07:01PM | 11/30/06
Member Since: 04/25/05
1915 lifetime posts
"I honestly don't believe that 99% of the staff at both local building stores I went to would recommend the wrong product, "

If you are talking about places like HD and Lowes they are famous for many of the employees not knowing what they are talking about.

"My point is that cement board too will fail under moisture eventually,"

No, you can soak an of the CBU's in water forever and it won't fail.

It is completely water resistant. But it is not waterproof. That is it will allow moisture through.

That is why you want to install a barrier behind it to product studs and insulation behind it.

There are also different trowel on, paint on, and films that can be applied over the backerboards (of any kind) to water proof the assembly.


02:53AM | 12/01/06
Member Since: 11/06/02
1280 lifetime posts

The link here contains photos showing exactly what I have seen four times where tile was applied over greenboard in a shower application. I was the one called to rebuild things. I have also seen the same with plain drywall.

I am a professional remodelor with 35 years of experience. There was a time when I installed tile over greenboard, but I learned better - a long time ago. I am trying to help others profit from my experience. If you want to continue to insist that greenboard is acceptable, be my guest, but that does not make it so.

Another point to clarify is you advice above that the joints should be taped and caoted with "mud" before tiling. Ordinary premixed drywall joint compound will disolve on its first exposure to water. It is important to use a mixed setting type compound such as Durabond which sets through a chemical reaction with the water in the mix rather than by dying in order to have a permanent water resistant "mud"

I am not pointing all this out so much to argue with you as to make sure others reading here have the correct information when they attempt to DIY their bathrooms.

'nuff said

Excellence is its own reward!


07:55AM | 12/01/06
Member Since: 01/28/03
693 lifetime posts
Actually greenboard CAN still be used in tub and shower compartments as a tile backer.

'Best Practice' notwithstanding, wherever the 2003 International Residential Code is in force, it is 100% permissable and Code compliant to use moisture resistant gypsum board as a backer for tile PROVIDED no vapor retarder is used under the backer and all edges are sealed according to the manufacturer, and the material complies with either ASTM C1178 or ASTM 630.

Section R702.4.2 (2003 IRC) GYPSUM BACKER: "Water-resistant gypsum board shall not be installed over a vapor barrier in a tub or shower compartment. All cut or exposed edges, including those at wall intersections, shall be sealed as recommended by the manufacturer."

The reason no vapor barrier can be used behind greenboard is because while greenboard is only "moisture-resistant" and not "waterproof", as already mentioned, and although it CAN withstand occaisional wetting and even saturation...Moisture resistant drywall cannot withstand CHRONIC wetting and can breakdown under such conditions.

Using a vapor retarder such as black paper, or plastic sheathing or other material under greenboard in a shoer compartment can create a "Double Vapor Barrier" which can chronically trap moisture within the drywall sheet. This will contribute to its failure because once internally wetted, moisture cannot escape from within the board because of the double vapor barrier on either side and be allowed to dry.

Eliminating a vapor retarder from behind greenboard can eliminate or reduce damage from leaked or condensed water.

Now, that is NOT to say that one SHOULD use greenboard.

I wouldn't do it and do not recommend the practice.

Concrete backer products are indeed superior for the application.

But it remains completely permissible and Code compliant to use "greenboard" whenever and whereever the 2003 version of the IRC is still or will continue being used.

That said, the 2006 International Residential Code has DISALLOWED the use of tradtional 'greenboard' but still allows other types of gypsum products as tile backers in showers:

R702.4.2 (2006 IRC) CEMENT,FIBER-CEMENT, AND GLASS MAT GYPSUM BACKERS. "Cement, fiber-cement or glass-mat GYPSUM backers in compliance with

ASTM C 1288, C 1325, or C 1178 and installed in accordance with manufacturer's recommendations shall be used as backers for wall tile in tub and shower areas and wall panels in shower areas."

So gypsum products are STILL allowed by Code as tile backers, but they must be 'glass-mat' types conforming to the ASTM standards.

Personally as a builder, I'm in 100% agreement with everyone else that one shouldn't EVER use any gypsum product as a tile backer in a shower, but personal preference aside and as a Code Official, it remains legal in most places in the US to either still use 'greenboard' or 'glass-mat' drywall for that purpose, and I would have to approve the use of greenboard or glass-mat gypsum if any builder or homeowner chose that method of construction.


01:32PM | 12/01/06
Member Since: 09/24/06
50 lifetime posts
Yes, I took those pictures of the shower in my new house when I moved in.

It's only fair to include the "After" pictures, however.

Funny thing was...the tile and drywall everywhere else was fine, but around the taps it was rotten.

The previous owner didn't use greenboard though...just plain drywall.

I redid my bathroom walls with Fiberock before I tiled.

Well, anyways, looks like I'm outnumbered. Greenboard is out. What about the Fiberock that I linked to?

All the specs on the MFR webpg indicate that you can use it in bathroom showers, and there are even instructions on how to put it up in a shower.

I don't want to argue either...I just want to learn. And I would like to think that I did my research fairly thoroughly before I put up the Fiberock.
50 you found my picture


01:33PM | 12/01/06
Member Since: 09/24/06
50 lifetime posts
After Fiberock and tile
51 after picture


03:29AM | 12/02/06
Member Since: 01/28/03
693 lifetime posts
Both USG's "Fiberock" and GP's "Dens-Armour" are approved for use in shower compartments and wet locations.

Both are approved by the American Society for Testing & Materials and the International Codes Council.

Various Fiberock products can even be used as structural wall sheathing, underlayment or interior sheathing in wet locations. Fiberock utilizes a combination of gypsum and recycled cellulose.

Dens-Armour/Dens-shield uses 'glass-mat' technology to reinforce the fiberglass sheets which remain mold resistant because unlike conventional drywall, both are 'paperless'.


08:01PM | 01/30/15
Hello, We are renovating our master bathroom and installing porcelain tiles on the shower walls. My contractor is going this route: 1) Studs 2) Greenboard 3) Kerdi (from Schluter) 4) Tile adhesive 5) Tiles 6) Epoxy grout. Is this the correct way to go, in your expert opinion? Thanks a lot.

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