Green Board or Black Board or... [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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01-08-2003, 12:46 PM
Having a bathroom retiled, the contractor will be removing the wall board around the tub area. Some of the arm chair home improvement experts I work with are telling me that I have to have blackboard put up, not greenboard as the tiles will adhere to it better and there will be better moisture protection. True or false or it doesn't matter??????:confused:

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01-08-2003, 12:55 PM
The correct answer is Cementeous Backer Units (CBU).

Green board is sheet rock with a slightly better water resistance. But not good enough. If you let them use greenboard for your shower or tub surround, you will get to rebuild it in a few short years!

A moisture barrier goes up before CBU.

John Bridge
01-08-2003, 06:25 PM
Hi Shawnee,

I'm going to have to guess at what "blackboard" is. It's obviously a regional vernacular. :) I think is is outdoor sheetrock, whose paper covering is very dark gray.

In any case, forget it. Bob is correct. Cement backer board is the way to to (unless you can find a mud man lounging around somewhere). :D

01-08-2003, 06:44 PM
I think it may be even worse than that, John. The only thing we refer to as "blackboard" is a pressed fiber and tar sort of compound. Looks kinda like fluffy half-inch roofing felt but it ain't even as water resistant. Frequently used as exterior sheathing behind rock veneer. Not even worth consideration for a shower wall.

Could your "quarterbacks" have said "backerboard", rather than "blackboard"? That would mean they were your friends. Otherwise, I would refer to them as acquaintances. :)

See can you get a more scientific name for us.

John Bridge
01-08-2003, 07:49 PM
Oh, geez, yeah, "Homosote," the impregnated kind? Used as an exterior sheathing sort of. Around here they call it black (close your ears, ladies) -- they call it "black shit." ;)

01-08-2003, 10:38 PM
Oh God John...I've come across that "stuff" too cept they call it Beaver board 'round here...I like your name better...:D

I think they were talking about the Exterior Gypsum sheathing as John first indicated...but that stuff has the paper imprenated with WAX ! How you gonna get anything to stick to that ?

but I really hope they meant backer-board that's the next best thing to mud.....

01-08-2003, 10:48 PM
Beaver Board hereabouts is OSB, rj, and that ain't black. :)

Let's all hope for CBU.:nod:

01-09-2003, 07:42 AM
:bang: Yep, they "meant" backer board, although others in the office insist they said blackboard. Glad that is settled, and thanks for all the help. :wave: (liked this one) As usual yuzz gyz came through.

01-09-2003, 08:52 AM
There is a sheetrock product that is commonly called blackboard hereabouts. In these parts it's commonly used in tract homes in bathrooms and such. It's a bit better than greenboard as far as holding up to moisture supposedly. I've actually installed a bunch of it for GC's , once, in a GC's house even, in his jacuzzi room. Total crap, basically it's sheetrock with a overdose of fiberglass mixed with the gypsum and pressed between black paper. My biggest complaint with it as a sheetrocker is that it eats knife blades and rotozip bits for breakfast and kicks out a mountain of dust when you use a rotozip for cutouts, which is why I always charge a bit extra to hang the stuff. I have seen tile set directly on to it and in fact until I found this fine site I thought it was an acceptable practice.

But then again since I started frequenting this site I've learned a whole lot that I never knew that I didn't know. And have gotten a few raised eyebrows from GC's when I pointed out some of this new found knowledge. :shades: