OK, so what’s the bottom line? Is “green board” still being made? Is it being used - and where is it being used - behind tile? on “wet walls”? Have manufacturers all gone to mold resistant gypsum board? There seem to be a lot of questions; what are the answers?
We had a similar discussion, now archived:
I think it was fairly comprehensive, but if you have other Q’s or comments or updates, post here and we’ll revisit it.
Well, that’s what got me to here in the first place. I keep hearing “mold resistant” and “no more greenboard”, but I don’t actually see that on manufacturer’s web sites or in their literature. I guess I want a statement “we no longer make moisture resistant gypsum board (greenboard); use mold resistant gypsum board instead” - something I can take to a contractor or change my master specification by! Is a definitive answer so difficult? Thanks, George - I needed that.
In some parts of the country municipalities are outlawing greenboard for backer board in wet areas, for example on Feb 1, 2006, Dade County, FL issued such an amendment to their Code of Ordinances. My phone conversations with reps from GP and USG has been that greenboard will eventually no longer be manufactured, until that happens we will probably still see its use in non-wet areas.
Per this link from USG, their brochure says not to use moisture resistant board in tub and shower surrounds (if you look at the same catalog in 2005, this language did not exist - I wonder if USG is seeing a lot of legal action regarding mis use of greenboard:
http://www.usg.com/navigate.do?resource=/USG_Marketing_Content/usg.com/web_files/products/prod_details/SHEETROCK_Brand_Water-Resistant_Firecode_C_Core_Gypsum_Panels.htm
Where have they been??
I haven’t specified “green board” in “wet” or shower/tub surrounds in over 10 years!
By the way - that goes for ceilings too!
Is “Mold-Resistant Gypsum Board” the correct term for the new material - I have a project where I may need to specify it - not in “wet” areas.
Theoretically you could use greenboard for a ceiling as long as the the shower is ventilated and not used as a steam shower, we on occassion still call for green board on the ceilings with furring spaced at 12" oc rather than 16". The problem with the Backer board products on a ceiling is that it requires a plaster finish, backer board is meant to receive tile not be used as a finished surface. If the shower is ever used for steam, we always specify cement board.
We have found that the series of boards put out by Georgia-Pacific [Dens-Armor, etc.] serve very well.
Just some building code clarifications:
IBC Section 2509.3 permits the use of water-resistant gypsum backing board (their term) on ceilings with framing at 12" o.c. for 1/2" and 16" o.c. for 5/8" panels.
Additionally, the 2006 edition of the IBC (Section 2509.2) restricts materials to cement, fiber-cement, and glass mat gypsum panels for tile backers in tub and shower walls and for walls and ceilings in showers. Water-resitant gypsum panels are only permitted for tile backers in water closet compartments. Regular gypsum may be used for tile backers in walls or other ceiling applications.
Yes, moisture resistant or “green board” is still being manufactured. Most of the mold and mildew resistant boards that are now available can be used in place of green board as a tile backer. Of course, neither green board nor mold and mildew resistant panels can be used in wet areas under the IRC and IBC codes. Hope this helps.
Here is a correction to the link Mr. Lazar posted:
http://tinyurl.com/3xxzey
The performance of a properly installed thin-set ceramic tile installation is dependent upon the durability and dimensional stability of the substrate to which it is bonded. Certain substrates materials used in wet areas are subject to deterioration from moisture penetration. According to the 2006 ANSI A108, AN-2.4.1 some backing materials are subject to deterioration when subjected to moisture. When a tile installation is subjected to frequent wetting, backing materials of concrete, Portland cement mortar, cementitious backer units (CBU), or masonry are recommended.
Tile Council of North America (TCNA) B413, B430 the two Details that incorporate Greenboard NOTE: Not to be used on bathtub walls incorporating a shower head.
ANSI 3.5.1.1 Caution Gypsum wallboard (ASTM C1396/C1396M) and water resistant gypsum backing board shall not be used on ceilings or critical exposure areas such as exteriors, showers, saunas, or steam rooms.
In my opinion if the backer board can not be used exterior, than it should not be used in a wet areas were you consistently (day in day out) apply more moisture to the assembly than the exterior assembly would ever receive, especial in the southwest.
Dale, I have to agree with you. I can’t remember the last time I specified MR gypsum board, but it would have to be more than 25 years ago.
Several years ago I reviewed drawings for a high rise condominium project in order to prepare specifications for the Contractor, yes my client was the GC, it seems the Architect did not believe it specifications…anyway, I found in my review of the drawings that the Architect was calling for MR Gyp Board as a backer board in bathtub and shower surrounds, when I pointed this out to the Architect…well, it was not pretty, I got my head handed to me…seems I being a small insignificant firm and the Architect being a large significant firm…well I lost that fight…the building was constructed with MR Board in those areas… to continue this story, same architect has now asked us to prepare specifications on another similiar project, after reviewing their current drawings, we found that MR Board is no longer specified in wet areas…probably due to code changes, I wonder if that firm even realizes the potential nightmares that may be forthcoming from all their previous work…live and learn.