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Ciperez 11-01-2011 07:24 AM

Type of material to use in tub area
My contractor put in green board in tub area. It will be tiled. I told him
that is not proper material. I've seen a grey colored
material used on tv. What should he use?

oh'mike 11-01-2011 08:11 AM

Cement backer board is what you want--google--Durrock or Hardibacker.

There are others,also including a fiberglass covered product---

Green board has not been allowed in wet areas in many years---in the USA any way.

Look for a Blog by Bud Cline--Preparing a wall for tile.

Bud Cline 11-01-2011 09:19 AM


My contractor put in green board in tub area. It will be tiled. I told him
that is not proper material. I've seen a grey colored
material used on tv. What should he use?
Bad idea!
You should stop that progress and reject the green-board in a shower.
Not at all the correct material to be used in a wet area.
Either the contractor is not up on standards or he just doesn't care and is looking for a path of least resistance.

Blondesense 11-01-2011 12:06 PM


Originally Posted by Ciperez (Post 761309)
My contractor put in green board in tub area. It will be tiled.

What do you mean by "tub area"? If it is a tub/shower combo listen to Bud and Mike. No greenboard unless there is Kerdi involved.
If it is a tub only, greenboard may be allowed, but cement board would be better.

Bud's blog:

chrisBC 11-04-2011 12:01 AM

The greenboard will be fine if used with a waterproof material over it, Kerdi, etc. Check with your local inspector/codes though.

In some areas greenboard itself is still used, and is not against codes. If it's not maintained properly, it will be damaged by water. If it is not against code in your area, then legally it is acceptable, however not advisable. What i'm trying to say is if this wasn't specified before work started, and is not against code, then it's not that your contractor used the "wrong" product, just not the best/up to date product. Since this wasn't specified from the beginning, you will have to work this out with him. This is why I always specify materials to be used before starting work. At least it's not tiled yet and won't be huge deal to put in a different product, or apply a membrane over.

I have taken apart bathrooms with greenboard (or drywall) directly under the tile. Some have been rotten and mouldy, others have been that way for 25 years plus, and have had no mould or deterioration whatsoever. Depends on the maintenance I guess.

I usually use denshield tile backer board for this application. I believe the kerdi is somewhat expensive, however may be a less expensive option than replacing the greenboard.

Bud Cline 11-04-2011 09:53 AM


In some areas greenboard itself is still used, and is not against codes.
Au contraire my Canadian friend au contraire.

The International Residential Code (IRC) has determined that effective January, 2006, paper-faced greenboard will no longer meet its standards as an approved tile backer substrate for wall tile in wet areas such as tub and shower areas.
IRC, Chapter 7 - Wall Covering
R702.3.8 Water-resistant gypsum backing board. Gypsum board used as the base or backer for adhesive application of ceramic tile or other required nonabsorbent finish material shall conform to ASTM C 630 or C 1178. Use of water-resistant gypsum backing board shall be permitted on ceilings where framing spacing does not exceed 12 inches (305 mm) on center for 1/2-inch-thick (13 mm) or 16 inches (406 mm) for 5/8-inch-thick (16 mm) gypsum board.
Water-resistant gypsum board shall not be installed over a vapor retarder in a shower or tub compartment. Cut or exposed edges, including those at wall intersections, shall be sealed as recommended by the manufacturer.
R702.3.8.1 Limitations. Water resistant gypsum backing board shall not be used where there will be direct exposure to water, or in areas subject to continuous high humidity.
R702.4.2 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 manufacturers’ recommendations shall be used as backers for wall tile in tub and shower areas and wall panels in shower areas.

chrisBC 11-04-2011 10:47 AM

:thumbsup:Thanks Bud, interesting

I never use it myself, however I see it around often enough I guess I "assumed" it was still widely used, although not popular.

How about if it is covered by kerdi or another membrane?, i'm sure i've seen this done.


Bud Cline 11-04-2011 11:14 AM


How about if it is covered by kerdi or another membrane?, i'm sure i've seen this done.
Yup ! That technique is allowable.

In fact, Schluter KERDI Schluter DITRA and Schluter DITRA-XL were evaluated by an independent evaluation service in a most recent published report dated August 1, 2011 and were found to meet compliance with:
2006 International Building Code (Commercial Construction)
2006 International Code (Residential Construction)
2006 International Plumbing Code (All Construction)

KERDI was found to be suitable for use over (among other things) "Gypsum Board".

I have the reports but I'm not sure I should be the one to post them here. The reports are subject to renewal in two years.

Worth noting is there are other similar membranes on the market but I'm not familiar with their "code status". I'm sure that in the case of similar products offered by Noble Company theirs are Code Compliant also.

Marvel 11-04-2011 02:45 PM

Bud- We are not worthy!!! Keep up the good work.

jeffnc 11-07-2011 10:54 AM

IMO, tile over Kerdi over drywall is better than tile over cement board. Why? Because cement board is water resistant, not waterproof. That means the cement board can get wet with no damage, unlike drywall. But why let anything get wet? If the cement board gets wet, so can the studs and joists, and we definitely don't want those getting wet.

In this day and age, why on earth not waterproof? I don't think I've ever taken a bathroom apart without seeing at least a little water damage, and often a significant amount that needs some real carpentry/structural work.

Kerdi over cement board is fine too, but why bother with that? No water is touching it. Costs a little more and is harder to work with.

Bud Cline 11-07-2011 01:06 PM

Cement board is actually NOT WATER RESISTANT. It will not resist water. Other than that the above information can be considered up to the minute.

When cement board is used without a waterproof coating on the surface it requires a moisture barrier on the studs for just that reason. Because it will wick water long before it will ever resist it.:)

jeffnc 11-07-2011 01:52 PM

You must be using a narrow connotation of water resistance. Consider what cement board does, then consider the meanings of water resistance and the context of my comment. And consider that I specified exactly what definition I was using. Cement board is water resistant.

Bud Cline 11-07-2011 02:48 PM

Not going to argue but also not going to agree that cement board "resists" water because it does not.

If you know anything about Wikipedia then you know that entries there can be written by anyone that cares to take the time to do it. If you also take a closer look at the Wikipedia offering you make then it is easy to see that that person lacks a command of the English language and it was probably written by someone with an eigth grade education.:yes:

I stroked you for the remainder of your information in an effort to avoid exactly what has happened here anyway.:whistling2:

Giving up now!:)

chrisBC 11-07-2011 03:39 PM

My understanding is that cement board is "waterproof" meaning by my defintion, that it will not rot or deteriorate when wet. However it will probably get wet- so that is why a barrier is used behind the board.

jeffnc 11-07-2011 05:37 PM

It would make more sense to put a barrier in front of the board. If you put the barrier behind it, it will be pierced by screws when the board is installed. And once you put the barrier in front of it, the barrier no longer needs to be water resistant or waterproof or anything. You can use drywall or plywood or whatever you want that's sturdy enough to hold tile.

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