areas use the latest codes. On a wet area, use cbu. While the covering is moisture resistant, the cut edges and screw holes pierce it, and the interior isn't much any better than regular drywall.

[SacCity]

To confirm -
Green board is not allowed by code behind tile.

That said when I was way younger I worked for a slum lord, and did lots of bathrooms with green board as a backing for tile.
Using green board we were getting about ten years maximum useful life out of a bathroom remodel. Most were less than that, but these were bathrooms that I did way way back when I was in High School and thats what my father wanted, but then again he was a slum lord.
Michael

[LLigetfa]

Does this mean it should not be used as a backer for a glue up tub/shower surround?

There is a big difference between tile and a one, two, or three piece surround. Schluter claims you can use KERDI over drywall in a shower. A tub surround would seal as well as KERDI.

That sais, I used DUROCK behind the KERDI in my shower. I've also installed a three piece tub surround over existing tile that was set on drywall.

[Basement_Lurker]

plastic/acrylic surrounds are non-porous, so drywall is fine so long as silicone seals are maintained. drywall around a drop-in tub is fine as the walls aren't going to be subjected to constant soaking. Drywall can be used in a shower space if an expensive sealing membrane is painted on and not trashed by a careless tiler. But if you intend on tiling, then a proper vapour barrier with either cbu/mud walls is the only way to go. Some people prefer to use the kerdi system, but IMO it's an overpriced and overhyped system targeted at the DIY crowd.

[Briandl]

What would you normally glue a glue up type wall surround to?

I'm starting to lean towards Kerdi on top of the greenboard, it's my understanding that there is an exemption in the IRC that allows for this type of usage, I'd then tile over that.

It was under the impression that just because something can create a physical barrier, that doesn't stop water vapor.

[jimbo]

It was under the impression that just because something can create a physical barrier, that doesn't stop water vapor.

I don't know about that statement. The mistake that has been made in the past was to assume that a grouted tile surface was waterPROOF....which it is not. Glazed ceramic tile is impermeable, but grout is porous..

[johnfrwhipple]

I use Green EBoard all the time in my tub surround and shower construction. Green EBoard is not Green Drywall but a tile backer board White in Colour...

[jadnashua]

Greenboard, for the discussion here, I think, is moisture resistant drywall...

This used to be suggested for use under tile in wet/damp areas, but is no longer approved for that purpose. Other products that may be green are not necessarily the same. In a shower area, unless it is covered by an approved waterproof membrane, you don't want to use drywall or greenboard. And, if you were going to use a waterproof membrane (or waterproof surround), then drywall would still work. Typical greenboard also isn't as stiff as drywall, so when used on a ceiling, generally calls for closer spacing of supports (i.e., 12" OC rather than 16" as used with typical drywall), or it can droop or bow.