Steam shower question [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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01-17-2017, 02:39 PM
Good afternoon. So i have a question for you. I have been asked to install a roll-on/paint on hydroban waterproofing on the walls/ceiling for a steam shower of durrock cement board. Will this work? Even if i apply 2-3 complete coats of the hydroban i am just not sure if this is correct process. My head was telling me to use a product like a Schluter kerdi system. Any help would be appreciated. Thank you.

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01-17-2017, 04:55 PM
Any painted on waterproofing system calls for 2 coats (not 1, not 3 or more). You need to read the spec for the material regarding its perm rating and pay VERY careful attention to the installation instructions for it to work along with excellent craftsmanship and execution - IMHO, it's a little easier to obtain the required perm rating with a sheet, but, at least with some liquids, it is possible, at least for a residential rating. There are different requirements for commercial, constant use steam showers verses occasional use, residential ones - is this residential or commercial?

The product you select will depend on the application and the required perm rating.

01-17-2017, 07:44 PM
Thank you jadnashua. This is a new home residential construction application. I think i am going to pursue the Schluter system. I have not installed one of these before. I have read the installations before but would like some advice. Can anyone here help me out as for as the process goes?

Houston Remodeler
01-17-2017, 07:48 PM

Call your area Rep. This is what they do. There are free hands on seminars as well. Watch as many Schluter videos as you can.

01-17-2017, 07:50 PM
Doug, Ditra is not a material you would use in a shower, steam or otherwise. Perhaps you are thinking of using Schluter's Kerdi membrane?

If so, I would recommend you visit the Kerdi website ( and download the Installation Handbook for the product and become very familiar with it before you go any further. Steam showers are not something you want to undertake casually.

Will this be a residential or commercial use steam shower?

01-17-2017, 07:56 PM
Thank you guys.
@CX yes, i had my terminology incorrect. I meant the Schluter Kerdi Membrane.
This a new construction residential application.
I am looking into the Kerdi web-site right now.

01-17-2017, 09:13 PM
@CX. Thank you for the link to the Schluter Kerdi site. Very helpful. Now the install seems pretty straight forward. My question would be what kind of prep work should be done behind the cement board/green board prior to the installation of the kerdi membrane? I am excited to install this.

01-17-2017, 09:24 PM
Keep in mind that Kerdi does not qualify for use in a "continuous use" steam shower, Doug. I would have no objection to using it in a residential steam shower, but I would want a CBU as the backing material.

You'll want substantial insulation in the shower walls and ceiling (and under floor if applicable) and you must have a ceiling sloped a minimum of 2" per foot, movement accommodation joints in all changes of plane, among other requirements that are different from a traditional shower. I would strongly recommend you get a copy of the current TCNA Handbook and look at the recommendations found there.

Again, not nearly as simple as building a shower.

My opinion; worth price charged.

01-17-2017, 09:31 PM
Thanks CX!
Yes i caught that from the Kerdi site too. It is a residential shower. Not going to be used as a steam shower regularly. But it has the capability to be used as one. As for your comment about CBU, you mean cement board correct? Just want to get my facts right. The ceiling is no issue for slope. As a matter of fact it is a cathedral ceiling in the bathroom so it has an extreme amount of pitch. As for insulation, one wall is located on the exterior side of the home. So obviously there is insulation. The question is here, should there be visqueen or some sort of vapor barrier placed over the insulation prior to the cement board install? Thank you again.

01-17-2017, 09:48 PM
CBU=Cementitious Backer Unit.

I would not want any vapor barrier material on the other side of my CBU wallboard. In your part of the country I would actually prefer to build another 2x4 wall against that outside wall for additional insulation, but that's entirely up to you. As long as you have at least 2x6 wall construction, well insulated, you may do fine. More is better when building a steam shower.

My opinion; worth price charged.

01-17-2017, 11:26 PM
There are two varieties of Kerdi, the 'normal' stuff, and KerdiDS which is thicker. To meet the commercial rating, you need the thicker stuff, but Kerdi should work fine for an occasional use residential steam shower. Both are waterproof, but KerdiDS has a lower perm rating than Kerdi.

The biggest hassle people have with installing any sheet membrane over CBU is ignoring the requirement to dampen the wall surface. Some CBU's are worse than others, but they all will suck a significant amount of moisture out of the thinset prior to you being able to install the membrane, and that makes embedding the fleece really difficult. On none of the sheet membranes, does the thinset actually stick like a bonds because it needs to flow around the fleece, and then, when it cures, it locks things in place.

01-18-2017, 02:56 AM
Here are the perm ratings for some products that you may consider using for your steam shower:

USG Durock Shower System Waterproofing Membrane 12 mil perm rating <0.075

Schluter Kerdi-DS 20 mil perm rating .18

And for your paint on membrane
Custom Buildings Redgard Liquid 30 mil dry film perm rating .36

While it may seem easier to use the paint on product, in reality, it probably takes more skill and attention to detail to wind up with a minimum 30 mil dry film over the entire surface of the shower than it would be to use one of the other two products.

01-18-2017, 09:51 AM
Thank you jadnashua & Actuary. I have the installation manuals and the material check list in hand for the kerdi schluter shower systems. I need to get specifics from my builder and the client: Type of tile to be used, body spray count, control location, steam generator location, drain desire orientation, niche locations. There is quite a bit of planning involved. Now the next question i have is: Is there a particular tile i should direct the client towards or away from? Meaning porcelain vs natural stone? Will either have an issue adhering to the membrane with the non-modified thinset as the manual calls out?

01-18-2017, 11:16 AM
I will only add that you should NOT use "greenboard." Regular drywall, please.:yeah:

01-18-2017, 11:20 AM
Okay. To recap, the current conditions in the new construction home are as follows:
Master bathroom Steam Shower: 1/2" Durrock cement board
Boy's bathroom shower: 1/2" green board drywall.

So i will discuss the drywall in the boy's bath and ask it to be removed by the builder. Will the 1/2" Durrock cement board work for both areas then?

01-18-2017, 11:40 AM
Yes, Durock cement board works for both showers.

Here's a link to the Schluter installation manual

Page 6 - Shower Assembly
Page 16 - Steam room assembly
Page 18 - Bathtub surround assembly

01-18-2017, 01:53 PM
Thank you Actuary. I have that entire pack printed off. But i can now flag those pgs. and read up. I plan on having the green board removed in the boy's tub surround and install 1/2" cement board. Then of course tape the seams with fiber-mesh followed up with a flat blade troweling of thinset. Then the kerdi install.

01-18-2017, 02:01 PM
I could be mistaken, but if your installing kerdi over cbu on a tub surround there's no need to mesh tape the seams. Applying kerdi will take care of the seams and corners.

01-18-2017, 03:40 PM
While the cbu is good for the steam shower and is an accepted substrate for a shower, the normal shower will work just fine with regular drywall if you're going to use Kerdi over it (and, no taping or prefilling of the seams). If you have a tapered joint in the area, you might want to prefill that with thinset to level it out, but the Kerdi over the top will be much more effective than a reinforcement tape.

It is CRITICAL to wipe the walls down with a (very) wet sponge prior to spreading the thinset to both remove any dust and to keep the walls from sucking too much moisture out of the thinset. Some people go to the point of using a sprayer to wet the walls. They're only too wet if there's liquid water on the surface...very damp is ideal. The difference in how easy it is to then embed the membrane is like day and night when the thinset is mixed properly per the instructions. Overwatering thinset risks other issues - material separation, weaker, slump, etc. Not having the wall suck moisture out keeps things consistent.

01-19-2017, 12:15 PM
Thank you jadnashua & rmckee84. Yes, i am aware that the walls want to be wet-down as the instructions call out. I will not worry about mesh tapping the seams and thinset unless as you mentioned the depression is noticeable. Do you have input over why green board drywall might not be a good application vs standard drywall? I already plan on removing the green board and installing the cement board...just wondering why.

01-19-2017, 01:01 PM
Green board has a waxy coating that can make it difficult to adhere to.

01-19-2017, 01:02 PM
Fair enough. I understand. It's coming down. Durrock going up!

01-19-2017, 04:05 PM
The sheet coating typical greenboard is not as strong as the paper used on drywall, and especially on a ceiling, it will tend to deform under its own weight unless you frame and support it at shorter spans than drywall will survive.

If you're not familiar with it, take any sheet of paper, even newspaper. Tear it vertically along its long axis, then tear it horizontally along that axis. In one case it will tear easily and in a fairly straight line, and in the other, it will make a ragged, irregular tear. The paper fibers have grain in them. If you buy copier paper and have trouble with it jamming more than normal, you may have bought paper that has the grain running the wrong way. It's sold as both 'long' and 'short' grain, with that grain aligned with the long or short length of the paper. Typically, you want the grain to run in the direction the paper is fed (side or end), and when installing drywall, across the supports, not aligned with them, just like when installing plywood.

WHat most people call greenboard has not been allowed in a shower for ages.

01-20-2017, 07:44 AM
Thank you jadnashua. I am familiar with what you are explaining. Cement board it is. Should i inform the client of any particular types of tile that would be suitable for a steam shower vs tile material that would not be appropriate? I could easily just let the tile salesman sell them whatever they like, but i am the one installing, it's my name on it, all he does is sell. I want to cover my rear and make sure we are doing this correctly.

01-20-2017, 11:14 AM
Avoid glass if possible especially large format glass.

01-20-2017, 11:48 AM
Thank you rmckee84. No it. I was curious if a natural stone travertine or tumbled marble would work. I know they are more porous. Not sure if that would be good for a steam shower or not.

01-20-2017, 12:31 PM
I have yet to do a steamer, I just know that glass can be an issue just from seeing the problems it has caused for others. I would think porcelain would be your best choice, but whatever is picked I would call the manufacter and check with them before I installed.

01-20-2017, 02:59 PM
While I do not have practical experience with a porous stone in a steamer...I've seen what the granite in my personal shower does, and it experiences a change in color after being wetted (Kashmir white). As a result, I ended up using an enhancing sealer to make it always look wet to even things out. Note, some marble and travertine aren't even recommended for a plain shower, so I would think a steamer would be even worse. Trying to get the absorption rate on a particular tile is sometimes tough - they can vary radically.

01-20-2017, 06:25 PM
Doug a lot of great advice here, I don't have much to add. I would not use travertine or marble in a steamer it will more than likely etch the surface and be one big pita. I just did one couple months back and we had vertical glass liners, difference is the size. We have seen installations where the glass has cracked but we aren't speaking of glass in this format but glass tiles because of all the movement and contraction going on from the steam.

One I did was porcelain tiles with glass elements though we did use solid material for the big shelf. Used the Hyrdro Ban sheet membrane. All the tile was spec'd out for this project and the guy who was going to do it got deployed. They did hang the cbu and the guy I spoke with said they were going to use Hydro Ban liquid but after speaking with my Laticrete Rep. the only way you could use the liquid is if you have poly behind the cbu draped over a liner in the pan. The Hydro Ban liquid will waterproof the walls but not vapor proof it, the vapor will get through and this is why you need the poly behind the cbu.

We did have a pan liner but there was nothing behind the cbu so I opted to go with the sheet membrane. Similar to kerdi.

01-21-2017, 09:10 PM
Good evening. Thank you for all the input. I appreciate the kind words and advise. I will be having the builder double check with their tile supplier to make sure the material is spec'ed out for a steam shower.
jondon~ Thank you for sharing the project pictures. The work looks great. I agree, the porcelain in my eyes would probably be the tile of choice. We will see.