I hope it's okay because I just ordered honed limestone tiles to do the floors in two bathrooms we are remodeling! I will admit that I didn't do a ton of research on limestone though. I have seen it in a lot of magazines so I figured it would be okay :-). I did leave a cut lemon on a sample tile and it didn't etch (honed tile). I let a drop of wine sit on it for a awhile then just wiped it off and it left the very faintest mark. I really don't think the floors will get much spilt on them other than water. Our contractor just said in a bathroom to keep it sealed well or it can get smelly? Our two bathrooms are small so keeping the tiles sealed should not be that much work. We are beginning demo soon so I can let you know!

Hi jenny, i think limestone in a bath is ok in general. i currently have travertine in my bath and it has held up fine. cleaning is a little more difficult in that you have to watch what products you use. i think our toilet bowl cleaner etched it a little bit, but it is not too noticeable..

the issue i have heard is that for steam showers, specifically, it is better not to use porous materials. so i was wondering if it would be bad for th floors and a little bit of the background on the walls.. i recall reading that marble especially is bad, but am not sure why.. would love it if someone with a steam shower could let me know?
thanks!!

Limestone should not be used in any shower. It's too porous and will be extremely difficult to clean. Using it for a tub only surround or flooring would be OK as long as you keep it sealed and don't spill anything acidic on it.

livewireoak, i was hoping that wasn't the case. boo hoo.
i guess i will try to find some good limestone lookalikes for the shower.

i have heard any natural stone is best not used in a steam shower. that said, i'm redoing our master bath and it will have steam. i selected porcelain tile floor and walls, but a marble mosaic for a decorative panel - that's it for natural stone.

hi phylhl, thanks for the info. yeah, i guess it would be too problematic to use natural stone, so i have resigned myself to just go with tile but maybe will do a natural stone top for the seat in my builtinbench.. what tile are you using? would love to see pics!

As I understand it, the reason you don't want to use natural stone for steam showers is because the stone is porous which means that the water vapor will penetrate the stone ending up behind it, and causing water/mold problems in the future. I don't know that sealing the stone solves that problem - sealing protects the stone from stains, etc., but I don't think it will deal with the water vapor and drying that water which is a serious concern.

What water-proofing membrane are you using behind the tiles? You'll definitely need something to prevent water damage.

michoumonster - we are using granite for the bench seat. I just today selected the grout and the grout being used is antimicrobial and stain resistant - plus it will be sealed which I'm told is fine to do but not necessary with this grout. We will be using Tec grout with Grout Boost (floors) and Laticrete Permacolor on the walls (in bright white) which also is stain resistant and antimicrobial.

ae2ga, thanks for the explanation on why not to use natural stone. i think it makes sense. I will make sure we use a vapor barrier behind the tiles too.

phylhl, thanks for the details on what grout and sealer you are using. I will look into those brands also and see if they can be used with the tiles I am choosing. Sounds like you are in the home stretch now. Hope to see pictures of your bath soon!

Mm- no problem. Please check to be sure but I think a vapor barrier and water proofing are two different things. A vapor barrier goes under the concrete backerboard and water proofing goes on top of it. I think (please don't quote me) that vapor barrier is code required and water proofing (a product like kerdior hydroban) is not. However, waterproofing is greatly beneficial, especially in a steam shower application.

Good luck - I look forward to seeing pictures.

p.s. the portion below is from the thermasol website:

1. Prepare the ceiling for steam.
You will need to add a slope to the ceiling of the shower area. Your standard shower ceiling will not drain properly if the ceiling is flat. Water will condense and drip down on you as you take your steam shower distracting from the steam experience if not ruining it entirely. It will also stay in damp spots on the ceiling because it has no slant to drain it off to the wall.

2. Prepare the walls for steam.
   Start by going down to the wall studs and stapling 6 mil plastic across them. Add the concrete backer-board, which is the basis for your tile. When you put it on, make sure to put mesh tape on the seams and seal them with thinset.
   Add a rubber membrane to the backer-board. You can get this in sheets, but the easiest way to install the membrane is to use a liquid polymer roll-on type membrane. The roll-on kind gives you a very watertight seal if you apply it correctly. Follow the instructions on the container.
   Use tile and grout, or stone and a special sealant for the stone. The final step in making you steam home shower watertight is sealing around all the fixtures once you have them in place. Your shower room floor should be waterproof and have a functional drain.

Our cement backer board is now up. How do I know if the 6 mil plastic went on first?

Ask the folks that put it in? Or, you might try liiking into the hole where the diverter is....

Just for clarification...

Confusion can come from the fact that not all waterproof barriers are vapor barriers.

In a steam shower you need a vapor barrier. In a non-steam shower, you can use a waterproof barrier or a vapor barrier.

In a steam shower I prefer a topical vapor barrier/membrane, one that goes on the face of the tile backer board. Kerdi and RedGard are two that will work in a steam shower, they'll provide all the protection you need.

Do understand that Hydroban is a waterproof barrier but not a vapor barrier. So Hydroban is an excellent choice for showers, but is not appropriate for steam showers.

If you are going to use a topical vapor barrier like RedGard or Kerdi (or one of the Nobel products, etc), then you do not want to use another barrier (like 6-mil poly) behind the cement board.

To be honest, 6-mil poly is sort of difficult to detail in terms of getting a complete seal. In a steam shower you want all six sides of the shower "cube" to be fully sealed with the membrane. I personally prefer to use Kerdi in steam showers. Not a sales job. Just what I prefer.

And the advice to not use a porous stone like limestone is good advice. Vapor can be driven into porous stone, and if the stone has any iron deposits in it, they can oxidize or "rust", giving a yellow/orange/brown hue or a splotchy staining look to the stone. Here's a generic photo of a marble bench in a steam shower:

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This topic is very confusing indeed!

One question about kerdi vs redguard - do either have a compatible barrier product that will be good on inside and outside corners of a niche? Can either product be applied over hardybacker cement board? which would be preferable in this application?

thanks for beginning to clear this up. still clear as mud but getting better....

Kerdi is a sheet membrane. They do have manufactured inside and outside corners.

There are some Kerdi photos here.

RedGard is a liquid membrane that you can trowel, roll, or brush on the wall. You might need reinforcing fabric at the niche corners to cover gaps and allow the membrane to bridge the gaps.

Either can be applied over Hardie. I usually use cement board like Durock or Wonderboard instead of Hardie. I have used Kerdi over Hardie with no issues, although some DIY posters have had difficulty with Hardie wicking water out of the thinset.

I don't ever recall using RedGard over Hardie.

Hi mongoct, my contractor told me he is using a barrier called aquabar made by fortifiber which is sold at HD in rolls. How do I know if this would be sufficient as a vapor barrier? is there some statistic to look up? otherwise I can purchase the redguard or kerdi, but is there a specific product you can direct me to? these companies make so many products, it gets confusing to know which is the vapor barrier and which are only good as the moisture barrier.

"How do I know if this would be sufficient as a vapor barrier? is there some statistic to look up? "

Aquabar really isn't the proper membrane for a shower or steam shower. It's a bit of a hybrid product in that it has an asphalt core with a kraft paper facing on each side, you can sort of think of it as a 3-ply product.

It's normally used as a slip sheet for hardwood floor installations. Lemme see if I can find a tech sheet on it...

Yeah, it's not a product you want him putting in your steam shower. Go to this page, click on "Data Sheet" and it'll open up a pdf. Scroll down to the end and read the "Limitations" section in the left column.

To paraphrase, the manufacturer says something along the lines of "Aquabar is not a waterproof membrane and should not be used in waterproofing assemblies or where a waterproof membrane specified...do not use in saunas, steam rooms..."

If he bought the Aquabar at HD, it's easy for him, as both RedGard and Kerdi are sold there as well.

These days you pretty much have to do what I did. Go to the manufacturer's website and read the spec sheets. A vapor barrier will have a perm rating of less than "1". If you're still not certain, find the company's tech support line and ring them up. It's an easy call to make, and all you have to ask them is if they recommend their product for use as a sole vapor barrier/membrane in a steam shower.

Some products dance around the issue. Wedi board, which is an excellent tile backer board, says that their product can be used as a tile backer in a steam room...if you use an epoxy adhesive to set the tile and then use an epoxy grout. In that instance, its the epoxy that is the vapor barrier, it has nothing to do with the Wedi Board.

So confusing? It sure can be.

Mongoct and all, thank you so much for all your help. We are going to use all Kerdi products, following the installation instructions, over the hardiboard. They will warranty the steam shower for 5 years. So thank you for helping to navigate the confusing options.

Mongoct, ditto what everyone else said. thank you so much! you are truly an asset to gardenweb. i will look for something else for the vapor/waterproofing. I think my contractor has to put in the aquabar on the floor as code, but sounds like I should have him do an additional vapor barrier over it. Redgard seems like an easier product (he has never used either of these) -- kerdi seems to require more skill (like wallpapering?) to apply.

First, "you are welcome" to all. Thanks for the kind words.

Second, "I think my contractor has to put in the aquabar on the floor as code, ...":

If he wants to put in on the bathroom floor, outside of the shower, that's fine. If he plans on using it as a waterproof or vapor membrane inside the shower on the shower floor, Again, I'll simply refer you to the "Aquabar is not a waterproof membrane and should not be used in waterproofing assemblies or where a waterproof membrane specified..." from my previous post.

Third, regarding "Redgard seems like an easier product (he has never used either of these) -- kerdi seems to require more skill (like wallpapering?) to apply.":

Yes, RedGard is easy to apply. You just "paint" it on, so to speak. But care needs to be taken to get proper mil thickness, and to avoid pinprick holes. Especially in a steam shower. And care also need to be taken regarding how to detail the RedGard-to-drain when using RedGard and what I asume will be a clamping drain.

Personally, I think Kerdi is pretty darn easy, especially due to the use of the Kerdi Drain. FWIW, the Kerdi Shower that I show in that previous link was the first time I'd ever used Kerdi.

Just one more question - what if you're using Kerdi but not the Kerdi drain? the plumber has long since installed the requisite drain....
thanks again.

"Just one more question - what if you're using Kerdi but not the Kerdi drain? the plumber has long since installed the requisite drain...."

Is there anything on the shower floor now? If it's flat subfloor and just the clamping drain set in place, the drain can be cut out and replaced with a Kerdi Drain.

And that's exactly what I'd do. It may seem like a step backward, but it's actually a huge step forward.

Other than that, it depends how far along the shower floor is in terms of being constructed. There's a drain. Is the membrane already installed over a sloped mud bed? Is there a tiling bed of mud already on the membrane?

There's not really a proper or practical way that I can think of to tie Kerdi membrane on the floor into a clamping drain. You can use the "divot method" with liquid topical membranes.

EDIT: I went back and read your previous post that ""The cement backer board is up on the walls."

In that case, with the clamping drain also already installed, you either have a "traditional" CPE or CPVC membrane already installed on a mud preslope, because that type of membrane has to be run up the walls (between the studs and the cement board) about 10 inches. So it has to be installed before the cement board goes up.

OR if there is nothing on your shower floor except for the drain, then your guy is probably planning on using a liquid topical membrane with the divot method.

I usually recommend keeping things simple. If you're using Kerdi, use Kerdi on all surfaces and a Kerdi Drain.

If you're using a topical liquid membrane, use the same membrane on all surfaces.

I'd ask your installer what materials and methods are being used. If anything sounds funny, feel free to ask again. I'll be hit and miss on the forums for the nest few days but others can answer too.

I don't know the diff between a drain and a clamping drain, and the other comments are getting too technical for me, but I can tell you that the drain threads are very specific/unusual, and the drain has weep holes. There's a copper pan, and the kerdi tech told us what exactly needs to be poured. The pour has not taken place yet.

I have seen a steam unit in a shower with a limestone slab bench seat crack the slab... Smaller travertine and limestone tiles in the same shower seem to fare okay, but the slab is much too soft to be exposed to the extreme heating and cooling in a steam shower. Be careful!

If the drain has "weep holes," then it is an FHA/PVC type drain and cannot be used with Kerdi. As Mongo pointed out, best to cut it out and use a proper Schluter/Kerdi drain. IF that is problematic, Schluter does offer an adapter drain that attaches to the lower portion of the existing drain body.