which waterproofing system for new shower?

Discussion in 'Shower & Bathtub Forum & Blog' started by ratherbefishing, Dec 10, 2011.

  1. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,273
    Location:
    New England
    What you seem to be missing is that independent testing agencies have tested and approved Kerdi for use over drywall in a shower. The IPC being one of them. TCNA another.

    Kerdi is NOT approved for installation over wood, never was, never will be, so, if you want a curb out of wood, you sheath it in drywall or one of the other acceptable backing materials as listed in the testing spec and approval, or, build it out of something else.

    Directly from the ICC Evaluation Service Report ESR-2467, Section 2.0, it lists the specific approvals. I could not cut this and paste, so I'm retying it:
    "KERDI is also used as a shower lining, as required in IRC Section P2709.2 and IPC Section 417.5.2 over concrete, mortar, tile backerboard, expanded polystyrene foam board, prefabricated polystyrene shower trays, curb and ramps, gypsum board and masonry substrates."

    In section 4.0 INSTALLATION, it says the following:

    " Installation of Schluter (tm) - KERDI, Schluter (tm) - DITRA and Schluter (tm) - DITRA XL membranes and accessories must comply with this report and the manufactuer's published installation instructions."

    The manufacturer's instructions show and list the same backer materials as above from Section 2.0. The TCNA guideline that also was tested and approved was referenced earlier and is listed explicity as an approved method. Now, my copy of the spec is a little older, but there have not been changes in that approval. It clearly shows gypsum board (aka drywall) as the backer in the construction detail as an approved shower construction method.

    Both Kerdi seams and Kerdiboard edges MUST be sealed with the specified overlap of seaming material, either Kerdi, Kerdiband, or KerdiFix, otherwise, it is not a waterproof ASSEMBLY. You stick a piece of cbu in a waterbath, and it will wick water just as easily as Kerdi until it is either sealed on the surface or otherwise installed per an approved method. Just setting it in water has nothing to do with whether it is waterproof when installed properly.

    The approval page from the State of Massachusetts http://license.reg.state.ma.us/pubL...P.&model=&product=&description=kerdi&psize=50
    Last edited: Dec 14, 2011
  2. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

    Messages:
    4,724
    Location:
    North Vancouver, BC
    Schluter's requirements for Gypsum Backer Boards - do they include corner beads?

    post(s) deleted by John Whipple
    Last edited: Mar 17, 2014
  3. mtcummins

    mtcummins In the Trades

    Messages:
    380
    Location:
    Pittsburgh PA
    But what isn't grey is the fact that you've been spouting bull crap all this time. That's pretty black and white.

    What do you use when doing cbu? Just board? do you fill the seams? use mesh? cover screw holes? corners? clean the surface? Pretty grey area JW.

    I don't finish drywall when using it behind waterproofing. I'll fill the voids with thinset if anything. When I'm feeling particularly fussy, I'll plan it out so that the kerdi overlap falls into the seam between boards, so that there's no build-up from the overlapping. But that doesn't work out as often with drywall as with cbu, as the widths don't line up as neatly.
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,273
    Location:
    New England
    I know I read it somewhere about prepping the drywall before installation of Kerdi. You don't need drywall mud or mesh tape...the Kerdi is far stronger than the tape anyway. If your taper portion of the drywall is to be covered with Kerdi, you can either fill it with thinset and immediately install the Kerdi, or fill it flush, let it cure a bit, then install the Kerdi on the now flat plane as it it wasn't there. In some orientations, the taper will help avoid the small buildup in the changes of plane - far easier than with the much thicker membranes.
  5. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

    Messages:
    4,724
    Location:
    North Vancouver, BC
    Does Drywall (Gypsum) have any place in a shower renovation?

    post(s) deleted by John Whipple
    Last edited: Mar 17, 2014
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,273
    Location:
    New England
    Again, John, you're missing the point. ALL seams must be covered either with KerdiFix, or the proper overlap of Kerdi or Kerdiband. If you do this with a modified thinset, the laytex component will allow wicking, whereas the proper consistency of a good dryset, where the excess is squeezed out while embedding the membrane will prevent wicking, typically less than 1/4", and way less than the specified 2" minimum overlap. Since the layer of unmodified thinset is quite thin, it won't wick much in any reasonable timeframe, maintaining the waterproof properties of the SYSTEM. ANY other testing or procedure will potentially allow moisture to seep into the edge and affect the backing material. Do not use drywall mud, at least the non-setting type, underneath Kerdi. The moisture from the thinset can soften it. Keep in mind also that like any mortar based product, it doesn't set immediately. The next day, you could likely easily peel the sheet off the wall. But, try that after a week, or the specified 28-days for stated strength of any mortar, and you'd tear the fleece off the membrane, if you could get it off. After a short time, the grip is still quite good, and sufficient to set your tile, it just gets stronger after time. The fleece is, I think, required to hold 50psi in shear to pass the tests, and when tested showed 75psi. These specs and test material are in the handbook. The Kerdi membrane covering the whole seam in drywall is MUCH stronger than the tape, and is all that is required to tie the two sheets together. You do not want or need drywall corners if it is going to be covered with tile. If you did use them, you'd need to affix the Kerdi with Kerdifix, as thinset is not approved to hold Kerdi to metal.

    Anyone can devise a test and prove anything can fail. But, Kerdi, when properly installed AS A SYSTEM, creates a waterproof shower. Properly seal your seams, and you won't get moisture beyond approximately 1/4" into the seam which still has about 800% backup before it could create a problem.

    And, consider that in a properly completed shower, there is VERY little to no constant liquid water underneath the wear surface, the tile. It won't accumulate if your slopes are proper (and would still be waterproof if it didn't). So, since the migration and waterproofing is done with standing water in a flood test, as long as you don't penetrate the seams, once tile is installed, you're golden. Like anything, quality of craftsmanship and proper adherance to the manufacturer's instructions yields a successful result. Miss a step, and it can fail. But, the golden, simple rule with Kerdi (and any sheet membrane) is, verify proper embedding of the fleece to the backer, and make proper seams.

    Schluter has 35-years of experience with this product and the technique to install it properly is described in their manual. The approval agencies all specify that it must be installed per the installation manual. Do it that way, don't try to improvise, and it works. The system is quite flexible. If you can install wallpaper, you have a high probability of succes, assuming you can read and follow instructions. As good as (and in my opinion a better chance) of any other system out there in a successful install.

    I'm at my sister's now, trying to fix some supposedly pro tile installs...rotten subflooring, broken tile, nasty. Not all pros are that. They broke a lot of rules in this house and she's now paying for it. One would hope in a $600K house that wouldn't be the case. Do it right, and it works. Do it wrong, and you may be lucky, but it will probably fail...true for anything. 35+ years of field experience in the USA says Kerdi works.
  7. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

    Messages:
    4,724
    Location:
    North Vancouver, BC
    post(s) deleted by John Whipple
    Last edited: Mar 17, 2014
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,273
    Location:
    New England
    The TCNA procedure I listed previously clearly shows drywall in the wall stackup of a shower build as an approved, tested procedure. That a clerk didn't know it has nothing to do with it. All you have to do is read the manual, view the construction diagram, and it is readily apparant. I don't have my copy with me at the moment, and scanning and posting a copywrited image is not allowed. But, if you don't already have a copy of the TCNA handbook, get one. Then, all of your issues go away - assuming you believe the testing agency and Schluter's 35-years of using it in the field.

    If you use a modified thinset to make the seams, or you leave an excessive amount of thinset, or you allow water to enter from an unprotected edge, moisture will wick into the substrate. this will wet the material. In these cases, the material was not installed properly. It's pretty easy once you understand the principles and adhere to the instructions.

    The whole goal of a sheet membrane waterproofing material is to completely waterproof what's underneath it. Done properly, as long as the material underneath is solid and thinset will stick to it adequately, is stable when dry, then it works. Drywall is one of the approved backing materials as tested and approved by the TCNA and IPC, regardless of what the clerk said. It's in their manual in plain text and a diagram.

    If you don't want to believe me, buy or borrow a copy and see for yourself. They make the documentation so you don't have to rely on what someone thinks, only what has been proven to work and documented, and approved for use for that application. Like anything, if you don't follow the instructions, your results may differ.

    Feel free to use a different backing material if it makes you feel better. Don't say the years of experience and the testing agencies (IPC and TCNA) that have validated it are wrong. I'd have no problem if you said I don't trust drywall, and would only use cbu but the testing agencies say it works, I just don't trust them. That's sort of like saying you don't trust the UL or CSA (?) electrical safety test, or the car crash test results, or that smoking isn't good for you. You can choose to ignore that, but you'd be wrong.

    There is no reason to prefill the joints on drywall with drywall mud prior to installing Kerdi. So, that whole issue goes away. If you did, then just like anything, you need to make the surface compatible. It's not the Kerdi, it's the thinset moisture that's an issue with mud or anything that can re-emulsify, and you wouldn't tile over cbu with drywall mud on it, nor should you install Kerdi. Think of Kerdi as a huge tile that is continuous and waterproof. Once that is installed properly, you can put your decorative wear surface on top. Done right, it's totally waterproof. Like anything, miss a step, and you can have problems. On a conventional shower, there are numerous ways to mess up: blocked weep holes, poor seaming, failure to use corner pieces on the curb, nailing into the curb or low in the liner when installing the walls, lousy joint at the drain, a missed corner cut not covered or repaired. On anything, good workmanship and following the prescribed instructions must be done. Personally, I think it's easier with Kerdi than many other systems, but that's my choice. You have yours...doesn't make it wrong or unacceptable except when you say it doesn't work.

    A good example of what it can do was mentioned previously where after regular use as a drink cooler box with ice and water in it, the box was still dry and intact after many months at the TCNA school. They replace it periodically because like any paper product, when you flex it enough, it gets floppy. It wasn't from getting wet, as you could look at the thing at the end of the day and it was entirely dry on the outside. The Kerdi was installed with the proper thinset and technique. Do it right, do it once, sleep well.

    A properly built shower, except during the flood test, should never have standing water in it. The membrane is waterproof and the seams will be too, when done right. It's not really that hard.
    Last edited: Dec 16, 2011
  9. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

    Messages:
    4,724
    Location:
    North Vancouver, BC
    post(s) deleted by John Whipple
    Last edited: Mar 17, 2014
  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,273
    Location:
    New England
    As I said, regardless of what people say, the testing agencies: TCNA and IPC have both tested Kerdi over gypsum board (aka drywall) and approved it. It's right in the TCNA manual, clearly shows drywall with Kerdi over it in the buildup diagram. The IPC test report says the same thing: ESR-2467 Kerdi-Ditra IPC certification, reissued 1 August 2011, only a few months ago. It was issued previously, I saw a copy in 2005, and there may have been one earlier as they have a limited life (the current one is subject to renewal in two years - the testing methods and requirements may change, so they don't want to issue one good forever).

    Here's a link to the latest certification on Kerdi and Ditra http://www.icc-es.org/reports/pdf_files/ICC-ES/ESR-2467.pdf. Note in section 2.0 where it talks about Kerdi for use in a shower and the acceptable backer materials.
    Last edited: Dec 16, 2011
  11. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

    Messages:
    4,724
    Location:
    North Vancouver, BC
    post(s) deleted by John Whipple
    Last edited: Mar 17, 2014
  12. mtcummins

    mtcummins In the Trades

    Messages:
    380
    Location:
    Pittsburgh PA
    Am I missing something? Is not everything in your last post supporting what Jim and I have been saying (other than the curb thing)?

    As for curbs, I agree with John and disagree with Jim and Schluter on that point actually. I would never use drywall on a curb if I were to custom build one. I usually just use Schluter's curb, but if I built one, I would use Hardi. It just gets too much foot traffic for drywall... I wouldn't use drywall as a floor substrate, so I wouldn't use it for a curb, which is a floor substrate.

    However, everything Dale said is confirming what Jim and I have been saying. Yes, you can use drywall in a kerdi shower. In fact, Chris even said its the recommended substrate. Dale said: "They may indicate for use only in dry areas which once the Kerdi is applied the drywall will never see a drop of water." This sounds remarkably like what Jim and I have been saying for weeks...

    I personally never said anything about using regular drywall. I only use MR board in a bathroom, I wouldn't bother to change from MR to regular for the shower, I do it all in MR. I don't think Schluter requires MR in general, their pictures certainly show regular. However, I'd definitely use MR. Also, their pictures and instructions don't show any priming. I think that would only be required if you mudded the drywall, which I don't do.

    Once again, Jim and even your reps have cited those organizations approving drywall in a shower. Why you refuse to listen to that confuses me.

    Your poll means nothing. If I came across that poll outside the context of a Kerdi build, I'd vote "No" as well. Why don't you post a poll asking if it is ok to use drywall in a properly installed shower, per Kerdi's recommendations, and approvals given by all your organizations? I bet you get a different response.
  13. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,273
    Location:
    New England
    The key point in the response you got was "the drywall would not see a spot of water". Therefore, it is in a dry area, not wet, which is the reason the testing agencies part of TCNA and IPC both say it's okay. The State of MA and others agree, and allow it. The inspector in NY where I did a shower for my mother accepted it.

    If the tile for the curb was a reasonable size, it would be fine over drywall firmly attached as a sheath to the 2x4. The bond is tenacious, and the Kerdi membrane, thinset, and tile make a really strong surface...probably stronger than the foam kerbs, so I don't see a problem there. Use whatever you prefer that lets you sleep well as long as it is one of the approved backers.

    Re the drywall mud...I would NOT mud the seams or nail/screws prior to installing Kerdi, therefore, I wouldn't have a problem. I wouldn't worry about it much if it was a small area and there was untouched backer material around that area as even if it did re-emulsify, it would eventually dry out since no NEW water would get there from the use of the shower.

    Opinions are common, knowledge of the product and proper installation and application apparently is sparse from people that either won't or can't read the test results and the manufacturer that has been fielding the product for over 35-years.
  14. BobL43

    BobL43 DIY Senior Member

    Messages:
    1,794
    Location:
    Long Island, NY
    As a DIYer, and I respect both of you, I'd sooner take advice on how to build a great waterproof shower that will last, from a guy that has spent his life doing this work than someone who has not done many, no matter how much theory and data sheets he's memorized. John makes a lot of sense to me in how he works things out and gets them done. If I asked advice from a guy who may have done 6 showers total, but knows a lot of mfrs info, I'm not so sure I'd take the advice of the less experienced guy. yes, there are lots of old timers that are so full of themselves that nobody else could be right, but I don't feel John fits that category . I'd take his advice here from listening to these 50 something posts. And Jim, your advice is great also, but I have chosen here
  15. mtcummins

    mtcummins In the Trades

    Messages:
    380
    Location:
    Pittsburgh PA
    I don't want to speak for Jim, but I doubt he would have any problem with using CBU under Kerdi. I think that it is fine as well. We're not saying John's method is wrong. It is interesting to note that the manufacturer specs both as acceptable substrates, but that Drywall tends to be the one they actually use in all their literature. And they've been doing all the studies, tests, etc for many, many years. What both Jim and I are arguing with is John's blind hatred of Schluter and his making up "facts" that don't exist in reality to support his ideas. I certainly won't tell you not to use CBU under Kerdi if that makes you feel all warm and fuzzy. I will tell you that both that and drywall are equally acceptable and approved methods.

    I will also tell you that it is harder to put Kerdi on CBU than MR drywall as a DIYer... it gives you less working time with the thinset, as it sucks the moisture out of it faster.

    But, either is fine. The fact is, if you build a WATERPROOF shower, which is the goal here, it doesn't matter either way. You could build it on top of cardboard, if it was rigid enough, and have the same waterproof, perfectly functioning shower (but of course this wouldn't be approved by Schluter or code). If you choose to not use drywall b/c it makes you uncomfortable, that is fine. If you choose to make stuff up, ignore the evidence presented to you, and essentially spread lies based on no facts to people trying to make an educated decision, I have a problem with that. If John would just admit that he's been wrong on all of this drywall being allowed in a shower stuff, and instead say that while it is permissible, he doesn't think it is best practice, I'd have no big problem.
  16. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    http://www.usg.com/durock-cement-board.html

    I use this on roofs and bath and showers. But for me at home, in a shower I paper it, wire lath it and stucco it before tile or granite.

    And the best damn shower pan is TORCH DOWN ROOFING. Think outside the marketers box.

    As for all the association titles after your name, "I would never belong to a club that would have me as a member".
  17. BobL43

    BobL43 DIY Senior Member

    Messages:
    1,794
    Location:
    Long Island, NY
    I tore out 2 sheetrocked showers years ago, that my builder did when the house was built. it was not a pretty sight. The good thing: the sheetrocked pulled off by hand REAL easy. Of course back then there were no waterproofing systems, other than what a craftsman had (not many did, I guess). The 2 I built to replace those both have Durock or hardibacker with 6 mil poly between the cement board and the studs. 22 years so far, still like new.
    Third bathroom has no shower, just a clawfoot tub with a hand shower to use while bathing. This one is still my current project. I don't get the impression that John'm main point is to say bad things about Schluter, but to point out other, maybe better options. Having great stuff to work with over sheetrock maybe fantastic, but if you get a bunch of handymen building showers with sheetrock and not applying all that great waterproofing system stuff exactly as specified carefully, the sheetrock will get wet, mold, fall apart long before a poorly crafted cement backer board one will. Both will be no good from the beginning, but one will last far longer. I like to at least try to use the good stuff, and give it my best work, and follow advice.

    We all have our own opinions of everything.

    I appreciate All the great advice the pros give here, but ultimately, it is "Internet" advice and my work not personally supervised by a professional crew. So far, I've done very well from what I gained here at Terry's, and from the JB tiling forum. Both are really great sites; perhaps Terry's is the very best (it is).
  18. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,273
    Location:
    New England
    I wouldn't put drywall in a shower that wasn't used in a an approved, tested, proven methodology. The main reason drywall is not generally accepted in a shower is exactly the reason BobL43 said, IF it gets wet, and if it has nothing properly applied in a shower it WILL, it will fall apart. The science in a proper surface applied membrane is not new, it's been used in Europe longer than here, but it's been in use since 1975 in the USA - I don't call that new-fangled at all.

    Bottom line, IF installed properly, the drywall is totally encased in a waterproof assembly, therefore it is as safe and strong as the walls in 98% of the houses built in the USA (the rest may have stucco or plaster - my guess, not from a study). Is your waterproof camera case going to protect your fragile camera? Yes, if it is made well and closed properly. Will Kerdi waterproof a drywall sheathed shower, yes. Do you HAVE to use drywall, absolutely not. Can you and MAY you, certainly. It is absolutely easier and less expensive to use drywall with its larger (some cbu is available in larger sheets, but god they're heavy and unweildy), less expensive sheets, and has been proven to work. A car will run with premium even if it was designed to run on regular. I prefer the easier, less expensive product and feel if it is waterproof (workmanship dependent, not product), why not.
  19. BobL43

    BobL43 DIY Senior Member

    Messages:
    1,794
    Location:
    Long Island, NY
    Actually, the bottom line IS craftsmanship. The waterprrof camera case, if it leaked a little bit, you'd see it and wipe it dry, hopefully before anty of the water touched or affected the camera. When water leaks behind a poorly applied membrane, you normally do not realize it soon enough, and that's already too late. Great craftsmanship and using quality materials go well together in doing a good looking, lasting job. There is a lot less work pride here than in Europe, still, even with the economic problems there. In general, all residential construction I've seen in Europe is far superior than what I live with here.
  20. Liquid roller-on paint-on is a good option for you.

    There are a lot of internet posts loving Kurdi, Kirdee and Kerdi. Go figure. In real world there are many other membranes. Go figure.

    I'm eager to know what swayed you after first leaning towards... K.
Similar Threads: waterproofing system
Forum Title Date
Shower & Bathtub Forum & Blog linear drains and waterproofing systems: paranoia? mix and match? overkill? K.I.S.S.? Mar 4, 2014
Shower & Bathtub Forum & Blog Tub Surround Waterproofing Nov 17, 2014
Shower & Bathtub Forum & Blog Maximum time after waterproofing application Oct 18, 2014
Shower & Bathtub Forum & Blog How to test if your waterproofing material has frozen Oct 17, 2014
Shower & Bathtub Forum & Blog Shipping Shower Waterproofing in cold weather: How to protect from freezing Oct 17, 2014

Share This Page