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Thread: which waterproofing system for new shower?

  1. #16
    In the Trades mtcummins's Avatar
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    Quote Originally Posted by johnfrwhipple View Post
    Kerdi is a recommended method of waterproofing.

    Drywall is not permitted in wet zones. You might apply Kerdi over the backsplash near your sink or behind your stove but not in your shower.

    In Europe Kerdi DS is used for primary wet zones (showers) and steam applications. Kerdi is used elsewhere.

    Many liquid membranes also list drywall as an acceptable substrate but you would be equally outside of industry standards if used in a shower.

    Best thing to do is to phone the TTMAC or purchase their specification guide. Drywall is listed only in non-wet zones.

    This is really just common sense and Jim you site the proper rules when you choose. I would imagine you have a specification guide handy. Why not open it up?

    JW
    Question... why would it matter? Lets for a minute leave Kerdi and all of its "problems" out of the picture. And lets have an answer that isn't just about "approved uses," but an actual rational thinking answer.

    If your showers are so perfectly waterproof, who gives a crap if there's drywall behind it? It's only function is to provide a stable surface to attach the waterproofing to. Drywall is an acceptable substrate for backsplashes and other tile applications, so reason would state that it would be a sufficient substrate for a shower, if it was water tight. I thought your waterproofing was perfect, so the drywall behind a waterproof shower would actually be the best place to install it, as everywhere else, its exposed to a higher level of moisture and has a higher chance of becoming a mold problem.

    That said, I'm not advocating it as a substrate behind anything that it is not specified as acceptable by the manufacturer. Kerdi specifies it as an acceptable backing. It is not acceptable to use as a tile backer w/o waterproofing in a shower, which would be a "wet zone"... can't tell you how many times I've seen that... "Ceramic tile is waterproof, right?"

  2. #17
    Retired Defense Industry Engineer jadnashua's Avatar
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    Re things like glass tile. The Kerdi instructions say to call the tile manufacturer AND Schluter to come up with a suitable workaround, if it is possible. Since the requirements can be quite stringent, and you want a warranty from both the tile and the membrane user, that collaberation is required. Chances are, you can get a suitable, warranteed install, but you need to ask. Since the exact solution may vary, they require the collaberation consulation before approval. Just like you may need approval from your local building inspector if you want to do something outside the norm. If that's too much trouble, use a different product.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #18
    ACO Shower Drain Sales johnfrwhipple's Avatar
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    Default Who cares if there is drywall in the shower?

    post(s) deleted by John Whipple
    Last edited by johnfrwhipple; 03-17-2014 at 04:33 AM.


    jfrwhipple@gmail.com - www-no-curb.com - 604 506 6792

    Always get construction advice double checked by your local city hall. Flood Test Every Shower - Every Time.

  4. #19
    ACO Shower Drain Sales johnfrwhipple's Avatar
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    post(s) deleted by John Whipple
    Last edited by johnfrwhipple; 03-17-2014 at 04:33 AM.


    jfrwhipple@gmail.com - www-no-curb.com - 604 506 6792

    Always get construction advice double checked by your local city hall. Flood Test Every Shower - Every Time.

  5. #20
    In the Trades mtcummins's Avatar
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    I love how much confidence you have in your perfect waterproofing. Properly waterproofed drywall behind a shower wall will NEVER grow mold. The MR gyp board that you put next to the shower is 10 times as likely to mold. Simple as that.

    Don't install waterproofing on drywall that the manufacturer doesn't allow.

    Your code reference is for Tile on Gyp board, thinset method. Not tile on gyp board, waterproofing then thinset method. Clearly its a dumb-ass idea to put up drywall and then tile in a shower. I tear those out from time to time, especially in tub surrounds. That is a different installation.

    Turns out OSB is not an acceptable roofing surface, unless you put a proper waterproof roof over top of it. Hmm... odd how that works, eh?

    If you don't want to use it, put in CMU, form a mold and pour a monolithic slab of concrete and use a pool liner before waterproofing, whatever makes you happy. Kerdi over drywall is accepted in the US, maybe Canada is different.

  6. #21
    ACO Shower Drain Sales johnfrwhipple's Avatar
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    post(s) deleted by John Whipple
    Last edited by johnfrwhipple; 03-17-2014 at 04:33 AM.


    jfrwhipple@gmail.com - www-no-curb.com - 604 506 6792

    Always get construction advice double checked by your local city hall. Flood Test Every Shower - Every Time.

  7. #22
    ACO Shower Drain Sales johnfrwhipple's Avatar
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    post(s) deleted by John Whipple
    Last edited by johnfrwhipple; 03-17-2014 at 04:33 AM.


    jfrwhipple@gmail.com - www-no-curb.com - 604 506 6792

    Always get construction advice double checked by your local city hall. Flood Test Every Shower - Every Time.

  8. #23
    In the Trades mtcummins's Avatar
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    You've sited many places that very obviously state not to use gyp board as a tile backer in a shower. Good for you. You've not cited anything about the substrate of a completely waterproofed area. There is a difference.

    Show me code that says you can't put kerdi on drywall.

    More than that, tell me WHY a perfectly waterproof system is ever going to mold the drywall behind it. It won't happen, unless you have a leak in the wall, in which case you're pretty much screwed either way. The walls surrounding a shower or tub are far more susceptible to water damage/mold. You don't seem to have any actual answer, just some vague references to code that does not specifically state what you are claiming.

  9. #24
    Retired Defense Industry Engineer jadnashua's Avatar
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    Refer to TCNA installation instruction B421.07, ANSI 118.10, and IPC as described in the test report linked http://www.johnbridge.com/images/mik...20ESR-2467.pdf

    Additionally, Kerdi, installed per the manufacturer's instructions, is approved by state building codes notorious for their unique take on things in Massachusetts, Michigan, and Kentucky for places that may not adhere to the IPC, when building a shower. The TCNA 421.07 allows drywall (gypsum board).

    Now, if your local codes modify these, then you must adhere to those. Just like Canada allows 1.5" drains for showers and the USA requires 2", each jurisdiction can dictate what you should use, but the test results show that, properly applied over a backing material, Kerdi is waterproof and is a decent vapor barrier. If you were in a commercial situation and required greater vapor retardation than the 0.75perm rating on Kerdi, then you'd want to install it over something else, but this is more than sufficient for any typical home use and many light commercial uses. Since it is waterPROOF, the backer material is not wet.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  10. #25
    DIY Member mcu's Avatar
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    Quote Originally Posted by mtcummins View Post
    If you're using the Schluter products (Kerdi), you could get a 48x48 Schluter shower pan and cut it down to size. They're made to be cutable, so you'd just take 6" off 2 edges to get your 3x4 pan. This would save you the hassle/dry time of doing a mud bed.

    There may be other cut-able pans on the market, I'm not familiar with them if there are. These Schluter pans require Kerdi over them and a Kerdi Drain to make a water-tight system. Maybe you can use other products with their pan, but I don't know about that, I just use the complete Schluter system, as it was designed to be used all together.

    If you're going that route, you might as well just buy the whole shower kit and get everything in one shot. These generally run about $600.

    Lemme save JW the hassle, and tell you right now that he thinks they're junk, they're overpriced, they're marketing hype, that Jim and I are getting paid by Schluter to hock their junk, etc. Its all bullshit, but that's what you're about to hear.

    Choose the product you like (all of the ones JW likes are good products as well, if installed correctly), and install it properly, and you'll be fine.
    mtcummunins, do you use thinset alone to do the kerdi membrane and base or also chaulking that JW is talking about? Do you use preformed shower curbs and benches or build your own?

  11. #26
    Retired Defense Industry Engineer jadnashua's Avatar
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    If you want a hanging bench, either corner or along a wall, I like the Innovis Better Bench. If you're going to build a Kerdi shower, you could use either Kerdiboard to form it, a monument bench, or something like the BetterBench. There are other companies that make similar products. Using Kerdiboard means the whole bench is waterproof. A monument bench is built inside the waterproofing. The Better Bench is installed after the waterproofing, and can be installed either before or after the tile is installed. Or, you can build the bench out of wood, cover it with ply, then either drywall or backer board, then cover the whole thing with Kerdi while doing the rest of the shower.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  12. #27
    In the Trades mtcummins's Avatar
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    Quote Originally Posted by mcu View Post
    mtcummunins, do you use thinset alone to do the kerdi membrane and base or also chaulking that JW is talking about? Do you use preformed shower curbs and benches or build your own?
    I'm not sure what you mean by "thinset alone," but i like the schluter base, thinsetted down to the subfloor, then kerdi installed over that. I haven't built any huge showers, mine have pretty much all been 30-32" wide, but what I like to do is use basic roofing principles with the kerdi... start at the bottom, run the kerdi horizontally through the corners w/o seams, and overlap the edges bottom to top. This relies very little on the thinset for waterproofing, only wicking can get water past the seam. It does make the overlap area thicker than using the kerdi band, but i prefer this system. Alternatively, you could put the sheet on the wall, band over the edge and up onto your backer board, then bring the next sheet of kerdi down to the top edge of the lower sheet (rather than putting the band on top of the seam, you're lapping it like a roof). This would save you some thickness.

    Anyway, back to the width... one of the things that narrow showers lets you do is run the floor piece up the walls... i center the bottom sheet w/o cutting it to width, cut out the corners, and run the edge of the 39" sheet a few inches up the wall on all edges. Then I add the corners, then bring the first wall sheet all the way to the bottom of the wall. You have to get those corners in tight (squeeze out a bit more thinset than normal), or the buildup can be too much. Again, this is roofing style... don't count on the thinset seams much, but rather the lapping of the sheet.

    It is difficult to manage a sheet long enough to wrap all the way around the shower, but its worth it to me to not have seams in the inside corners.

    I have used the preformed curbs mostly, but I don't think they're necessary if you do a meticulous waterproofing job. You could just as easily, and much more cheaply, build your own. But, the extra time to do that isn't really worth it to me, so I generally just get the $50 curb in the kit and use it. I've not used any of the pre-made benches. I've always had very specific requirements for them, so I like to custom build them. Same thing with niches, they really need to be custom built to be able to get exactly what you want. I'm sure some of the bench options out there are good ones, but you don't want to ask me about that, as I don't have any experience with them. For example, the shower I'm doing next is 5 feet long at the shower pan, but then steps up for the bench, and out an additional foot. This space is suspended over a staircase. Its a maximizing space move, and one that has to be custom made for the application. It's also critical that the bench then gets completely waterproofed, as its not over a pan anymore...

    I like the valve seals and such they offer as well... keep it all sealed up tight.

  13. #28
    ACO Shower Drain Sales johnfrwhipple's Avatar
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    post(s) deleted by John Whipple
    Last edited by johnfrwhipple; 03-17-2014 at 04:33 AM.


    jfrwhipple@gmail.com - www-no-curb.com - 604 506 6792

    Always get construction advice double checked by your local city hall. Flood Test Every Shower - Every Time.

  14. #29
    Retired Defense Industry Engineer jadnashua's Avatar
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    Is 1/8" glass any less waterproof than 1/2" glass? Kerdi passes the ANSI 118.10 test as a waterproof membrane.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  15. #30
    In the Trades mtcummins's Avatar
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    Quote Originally Posted by johnfrwhipple View Post
    It might surprise you that some of Schluter's top men are on these chairs. For example Dale Kempster is Schluter's top tech. Why not shoot him an email and see if Kerdi is OK over dry wall in your shower. Dale Kempster <dkempster@schluter.com>
    Hmm... so you mean to tell me that the top tech at Schluter, who is on a chair of one of the many organizations names that you like to throw around (without referencing anything that actually says what you're claiming), along with all the other Schluter higher ups who are on other boards, allowed the Schluter SHOWER system instructions to specifically list Drywall as one of the proper substrates (and actually the FIRST in the list of substrates), when the organizations they chair supposedly say that it is totally unallowable? Hmm, thanks for convincing me that you're full of crap once again.

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