Use cement backerboard. Greenboard is OK for regular walls in a bathroom (but doesn't really add anything that proper priming and painting would), but for a shower/tub surround, use cement backerboard. Greenboard is just regular drywall with a coating. If you want to be sure about things, put something waterproof like #15 building paper, then the cement backerboard, then the grout and tile.

I've been doing an experiment, with an interesting result.

Took a scrap of mositure resistant sheetwork (greenboard) and soaked it in a cup of water for two days. Hasn't shown a bit of deterioration. Regular sheetrock was like mud.

Because it's so much easier to use, I'm tempted to use the MR sheetrock. Will I regret it in 20 years? Both materials have their advantages. Tough decision.

Go post your question on the bathroom forum or do a search on the bathroom forum. A couple of professional tilers hang out there and can give you an answer or if you do a search you can find an answer already posted. Great forum, bathrooms, found online source for bath fans cheaper than Lowes.

"Took a scrap of mositure resistant sheetwork (greenboard) and soaked it in a cup of water for two days. Hasn't shown a bit of deterioration. Regular sheetrock was like mud."

Are you building a swimming pool or a bathroom wall?
If you have that much moisture around you are going to have a lot of other problems.

A coat of primer and two coats of paint will provide a barrier for the walls in a bathroom not inside a shower or over a tub.
The wax coating on greenboard comes with its own set of problems with paint adhesion and moisture movement. Once the moisture gets in it is very hard to get it out.

The plumbing codes prohibit using water reaistant sheetrock in the shower enclosure area.

Code requires a water resistant membrane such as housewrap on the studding then apply concrete baskerboard until the walls reach an elevation of 72" above the finished drain.

There is a variation that is being used in some areas. They use water resistant gypboard with a Kerdi Membrane however it requires written approval of the local inspector.

Our house is only 15 years old, 2 years ago my son's bathroom shower tiles had a grout failure which was causing a leak down onto the ceiling below the bathroom. The whole tiled shower wall was bowing. We tore the tile down only to find green board that was mildewy and in bad shape behind it. So yeah, 15 years down the road, 13 in our case the greenboard in a shower won't be holding up for you. We replaced with cement backer board, which is the thing to use in this case.

Grouted and tiled walls are only 'waterproof' in the sense that waters does not damage the materials.
While the tile itself is very effective at stopping moisture movement, the grout is not. AS a cement product it wicks moisture very well, sealed, unsealed, with or without addatives, grout wicks water.
The wicking is why even cement board (that also wicks mopisture) still requires a barrier.
Tarpaper still works fine, and there are a number of newer products on the market also.
The barrier needs to extend allthe way to the shower base or tub rim, and end inside the lip. A path for the water that WILL work thorugh must be provided to prevent long term damage.

I have a job on a rental house right now that had all the bathrooms 'upograded' in about the 1970s with greenboard.
I can still see some of the remains of the mortar bed job that was torn out.
The tiles are falling off the walls now, and everything will need to be stripped out and replaced.
At this point a fiberglass insert is looking pretty decent for the owner since the house is a rental property.

Contrary to popular opinion, "greenboard is not regular GWB with a water-resistant paper finish; in addition to the special paper front and back, it has a water-resistant gypsum core.

Last year USG finally gave in to industry, code and mold lawsuit pressures and changed their recommendation for greenboard to:
"Perfect for use in areas such as bathrooms, powder rooms, kitchens, and utility rooms with incidental moisture exposure. Not designed for use in high-moisture areas such as tub and shower surrounds."
and

"Do not use in tub and shower surrounds; use DUROCK� Brand Cement Board for these applications."

The tile industry has considered greenboard an unsuitable substrate in wet areas (showers) since 1978 when the Tile Council of America stamped "QUESTIONED INSTALLATION IN WET AREAS" across the tub and shower details in their manual in red ink. That was about the time that Wonder Board, the first fiberglass reinforced concrete backerboard, was introduced.

I won an argument in 1980 with a builder on a 12 story luxury condo project in Minneapolis where the GC convinced the Owner that the Wonderboard I had specified was not worth the cost. The low tile bidder had included installation of Wonderborad in his contract which astounded the general contractor. When asked in the weekly job meeting why, the tile contractor said he believed it was cheaper to put Wonderboard in than to come back and replace the tile later.

If you are too lazy to use Durock at least put it in for the bottom 30 inches of the wall where the problems are most likely to occur.

If you use greenboard do not install it over a vapor barrier.

If there is a steam unit do not use greenboard or Hardiboard.

Here is a link that might be useful: USG moisture resistant GWB

Building code has followed suit as well.

With the last revision, IRC prohibits the use of greenboard as a tile substrate in wet (Shower, tub surround) areas.

Mongo

Some 6 years ago I installed a shower,at that time I never heard of any adverse opinion to using greenboard as opposed to any other product. Was I neglectful to my client to have used greenboard at that time?

Chuckling. Found a loose tile in shower went to repair it and had a domino effect on all the tiles coming loose. After demolition found contractor used regular gypsum board. Taking no chances . Fiber reinforced concrete backing will be used. The single tile ended up being a total remodel. Torn apart that far might as well upgrade.

"Contrary to popular opinion, "greenboard is not regular GWB with a water-resistant paper finish; in addition to the special paper front and back, it has a water-resistant gypsum core. "

So what.

It is still not, and never was, adequate for wet area tile support.

The tile industry NEVER recommended it for wet areas.
Wonder why?

I had a customer a few weeks ago cal because the entire tile wall the length of her tub fell into the tub.
Five year old green board.

The core was much less than solid.

Three people a day used the tub to take a shower.

mightyanvil is 100% correct.

~Jeana

Should I use backer board for my kitchen backsplash? Hubby seems to think we do but much of the advice I have heard on these forums say no. Is the kitchen a wet enough area to have this issue?

Ailsa

Completely unnecessary, as long as the drywall is in reasonable shape, not damp or missing its paper surface.

What do the manufacturers instructions call for the backer to be?

+1 I would default to the tile guidelines first. No reason that a backsplash in a kitchen should be getting that much moisture on it to require cement board though.

4 yr old thread workman

There was a question that I was responding to that was deleted by the poster, why I do not know. I would not respond to a 4 year old post unless it was with a smart*** answer like yours, lol.........

I was just curious, you seem to jump on others for that. Perhaps this nice holiday weekend will relax you a bit, but ez on the candy it makes you kind of pissy ill telluwhat.

You guys seem knowledgeable so I'm hoping for input. 4 years ago I had a tile shower redone. Now the shower pan has to be redone. Contractor today said it appears the guy used green board instead of cement board like he told me. This guy advises tearing out the entire thing since eventually it will go bad. He feels I'm wasting money by only doing the pan. There is no known problem with the green board right now, but it was not sealed with red guard so it's likely a matter of time. Since its double the price, is he right? Should I do it?

Interesting thread. I'm re-doing a 27 year old bathroom. I've removed the original fiberglass tube / shower and headed towards an Onyx walk in shower, but first I need to replace the wall that was behind it. This USG Durock material looks interesting for that application. But I have a related question. I'm also refinishing the ceiling and walls. There have been some mold spots on the ceiling in the past, particularly in the vicinity of the exhaust vent and I'm wondering what I should do there. Currently it's finished (standard) drywall with just semi-gloss paint. Above that is heavy plastic sheet and then cellulose insulation, so removing it is really undesirable. I realize that double vapor barriers are generally undesirable but still wondering if a brush on anti-mold treatment then a layer of this Durock material over the existing ceiling would work. Comments ??

How does densashield compare to the durock?

Denseshield is waterproof, durock isn't, unless its the new waterproof system by USG

My issue is a bit different. I am dealing with a 20% moisture content concrete subfloor due to being in a hot springs district. In pulling up the old carpet, I find 3/4" particle board (!) (stained and some crumbling) and am wondering if I should replace that with 3/4" greenboard or do I need to upgrade to cement board (Durock?) or just put down more particle board before laying down the click-lock laminate wood flooring I've been using successfully for 5 years now? AND, I need to put a moisture barrier under the laminate (at least I always have in the past) so does this still go over the greenboard or cement board? And if using greenboard, which side of that do I place face-down against the sometimes moisturous [sic] concrete subfloor and which one up? I understand I shouldn't trap moisture in with TWO moisture barriers so am wondering how best to deal with this situation. Thanks!

I would definitely incorporate a moisture barrier and possible that vented floor sheathing that allows the surface to dry out.

I would be highly suspect of any substrate that is moisture sensitive.

MR board is not rated for flooring use

I don't know of any drywall that is 3/4" thick nor should drywall be used as a flooring underlayment as already mentioned.

If the concrete is dry to the touch, cover it with self adhering Grace Ultra butyl waterproofing membrane rolling all of it with a steel roller. Then mechanically attach Durock, then install the laminate flooring without a vapor barrier.

You could use Ice & Water Shield but it has an asphaltic odor.

Just a comment on this 10 year old post, but about 10 years ago, I had the same problem that the OP had - failed drywall causing tiles to fall in. I used cement board around the tub and shower and green board everywhere else. I didn't find the cement board much more difficult to use than the green board (or any other drywall) so I don't see what the OP's objections to it are.

An interesting aside, this bathroom was not original to the house. The non-shower side of the room had been a closet wall (not a bathroom wall). I removed the "drywall" which turned out to be a gypsum board based lath 3/4" thick with plaster over it. On the back of the gypsum board was printed "patented 1885". The house was built in 1890. A cross section showed three layers of plaster between thin sheets of paper.

Contractor wants to use green board drywall with schulter membrane in shower area. Would you recommend using cement board or allow to use the drywall + mesh defense?

You can install Schluter over drywall. I'd use the cement board just in case that was ever a leak though.

Schluter Kerdi OK over drywall not MR green board if I remember correctly. I would use cement board anyhow.

Greenboard or MR board has a waxy coating not good for Kerdi fabric.

C&R Thanks for confirming. Now JK Kuzenka needs to wonder how knowledgeable their contractor is.

Thanks!