which waterproofing system for new shower?

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

  1. johnfrwhipple

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

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  2. johnfrwhipple

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

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  3. mtcummins

    mtcummins In the Trades

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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.
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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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/mike2/For%20Liberry%20Stuff/ICC%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.
  5. mcu

    mcu New Member

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    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?
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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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.
  7. mtcummins

    mtcummins In the Trades

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    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.
  8. johnfrwhipple

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

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  9. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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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.
  10. mtcummins

    mtcummins In the Trades

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    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.
  11. johnfrwhipple

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

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    Proper Backer Boards for showers in Pittsburgh, PA

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  12. mtcummins

    mtcummins In the Trades

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    JW, why don't you try reading sometime, rather than just responding with crap.

    http://www.schluter.com/media/ShowerHandbook.pdf

    NOTE: this is the SHOWER, let me repeat, SHOWER installation handbook from your reps that are on all your boards. One more time, this installation manual is for installing SHOWERS, not backsplashes, or whatever else you're claiming w/o any basis. Look at page 2, then look at page 5, then how about page 7, oh, then there it is again on page 9. Oh wait, not done yet, there it is again on page 11. Then there are the pictures on page 12, 14, 15, 17, 19. There's probably a lot more, but I'm already tired of being right.

    I will note one more thing... Read page 19. It specifically talks about protecting gypsum board in a wet zone with kerdi. Hmm... that doesn't sound like the bull crap you've been saying on here...
  13. johnfrwhipple

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

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    Kerdi does wick water as you can clearly see in these pictures

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  14. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    ICC-Evaluation report ESR-2467 was Re-issued August 1, 2011 (and valid for two years). In this, they state Kerdi and Ditra are approved waterproof membranes, and Kerdi in a shower construction is specified for use over various backing materials.

    In it, it specifically states gypsum board (drywall) as one of the backing surfaces IN A SHOWER as required in IRC Section P2709.2 and IPC Section 417.5.2 when installed per the manufacturer's installation handbook.

    Kerdi and seamed Ditra must use an unmodified to seam the materials to prevent latex problems (wetting). Any membrane can leak if you poke holes in it.

    I'm checking on Canadian approvals/restrictions, but that is taking me a bit. Local codes may trump national ones, but in the USA, the IPC testing and approvals exist for Kerdi in a shower over gypsum board (drywall).
  15. mtcummins

    mtcummins In the Trades

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    JW, is it gonna take you 10 years to realize/admit that you are wrong, like it took you 10 years of installing Schluter products to realize that they were "junk"? Just admit it already, you're wrong. That doesn't mean you have to like the practice of installing Kerdi on drywall, or advocate it, but stop making up code restrictions that don't exist, telling us that Schluter does not approve of kerdi on drywall in a shower, and all the other bull crap that you spout off.

    If you actually want to make a difference like you claim, you should stop being a subborn jack***, admit that you were wrong about this issue, and then still explain that you don't think it is good practice and that you think people should not do it for REAL REASONS, not b/c of some obscure code references that don't actually support exactly what you're saying. The way you've acted on this issue, I'll never listen to what you say again w/o questioning it extensively, and getting confirmation from guys like Jim that what you are claiming is actually correct. You will never make a positive difference like you claim to want to by being a dick.
  16. johnfrwhipple

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

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    Checking with Building Departments and Building Bureaus first before selecting backer

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  17. mtcummins

    mtcummins In the Trades

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    You have a very convenient habit of ignoring every code citation that someone makes that proves you wrong. Hmm... funny how you can be "right" when you ignore any evidence to the contrary...

    You have fun with your little mission. I don't believe that you will do anything properly even in that, so your results will be as meaningless as the obscure code references you like to make. Sure, if you call my inspector and ask if drywall is an acceptable tile substrate in a shower, he's doing to say no. B/c of course it's not. Just like your code references, it isn't an acceptable tile substrate. People used to tile greenboard for a tub surround... thats crazy, and against code. All the bullcrap references you've made to code just state that obvious restriction.

    If people want to pay for cement board, i never said anything was wrong with that. I think it is probably a better installation. I never said anything to the contrary. What I did say is that you're full of crap in your statements that it can't be done over drywall.
  18. johnfrwhipple

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

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    Can dry wall be used in a shower - Does the TTMAC ANSI approved it?

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  19. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    John, I don't know if you can't or won't read...the report from a national testing agency states Kerdi and Ditra are waterproof, and lists the associated build approvals. The test had them build a structure, using the manufacturer's instructions, and then flood test it. Drywall is listed as an acceptable backing material IN A SHOWER (although they state it as gypsum board in the document, same thing). If you can't or won't believe the IPC certification, that's okay with me, but when you continue to state that it doesn't work and isn't approved, you're totally off base. From what I've heard, you've been banned from multiple websites for your continued knocking down of products. It's one thing to state you prefer a different brand, but it's another to state a product with approvals is bogus.
  20. johnfrwhipple

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

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    Is Dry Wall allowed in Boston as a backer board?

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