Green Board or Wonder Board or Both

[JONES199]

Working out a budget for a small basement bath; owner takes "very long very hot showers", the entire room will be tiled (walls, ceiling, floor) with 18x18 ceramic tile. Do the walls / ceiling need to be covered with cement board or green board or both? The room is tight so if one was possible it would be preferred.

[mbyrne]

Re: Green Board or Wonder Board or Both

Jones199:
Since you have not filled out your profile, I am going to assume that you have been asleep for the past five years or have never installed tiles before.

If you are considering greenboard, why not just use cardboard since the tile industry does not even list greenboard among the materials that are suitable for tiling? (Actually that was a joke answer, I really don't suggest you use cardboard.)

How do you intend to provide slope with 18-inch tiles?

Most backerboards let water pass through so you will need to provide waterproofing. Owner takes a lot of "very long hot" showers? I suggest you use a surface-applied membrane instead of minimum-duty plastic film or tar paper behind the board.

It is obvious you need to purchase a TCNA Handbook so you can at least get a grip on some basics (www.tileusa.com).

Do you plan on installing a shower pan?

[JONES199]

Re: Green Board or Wonder Board or Both

As stated in post; I am preparing a budget, I am not a tile guy; my tile guy is away for a while, or I would ask him. Sorry I thought I could just post a simple question here so I coud finish my scope of work for the rock quote. Odd response for a moderator.

[inkster]

Re: Green Board or Wonder Board or Both

only one layer of board is needed.Use Cement Board or other suitable Backer board (theres about 6 options) Green Board is not one of them.What Michael was getting at is theres alot more to it then just the board,slopes membranes ect,ect. also need to be incclcudedin the scope of work.The 18" tiles are almost impossible to use on the floor,the create a slip hazard do to lack of grout joints and can nt be fit in around the drain slope.(without cutting them down in size.

[Dick Seibert]

Re: Green Board or Wonder Board or Both

I don't think there is a budget application when the owner takes "very long very hot showers". Best to do as Mike says and apply a waterproof membrane, like Vycor, then use mud and not either of the products you reference. You're talking about an installation which should follow "steam room" guidelines.

[Toolwhore]

Re: Green Board or Wonder Board or Both

mbyrne;

Be careful how you reply to people on this forum. The moderator will tell you to go pound salt up your butt!
Oh....that would be you, wouldn't it.
Never mind. ;-}

[mbyrne]

Re: Green Board or Wonder Board or Both

Dick:
One of the biggest problems with steam showers is created when the "waterproofing" is placed behind the mortar bed (or cement backer board). This type of membrane gets punched full of holes which allow water vapor to pass through into the stud wall cavity and beyond. as well, it is almost impossible to tie the membrane to movement joints around the showerhead, sprays, valves, etc.

Since I started attaching a load-bearing membrane on the setting bed surface, I have had no problems with any steam unit.

[Dick Seibert]

Re: Green Board or Wonder Board or Both

Mike:

What do you mean by:

load-bearing membrane on the setting bed surface

I use Bituthene and nail expanded metal lath with button nails. The plumbing penetrations have been my biggest source of failures in all showers, steam of otherwise. Since DuPont came out with Flexwrap I've been tightly wrapping the Flexwrap around all plumbing and lapping it shingle style under and then over the Bituthene. BTW, I won't touch their Tyvek, but I love their Flexwrap.

[Robert Z]

Re: Green Board or Wonder Board or Both

Dick,

Michael is referring to the types of waterproof membranes that you and I argued about several years ago.

[mbyrne]

Re: Green Board or Wonder Board or Both

Load-bearing membranes for tiling have been available for 20 years or more. I don't think I need to explain them here.

[Toolwhore]

Re: Green Board or Wonder Board or Both

OK, I've been following this thread and I would like to know what a load bearing membrane is also. I've installed tile before, but never in a steam shower. What was wrong with Dicks question? I thought you wanted any and all questions answered on this forum. If an explanation is too much, for whatever reason, how about an example or point us in some direction where we can find the answer.

[dgbldr]

Re: Green Board or Wonder Board or Both

Tom, from CTIA:

In 1993, American National Standard For Load Bearing, Bonded, Waterproof Membranes For Thin-Set Ceramic Tile and Dimension Stone Installations was adopted as ANSI A118.10-1993. This is an industry standard for a material that performs both as a slip sheet and as a waterproof membrane.

Read more here: http://www.ctioa.org/reports/fr56.html

DG

[Dick Seibert]

Re: Green Board or Wonder Board or Both

Rob's response indicates that the term "load bearing membrane" refers to a sealer applied on top of the mortar bed, I have to wonder where the term "load bearing" came from in that application? In construction/engineering the term "load bearing" refers to say a wall which carries a load, as opposed to a non load bearing wall which carries no loads down to the foundation.

As Rob and I discussed a few years ago, there is an issue here with sealers on top of the mortar bed, code now calls for a waterproof membrane behind the substrate, the application of a sealer on top of the mortar bed creates a double membrane, sealing moisture inside the substrate. Rob and I dropped the argument for two reasons:

1) His installations on the east coast didn't require a membrane behind the substrate, allowing the walls to dry out.
and
2) Rob says the newer "sealers" (and I presume "Load bearing membranes") now breathe, apparently having a permeability sufficient to allow moisture in the substrate to breathe in, while blocking the intrusion of liquid water.

In the 40s we put no membranes behind the mortar beds, we allowed our shower walls to breathe out, but now we need at least vapor retarders because we have codes, insulation in walls, and plywood sealing the moisture inside the walls. I use Vycor (or some Bituthene like product) to waterproof behind my mortar beds, Mike has said he uses a roofing type membrane to seal behind his mortar bed, I would not take the chance that a sealer of any type is actually going to breathe and allow the moisture to dry back inside the shower. A tile wall has to either dry in, or dry out, if code and the construction of the wall mandate that the tile wall dry in, then any sealer involved must be permeable enough to allow that to happen. Double barriers are never appropriate, they trap any moisture which gets in there.

I would like more information on exactly what a "load bearing membrane" is, especially a manufacturer's specification, then I can check out the permeability of such a membrane, and hence the appropriateness of such a membrane.

[dgbldr]

Re: Green Board or Wonder Board or Both

Dick,

If you will click on the link I gave just above your post, it should answer all of your questions. Every major setting-products manufacturer, such as Custom, Laticrete, etc. makes at least one such load-bearing membrane, plus Noble and Schluter. Visit their sites for data sheets.

DG

Edit: In this context, load-bearing is a correct term, and it is NOT a load perpendicular to the substrate, but parallel with it, except at corners.

[Toolwhore]

Re: Green Board or Wonder Board or Both

dg;

Thanks for the link.