Steam Shower [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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02-23-2008, 05:13 PM
I wanted to start a new thread since I have a new perspective on my project. I'm the guy that posted "Steam Shower built by rookie" thread. We live in Denver, no exterior facing walls, and right now it's porcelain tiles over 1/2" thick hardiebacker.

I AM tearing it out after contemplating epoxy grout and siliconed seams, I just don't want to take the chance of it not being done right.

I've read LOTS of other threads (even on other forums) and it seems that the most highly recommended product is Kerdi as a vapor and moisture barrier. Funny thing though, I can't find anything on Schluter's site that blantantly says "this product is recommended as a vapor barrier for steam showers." It always talks about it being a waterproofing membrane.

Where there is still debate (even on this site) is whether or not to put it over drywall or CBU. I called the guy at and he not only recommended doing the Kerdi system over drywall and NOT CBU, but he said it was a much better way to go. Then though, I read a thread on this site that says that putting drywall in a steam shower is an absolutely bad idea and you should always use CBU?

Also, the Kerdi permeance rating wasn't yet published and that the Noble permeance is even better than Kerdi. What is the straight dope on this?

Would you guys reccomend treating the studs with anything, or should I just screw the drywall right into the studs and then just thinset the Kerdi (or Noble) right onto the drywall and call it good... then just tile?

For the benches, do I even need cement board if I am using Kerdi, or just one layer of 3/4 inch plywood will be good enough.

One more, would the Kerdi shower book help for this steam shower build? I mean, is it the same method whether it's a steam shower or a regular shower or do you install the Kerdi differently because of the steam, or use a different type of Kerdi product for steam? As far as I can tell, it's all the same stuff.

I am going to start tearing out....

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02-23-2008, 05:51 PM
Hey Fletcher, what happened to your signature?

I don't think you've ever read a pro say that drywall was a bad idea IF it was to be covered with Kerdi.

You 'll of course need to build the bench out of plywood, but you can't install Kerdi over plywood because you're using unmodified thinset. Install either CBU or drywall over the plywood first.


02-23-2008, 06:42 PM
Good "catch," Jaz. Build the bench out of block or plywood and then put drywall over it. Cover it all in Kerdi...........

02-23-2008, 10:54 PM
Drywall crumbles under weight doesn't it? I am skeptical of drywalling a bench just because drywall seems to flake/crumble at the edges. Wouldn't you guys be concerned about that? Can you picture a 13 year old kid standing up on the edge of the bench and putting all their weight on the lip of the edge and the drywall giving in to the weight? I dunno.... Also, on another site (JLC Online) guys are saying to use CB and not drywall. I guess I need it straight from Schluter's mouth.

Does it seem strange that nowhere on Schluter's website do they advertise it as a system for steam showers, rather just a "shower system"? Are we 100% sure the permeance ratings are correct for vapor?

Sorry to sound so skeptical, but tearing this out and doing it over is a big deal for me and my family, I need to know FOR SURE that Kerdi is the way to go, and not Noble, etc.

Thanks again as always. You guys are great. I am going to keep studying this until I myself am a "steam shower expert", at least good enough to advise other people so I can repay you all for the help you have given me by posting answers for other folks some day.

I am going to call Schluter as well and get ahold of a local rep and ask him all the questions...

02-23-2008, 11:48 PM
Use cement board if it'll make you feel better. (As I did in the link above). Don't forget the drywall is fully supported with plywood underneath, AND there's tile over it too.

As far as being suitable for showers, yes it is. This is from the Schluter site, albeit hard to find.

Q. Can I use Schluter-KERDI in my steam shower?

A. Yes. Schluter-KERDI has a low water vapor permeance (0.75 perms), allowing it to function both as a waterproofing membrane and vapor retarder in steam showers.

I didn't look how Noble compares, but that's easy to find out.


Brian in San Diego
02-24-2008, 07:21 AM
Jaz and others, correct me if I'm wrong...I thought if you are to use kerdi for a steam shower then the substrate needs to be CBU. I thought the drywall was for showers, CBU for steam showers.


John Bridge
02-24-2008, 08:10 AM
Use Noble if you're more comfortable with it. It's a great product. :)

Kerdi is thinner, though, and there will be less buildup in seams and corners.

If drywall makes you uncomfortable, use CBU behind the membrane. It's a perfectly fine backer for Kerdi membrane. A foam backer would be another.

Schluter does not specify anything other than drywall behind the membrane in residential applications at least. There has been talk of the heat, not the water, possibly affecting the composition of drywall over time in commercial steam rooms where the heat is constant. The likelihood of that happening in a residential setting is remote at most and probably non-existent.

If I were building a Kerdi steam shower in my home I would use drywall as the backer. I just can't add much to that. :)

The Kerdi Shower Book is a definite aid to anyone building any type of Kerdi shower. It's certainly not a know-all end-all book, but it is the only book on the market that is devoted entirely to Kerdi products and techniques.

. . . and it was written by a very suave, good-looking and more or less knowledgeable Kerdi shower builder. :D

02-24-2008, 01:23 PM
One word to keep mind...RESIDENTIAL. A close friend of mine owns a spa and health center at a local hotel. The place is open 16 hours a day and the steam shower is on for over 12. Not sure the building criteria should be the same.

- pete

02-24-2008, 04:59 PM
I have a few more things to ask, but don't feel like I need all of the answers if you aren't sure. I hope it's OK to continue to ask. I am almost 100% informed here, I've learned a lot in the past fews days thanks to you all.

I am going to talk to the local Schluter Rep. tomorrow, I think his name is "Bart Wilde", some of you might know him since you went to the "Schluterfest" last year. Great coverage on that by the way, I feel like i Know some of you!

So I will ask specifically about drywall and steam showers. I bet drywall is find since their Q&A says YES to steam and YES to drywall without clarifying whether or not the DW is for steam or showers.

Just one more thing I am wondering, and that is, can Kerdi stick to Kerdi? I mean, if I use the corner pieces I would think I would install them FIRST, before the vertical pieces, but still put "pancake batter thick" thinset over the top of the dried corner pieces at least 2 inches in so that I can then adhere the new vertical pieces to the corner pieces. The same question would apply to the Kerdi band too... would I do the vertical pieces first and then the band over them in the corner seams, or vice versa, and either way, it seems like I'd have to put thinset over the cured Kerdi, right? The website didn't talk specifically about that.

Does the sequence of installation of Kerdi matter as far as ceiling, wall, or bench first, and if so... why?

Are expansion joints of supreme importance? I just did regular 2x's for framing but I used screws generously. Do you think the heat from the steam will move the joints/walls and then start popping my tiles and grout, or because I am in a dryer climate maybe I am safe bypassing the expansion joints with moderate to low steam shower usage?

Well heck, one more.. and then I really do think I have all of my questions answered: I have a TileRedi shower pan in there and their claim to fame is that this is a pre-made pan that is guaranteed for life not to leak, etc. It has 4 inch high sidewalls and a curb. The bonding stuff they sent with it is called "Latapoxy." So now again I wonder, do I put Kerdi on top of the TileRedi pan, or do I just run the Kerdi down the walls until I meet up with the bottom of the walls? If I do Kerdi the pan, do I use thinset or do I need to use Latapoxy? This might be a question for TileRedi, but thought I would throw it out there. If I don't get an answer, then I'll call them too tomorrow.

02-24-2008, 05:10 PM
When whomever mentioned waterproofing/membrane I would be positive it was a mudman! My walls are impenetrable to small arms fire. Sort of like the current trend of safe rooms! My shower walls will allow u the opportunity to return fire. But, hey - drywalls cool (yeah right)!!!!!!! Skanks :shake: But you're :deadhorse round here. And all that material is soooooooooooooo spensive! :wtf: But, anyway. When I do use that particular method , I overlap the material and seal with a thermoplastic sealant. :idea:

02-24-2008, 08:10 PM
I'd like to hire a mudman, but wouldn't that cost a lot more than the $500 or so for the Kerdi system?

02-24-2008, 08:15 PM
Materials=no (pennies on the dollar for sand/cement/lime)
Days Labor=250+
You tile=free
No leaks=PRICELESS :nod:

02-26-2008, 07:35 AM
This is all you need to know about installing Kerdi. Note the drywall

03-09-2008, 07:51 AM
It's me again... the steam shower DYI guy who messed up his steam shower and is having it redone. The 3 man crew I hired tore out the old steam shower and Kerdi wrapped it all in one long 12 hour day. That's what you get when you hire the pros: Good work done way faster than I ever could have done.

They are doing excellent work and the Kerdi wrap was done VERY well, I have no concerns at all about leaks now or years from now. I watched them do it and learned a lot about it.

The point of this post: These guys are indicating that epoxy grout is not important in my steam shower, that normal grout sealed with an impregnating sealer is sufficient... even for steam.

What do you guys think? Do you agree? As the homeowner I could insist that they use epoxy grout, but I want to be reasonable here, and well informed of course.


03-09-2008, 08:58 AM
They are correct about the lack of "need" for epoxy grout just because it's a steam shower, Craig.

But if you, as the bill payer, want epoxy, I'm sure they will use epoxy. You, as the bill payer, will expect to pay a bigger bill, eh? :shades:

The primary selling point of the epoxies is the consistent color and ease of cleaning. They should be able to get the consistent color with a regular cementitious grout, but that's not a guarantee. A good penetrating sealer will aid in keeping the grout lines clean.

Dealer's choice. No technical requirement either way.

Sounds like you found you a good mechanic.

No reason not to post his name up here for others to see and give him proper credit. Might also suggest he visit the site; we're always looking for more good help, too. :)

My opinion; worth price charged.

03-09-2008, 09:29 AM
in a steam shower I would NOT use Dry wall..Nobles Perm rate is SEVERAL times better.(WVTR .048) But SOME moisture still passes..As long as your building it from from the studs out ,why not use a board that is not food for mold and is suitable for wet areas..For just afew more dollars why cut corners?

03-09-2008, 10:21 AM
I gotta agree with our friend, Eric. :)

03-09-2008, 09:15 PM
I double verified this with Schluter themselves: They do hold that drywall is perfectly fine in a steam shower with Kerdi properly installed. However, we (they) resue the cement board I already had there, but said that they usually use drywall for Kerdi. I know it sounds crazy! Call your local Schluter rep and discuss it with them if ya like?