# Type of material to use in tub area



## oh'mike (Sep 18, 2009)

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.


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## Bud Cline (Mar 12, 2006)

> 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.


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## Blondesense (Sep 23, 2008)

Ciperez said:


> 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:http://www.diychatroom.com/blogs/confused-about-constructing-shower-walls-152/
http://www.diychatroom.com/blogs/confused-about-constructing-shower-walls-152/


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## chrisBC (Dec 28, 2010)

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.


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## Bud Cline (Mar 12, 2006)

> In some areas greenboard itself is still used, *and is not against codes.*


*Au contraire my Canadian friend au contraire.
*

GREENBOARD IN SHOWERS
*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.


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## chrisBC (Dec 28, 2010)

: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.

cheers


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## Bud Cline (Mar 12, 2006)

> 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.


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## Marvel (Sep 22, 2011)

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


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## jeffnc (Apr 1, 2011)

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.


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## Bud Cline (Mar 12, 2006)

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.


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## jeffnc (Apr 1, 2011)

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.

http://en.wikipedia.org/wiki/Water_resistance


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## Bud Cline (Mar 12, 2006)

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!


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## chrisBC (Dec 28, 2010)

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.


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## jeffnc (Apr 1, 2011)

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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## oh'mike (Sep 18, 2009)

jeffnc said:


> . You can use drywall or plywood or whatever you want that's sturdy enough to hold tile.



Welcome New Guy---As pros we try to give advice that is 'best practice'

And 'code' 

We back up our advice with years of experience along with education like the teachings of the Tile Council of America..

You suggestions of drywall violate code in the United States---
And the suggestion of plywood goes against the accepted practices and the research done by the TCNA.

So please learn before you teach---Mike---


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## jeffnc (Apr 1, 2011)

oh'mike said:


> Welcome New Guy---As pros we try to give advice that is 'best practice'
> 
> And 'code'
> 
> ...


Get up to speed Mike and try to pay attention to context. I have no doubt you're going on years of experience, but you need to keep up to date with modern techniques.

I was just at the TCNA in Clemson not long ago, so this is straight from the horse's mouth.

Kerdi over drywall is to code and accepted by TCNA and recommended by the manufacturer (manufacturer directions trump code in most cases anyway).


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## jeffnc (Apr 1, 2011)

oh'mike said:


> And the suggestion of plywood goes against the accepted practices and the research done by the TCNA.


I stick with drywall, but I do take back putting Kerdi over plywood. I was thinking of Ditra when I wrote that, and just typed too quickly. Plywood is not dimensionally stable like cement board or drywall. This is fine under Ditra since the Ditra corrects for that - Kerdi can't.

Again, it makes more sense to put tile over Kerdi over drywall than over cement board. Completely code approved, TCNA accepted and manufacturer recommended.

Putting the waterproofing barrier behind cement board, as the poster wrote that I was responding to, makes no sense.


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## oh'mike (Sep 18, 2009)

I will admit that Schluter and the TCNA accept that Kerdi over drywall is accepted by both.

That still doesn't change my statement--The use of drywall and green board is still against code in the U.S. 

By the way,I was paying attention and I'm to old to get up to speed.

Your advice will cause a failure on an inspected job in the U.S. until the day the code is changed.


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## jeffnc (Apr 1, 2011)

oh'mike said:


> I will admit that Schluter and the TCNA accept that Kerdi over drywall is accepted by both.
> 
> That still doesn't change my statement--The use of drywall and green board is still against code in the U.S.
> 
> ...


No, it's not against code.

Keep 2 things in mind.

1) Manufacturer's instructions trump codes in most cases, and this is no exception.

2) Technically, it does not violate the code as written even without taking into consideration manufacturer's instructions. Drywall is not allowed in wet areas. The area behind a Kerdi membrane is not a wet area any more than the outside of a copper pipe is a wet area or the outside of a Romex cable is an electrically energized area.

An inspector might fail a Kerdi installation over drywall, but an inspector might fail any other number of things that are correct and best practices as well. This does not mean it's not to code, it just means the inspector is wrong. And you are definitely wrong that it will not pass the inspection, because it obviously has passed many times. Maybe in your experience it has failed, which is beside the point of whether it's a best practice or allowed by code.

See also this thread.
http://www.johnbridge.com/vbulletin/showthread.php?t=47133


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## chrisBC (Dec 28, 2010)

Both the membrane over drywall and cement board method are pretty bombproof, IMO. 

Putting cement board over a barrier is proven and works, i've taken apart a few rotten bathrooms and never seen a scenario where rot was found behind cement board. 

so hey what do you guys think about denshield backer board?, manufacturer installation says it doesn't require an additional barrier behind.


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## jeffnc (Apr 1, 2011)

JazMan said:


> Then in #16 you mistakenly said it's OK to Kerdi over plywood.


I was thinking of Ditra when I said that and have already corrected. Did you miss it or intentionally ignore it?



JazMan said:


> You then criticized Mike for saying that wallboard is not allowed in wet areas in the USA. (He is right) You responded by adding Kerdi over wallboard was OK.


No, we've been talking about Kerdi all along. I responded to a poster who talked about putting it behind cement board. I said it belongs in front, and once you do that you can even use drywall. Mike started arguing with that.


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## JazMan (Feb 17, 2007)

> I was thinking of Ditra when I said that and have already corrected. Did you miss it or intentionally ignore it?


I didn't miss anything. Everyone knows you corrected yourself later. Seems to me it would be second nature for a tile setter to know plywood in wet areas is not a recommend method. It is to me at least.

When you tell us we can use regular plain drywall in a shower IF it's covered by Kerdi, you are not telling us anything we didn't know 15 years ago or longer. But thanks anyway since ur new.

Jaz


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## jeffnc (Apr 1, 2011)

JazMan said:


> I didn't miss anything. Everyone knows you corrected yourself later. Seems to me it would be second nature for a tile setter to know plywood in wet areas is not a recommend method. It is to me at least.


Me too. Have you ever misspoke?



JazMan said:


> When you tell us we can use regular plain drywall in a shower IF it's covered by Kerdi, you are not telling us anything we didn't know 15 years ago or longer.


Really? Us? So you're speaking for your whole "team" here then? So then maybe you can tell me why there's an argument about it.


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## oh'mike (Sep 18, 2009)

We aren't a team--Jaz and Bud set me straight on a regular basis---We all 'misspeak' now and again.

And I thank them both when they do.

The bottom line for me is getting good sound advice to a member----If I'm wrong I want to know.--Mike---


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## chrisBC (Dec 28, 2010)

wow, this is getting boring fast, someones a little argumentative:whistling2:

anyways, i'm curious what ended up happening with the OP and the contractor putting up greenboard.


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## jeffnc (Apr 1, 2011)

chrisBC said:


> Putting cement board over a barrier is proven and works.


I'm not really convinced. You've got a situation where a porous, wicking type of material is attached to a membrane with screw holes piercing it. Seems to me this is pretty similar to leaving exposed nails on a shingled roof. Different, but similar.


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## chrisBC (Dec 28, 2010)

jeffnc said:


> I'm not really convinced. You've got a situation where a porous, wicking type of material is attached to a membrane with screw holes piercing it. Seems to me this is pretty similar to leaving exposed nails on a shingled roof. Different, but similar.


I see your point, however I'm not sure it will lead to anything major. What happens if the membrane over the drywall develops a leak? As I was saying, i've taken apart rotten bathrooms, and I have yet to take one apart that was done with cement board. If I come across a bathroom where the framing is completely rotten, and the cement board was installed properly with a barrier, then I might change my mind. I guess time will tell. At any rate, I think either method is highly superior to drywall/greenboard with tiles set right on top.

I'm still curious what everyone thinks about denshield backer board. The manufacturer claims that the waterproof membrane is built in, no need for an additional one. Also instructs to set the screws flush, not to countersink. I'm not a bathroom specialist and don't do them too often, so just curious what the tile/bathroom people think.


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## Gary in WA (Mar 11, 2009)

Moisture-Wick Testing

DensShield Tile Backer and the leading brands of cement
board were subjected to wicking tests according to the
Ceramic Tile Institute test procedures CTI-T83. The tests
showed that within a 24-hour period, cement board will
wick at least 3 up the board while DensShield will wick
less than one-third of 1” (.319) during that same period.
From: http://docs.google.com/viewer?a=v&q=cache:w1AJ6TtrhyUJ:www.gp.com/build/DocumentViewer.aspx%3Frepository%3DBP%26elementid%3D6876+water+wicking+of+Hardie+backer+board&hl=en&gl=us&pid=bl&srcid=ADGEESgQJOopeO3wUmdj4zlyJEPKDmoWjxfx5yBhv0p_go659HiYh7B7Wq5otHvQZQMt6mYFbx9Qr5ieMsQrG9lgqmlZT5DyC8Wtgw7lAUIKPiHUH_UsVshTK162kZ6HujkunZUHPD96&sig=AHIEtbRqwCDcu8AJUye5WlK87HmnplLw0w

Fiberock and greenboard are not allowed per some codes: http://www.jameshardie.com/pdf/backer-comparison-half.pdf

DUROCK is water durable and moisture, mold resistant: http://www.usg.com/durock-cement-board.html

“Q: What is the difference between DensGuard tile backer and cement board or fiber-cement board?

A: While cement-based backer boards are *water-durable* they *do not contribute* to proper moisture management. In order to prevent the passage of moisture into the tile assembly the Tile Council of North America requires the use of a membrane to block the passage of moisture, since both the wall cavity and the floor substrate are susceptible to moisture damage. DensGuard tile backer has a built-in moisture barrier on the face which protects the wall cavity and floor substrate. It is at least 30% lighter than leading cement-based boards and has a non-abrasive, moisture-resistant core. Cement board has a heavy, crumbly, abrasive core, which can scratch tubs and fixtures. In addition, unlike cement-based backers, DensGuard backer board does not require any special tools or fasteners to cut and install.”---- from: http://www.gp.com/build/faq.aspx#faq_10360

Ciperez, are you installing tile directly on the greenboard?

Gary


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## jeffnc (Apr 1, 2011)

chrisBC said:


> What happens if the membrane over the drywall develops a leak?


Well, I've personally never seen a failure behind a Kerdi system. But then again, they're not used much in the grand scheme of things, and are relatively new to this country. But in talking to the guys at TCNA and Schluter reps, this is supposedly a problem.

I was told that if the membrane is pierced for any reason, either the Kerdi must be patched, or the hole must be waterproofed. For example if you screw your glass shower door into your shower curb through the Kerdi, you have to fill the hole with KerdiFix or equivalent before driving the screw.

They described a tile guy who used to use nails (actual 16d nails driven into the backer board substrate) to space his tiles. He wasn't familiar with Kerdi the first time he was hired to tile over it, and put his nails there too. This was described to me as a laughable disaster requiring all the Kerdi to be reinstalled. Those holes were on vertical surfaces and would be filled with thinset. Worse than screw holes through plastic I suppose, but still....

Maybe they're being overly cautious. This is not just Schluter reps covering their asses for warranty purposes though.


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