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Greenboard or Cement Backer for Tub/Shower?

Posted by walrus (My Page) on
Thu, Jan 25, 07 at 22:31

Need to replace a tiled wall behind a 5' tub with a shower.

It was built circa 1970, and the installer used conventional sheetrock with 4X4 ceramic tiles. It's rotted out because of small cracks in the grout at the base of the wall.

Should I use moisture resistant sheetrock or the cement backer board behind the new tiles? The moisture resistant sheetrock would be a lot easier for me to put in.


Follow-Up Postings:

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RE: Greenboard or Cement Backer for Tub/Shower?

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.


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RE: Greenboard or Cement Backer for Tub/Shower?

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.


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RE: Greenboard or Cement Backer for Tub/Shower?

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.


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RE: Greenboard or Cement Backer for Tub/Shower?

"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.


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RE: Greenboard or Cement Backer for Tub/Shower?

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.


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RE: Greenboard or Cement Backer for Tub/Shower?

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.


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RE: Greenboard or Cement Backer for Tub/Shower?

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.


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RE: Greenboard or Cement Backer for Tub/Shower?

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.

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


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RE: Greenboard or Cement Backer for Tub/Shower?

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


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RE: Greenboard or Cement Backer for Tub/Shower?

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?


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RE: Greenboard or Cement Backer for Tub/Shower?

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.


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RE: Greenboard or Cement Backer for Tub/Shower?

"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.


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RE: Greenboard or Cement Backer for Tub/Shower?

mightyanvil is 100% correct.

~Jeana


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RE: Greenboard or Cement Backer for Tub/Shower?

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


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RE: Greenboard or Cement Backer for Tub/Shower?

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


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