Tiling a greenboard ceiling in steam room

[Deirdre]

I would like some advice on tiling a green board ceiling within an enclosed steam bath. What is the best size tile to work with and what is the strongest adhesive or thinset to use. Also when grouting should any additive be used to ensure a proper seal is achieved.

[prashster]

Your best bet is to post this question on johnbridge.com. That website is dedicated to tiling. If you think THIS forum is great, you'll LOVE that one for your tiling questions.

One thing to think about: sure you want to do green board? Have you considered Schluter Kerdi? It's a waterproofing membrane that goes over reg drywall and it gets rave reviews from users.

As far as tile size: in general, smaller tiles (6x6 or smaller) will adhere easier than larger ones on a ceiling. Besides that, consider what fits easiest with minimal cuts, and what looks good to you.

[jimbo]

Yes, check with johnbridge. I think there are some restrictions about greenboard on ceilings, and there may be a recommendation for a better installation than greenboard in a steam room.

[jadnashua]

As of January 1st this year, greenboard is no longer an approved product for showers. Now, you local code may not have caught up with that. It never was a good thing, especially for a steam shower. You need an especially capable vapor barrier to protect the structure with a steam shower, and greenboard just doesn't cut it. Also note that greenboard on a ceiling must be supported at 12" spacing since it is subject to bowing under its own weight, let alone with tile on it. Basically, greenboard just isn't as dense, strong, or stiff as plain drywall. When you put a screw or nail through it, or on a cut edge, it allows moisture to reach the core, which negates anything that the unbroken moisture resistant surface coating could do.

Most places rely on the Tile Council of America's guidebook. This has very specific requirments for building a steam shower. Greenboard doesn't show up in it. Hopefully, this isn't already built with greenboard in it. The people over at www.johnbridge.com can help set you straight so you can have a product you are proud of and that will last.

Neither tile nor grout is waterproof. A good porcelain tile is nearly there, though. A sealer for the grout will help prevent water through and help keep it clean, but will NOT prevent vapor through. Moisture WILL get to whatever is behind the tile, so it must be able to withstand it. Greenboard with the penetrations and raw edges just can't handle it.

[geniescience]

Deirdre

I often tell people they are asking good questions. In your case these three questions you started with are not the best questions to ask. My opinon.

Any size tile will work. Any thinset will work, any grout will stick well (since it is mostly portland cement), and any thinset or grout among the better half (if measured by the cost as the only metric) will work so totally that no-one will be worried down the line.

Meanwhile, you haven't said how you got this far : - do you have greenboard on the walls? Is this a new steam shower or an old one? How is it insulated? And since you mentioned adhesive as opposed to thinset, does this mean you thought a mastic would work? It'll stick, but it won't be appropriate in a humid area. A steam shower ceiling is the most humid ceiling possible. How have you protected the shower with a vapour barrier?

Hope this helps. Most of what I have said above is confirmed at www.johnbridge.com The best questions involve vapour, insulation, and preventing cracking where walls meet floors and ceilings. My opinion.

(Edit: Everything Jim said above is true, and more)

[Deirdre]

Thanks for all the advice, I will also check JohnBridge. Wow I guess I should have done all this before putting up the green board. To answer geniescience's questions. It is a new steam shower I have constructed all the walls are clay block with a plastering of mortar these will be tiled as well .
I'm not too sure I can get the other product suggested in my country, but I can get a mapei cement board about 1/4 inch thick pretty heavy though or something called wonder board. Do you know any of these? It's not too late for me to change the green board but I want to ensure I use the right thing. Also on another web site they suggested using roofing felt before putting up the ceiling board, what do you think about that?

[geniescience]

Very solid. Walls of Clay block and mortar. Good!

Deirdre, is the floor built, finished? How?

Walls made of tile, mortar and clay block will act as a large rigid sponge soaking up humidity. Most users don't notice this and don't care much about this concern, but it is important. Depending on your climate and your building, this can cause serious problems for you, either for your health or the building's health. What Jim deB said about vapour barrier for the ceiling also applies to your walls. It is important to achieve "containment" and keep humidity inside the steam shower instead of letting it soak into the building's structure. Tiles alone will not be sufficient vapour barrier.

If you didn't know about vapour barriers in your ceiling, it is likely that the same applies to your walls.

Walls made of tile, mortar and clay block will act as a heat sink. Good to know, that's all. Any additional layer, thin, of any kind of insulator will help keep your heat inside the steam shower. Since people generally want their steam shower to be hot, that is why I am mentioning this to you. Any layer of anything not made of cement, clay or porcelain. Think membrane, like plastic, foam, etc. Think vapour barrier. A vapour barrier acts as a minor heat insulator too, as a secondary function.

What climate are you in? Tropical, temperate? Where you live, do builders all say vapour barriers are not necessary for steam showers?

David

[Deirdre]

Thanks David, Wow this is getting complicated, all I wanted was a simple steam shower. I live in the caribbean tropical climate over here we build very differently all structures are either concrete or clay block with a cement plastering to finish. Walls are never insulated and we are only now starting to insulate roofs to help keep the buildings cooler. I am renovating a 30 yr old house. the floors are concrete and tiled so I will be tiling over the exsisting tile. I have no idea how to insulate the walls at this stage seeing that they are already done in concrete. No one here really knows much about constructing a steam shower they are not at all common. what do you think about the roofing felt for the ceiling before the board? l

[jadnashua]

High humidity levels typical of your climate combined with high temp steam is a recipe for mildew...moisture is okay if it can breath, steam will force moisture where it normally wouldn't go, or at least deeper into the structure. Luckily, you don't seem to have too many items that mold thrives on (gypsum and paper are desert to mold). I'm not sure about plaster.

The biggest group of experts on this subject is over at www.johnbridge.com. Some of us frequent both places, but are not experts, just read a lot. Your situation suggests professional advice rather than guesses based on what others have said.

I have my ideas, but I strongly suggest expert advice.

[Mike50]

As of January 1st this year, greenboard is no longer an approved product for showers. Now, you local code may not have caught up with that. It never was a good thing, especially for a steam shower. You need an especially capable vapor barrier to protect the structure with a steam shower, and greenboard just doesn't cut it...(..)

Are you referring to the "wonderboard" and (other brand composite boards from tile dept. at Big box)?

[jadnashua]

No, greenboard...gypsum with the water resistant layer. I've heard of, but not used Wonderboard, so I can't comment. From what I understand, greenboard has been specified for damp areas, including shower surrounds and above tubs. National code now prohibits its use there. Some locals have not updated their codes to comply. My opinion, a good coat of primer and paint on regular drywall does as good or better than greenboard and is stiffer. Under conditions like in a ceiling over a shower, the manufacturer specs 12" support or you risk it developing bows. Doesn't happen all of the time, or necessarily right away, but the grain in the paper on drywall is stronger than that on greenboard.

If the area is likely to get wet, neither greenboard nor drywall is a good idea. By wet, I'm referring to direct spray on a regular basis, or an area where water might pool. A steam shower would put moisture everywhere, so that negates using either in my opinion.

The only expection I can think of is if you are using a membrane such as Kerdi from www.schluter.com. They specify using it directly over drywall in a regular or steam shower. It is waterproof, and is highly resistant to vapor pressure penetration.

[Mike50]

OK. Thanks..
I was talking about the gray stamped "Ceramic Backerboard".

[geniescience]

Deirdre,

Forget most of the above. In temperate climates, it is really important. Where you are it is less important. Neither concern is as critical.

In your building, do you regularly keep all the windows closed and use Air Conditioning?

David

[Deirdre]

No David in that particular room there is a window to the outside that is always open but the adjoining room is airconditioned with a door way and vent opening in the wall connecting both spaces.That a/c is used mainly at night. The steam is certainly not going to be used on a daily basis as in a commercial spa setting, it is for residental use.

Deirdre

[sulconst2]

hello all,


one thing about the ceiling in a steam shower is it should be pitched or the condensation from the steam will drip like rain. uncomfortable in a relaxing setting. i like using hardi-board instead of wonderboard. same properties but easier to work with. the kerdi i believe makes a mesh to tape joints and corners. then skimcoat with their "thinset" to waterproof before tileing. if doing a custom pan for the floor then you'll need a pitched membrane which is a whole new game.