Why does drywall work in a Kerdi Shower?

Discussion in 'Shower & Bathtub Forum & Blog' started by jadnashua, Jan 26, 2014.

  1. DougB

    DougB Member

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    John,

    I have done a lot of showers (3) and I've found some really exciting things to share with you.

    First my main concern was the cost of the drywall behind the Kerdi. I mean you can spend $30 - $50 dollars for that drywall. Well I've solved that problem!

    The other day I was at the liquor store. Ya know, they have a lotta boxes... Well I got a boat load of them, and took'em apart real careful (it's more relaxing to listen to some Deliverance music). So I stapled the boxes to the studs - did two layers, and made sure not to overlap the seams.

    Then I had some left over varnish that my son hadn't huffed - and applied it to the cardboard. I figger a nice waterproof substrate. So right here you've saved over fiffty dollars!!! Then that unmodified thin set ( hey it's 1/2 price cause it was 5 yrs old) - stuck that Kerdi real gud.

    I mean since the Kerdi stuff is waterproof - ya can go right over dat cardboard!

    And hey, it worked! We've been using the shower for a couple a days, and everything is fine. We may even put up some tile.

    John, don't feel too bad gettin' adivice from a fella like me. I'm sure in time you'll be expert like me.
     
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    And, where is that an approved, tested backer material? Just more BS, like John trying to do a bonded mudbed over a decoupling membrane - use the products as they were designed, and they work. Choose to do it otherwise, and all bets are off. Should you question your ability to do it per the instructions, build it better. Don't trust the materials, use something else. Invent your own, be prepared to back it up like the manufacturers do with testing, training, support, and their money. Talk is cheap, the advice I give is based on the manufacturer's instructions. If you don't believe me, read them yourself.
     
  3. DougB

    DougB Member

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    All kidding aside - and I do a lot of it. John is a real pro - and he has a lot of real world, documented examples, sucesses.

    Then come's some 'tool' like Jim, who doesn't know what he doesn't know. Shoots off his mouth. Actually, I'm not going to feed the Red Shoe troll any more. He can post whatever he want's. If he gets no response, he's outta gas.

    As an aside, the Red Shoe is really a spolier. He's all over the internet. If you ask a question he gives his half assed opinion - and thus spoils other more qualified responses.

    I'm with John - that John Bridge form with CX - that's artificial - a broken record - 'follow the manufacters....'. I can see the change in that forum from 3 years ago when I went there for advice for my last bathroom.
     
  4. DougB

    DougB Member

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    Really Mr Red Shoe. Do you understand that was all a joke? Not understanding humor is one of the first signs of a serious mental health issue. I do not say this as an insult - my wife does this stuff for a living.
     
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    I saw it for what it was...not everyone reading this will.

    Companies that have been in business for a long time rarely propose bogus solutions to the use of their products, especially one that has been in use for decades...lots of successful outcomes when there is a reasonably workman like install. That a product can fail if it is not used properly should be a given. To point out or express that it is certain to fail without any substantiation is wrong. All the examples of drywall failing when not used according to an accepted, tested procedure with thousands of successful results and independent test results showing it working is just wrong. There is more than one way that has been tested and approved to use Kerdi to make a shower, but it is up to the installer to decide what he is comfortable to use, but any of those materials will work. If you don't trust your plumbing skills, a cbu backer may not prevent eventual failure, as a slow leak could easily end up with the floor and studwalls rotting out before you noticed. Not counting that wet wood is a magnet to carpenter ants and termites which bring their own problems.
     
  6. dhagin

    dhagin builder:anti-builder

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    Just curious... has anyone ever seen a Kerdi shower, properly installed over drywall, that failed? :)

    I haven't.
     
    Last edited: Jan 31, 2014
  7. dhagin

    dhagin builder:anti-builder

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    No Kerdi failures? Anyone? :)
     
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    The suggested answer, should you choose to check verses bashing everyone for no cause, is to tear the foam pan out and start over. As opposed to here, where John Whipple thinks he is the only one that should give advice, there are LOTS of people, well qualified, that can and do offer advice on www.johnbridge.com. And, when they give that advice, they don't do it in insulting and promoting themselves as superior and the only one that knows anything.
     
  9. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    I do not read every message on every board. I also do not read messages from you - why would I, the most I get from you is insults.

    In the situation above, the OP failed to follow the instructions when installing a foam tray - he tried to install it over a non-level subfloor. The instructions clearly say to ensure the floor is level before installing it. He tried to do it with thinset, then stood on the thing to embed it and do other work...well, what you'd expect happened...it sunk, negating the effort to do it his way, rather than the way the instructions said. Sort of like John Whipple not following Schluter's NA instructions. I wonder if he ever thought about the fact that thinsets in the USA meet one spec, and those sold in Europe meet a different one. The manufacturer's instructions differ because the materials differ...but, to extrapolate that to infer that the NA instructions are inadequate, is not a valid, logical result. What is logical is that the manufacturer tells people how to install their products with the materials available such that the end result is reliable. Creating fear and uncertainty is one way to make yourself look superior, when in fact, it has no substantiation. I've been trying to get a copy of the European thinset specification, but I'm not willing to pay over $100 for it...I'm still looking. What I expect is that the filler size (sand, etc.) and minimum cement volume in the thinsets sold between the NA and European markets differ, and that given the specs, thinset alone cannot make a fully reliable, waterproof seam in Kerdi with the European spec thinset like it can in the USA, and in order to ensure it is waterproof, they call for seaming it different.

    But, John takes the difference to infer and promote question that one is superior to the other.

    If I do get a copy of both specs, I'll try to summarize the differences in a separate thread. But, in the meantime, I believe the manufacturer knows his product and what it takes to make it work...John doesn't. Thinsets in the USA are rated according to A118.x and in Europe according to BS EN 12004.
     
  10. dhagin

    dhagin builder:anti-builder

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    Since no one around here has ever seen or heard of a Kerdi Shower failure, a thread was started over at John Bridges site. All this talk of drywall failure as an academic exercise is all well and good, of course, but unless there are actual failures it's a solution lookin for a problem [that simply doesn't exist].

    Here's a link to the thread at John's site. :)

    http://www.johnbridge.com/vbulletin/showthread.php?t=111300
     
  11. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    For those that aren't keeping up, the Kerdiboard failure was in a steam shower, likely where a steam line was too close to the board. The manual calls for a max temp around Kerdiboard of about 170-degrees (I'd have to look up the exact number, but that's close). Steam, boiling water, happens at 212-degrees at sea level. And, steam could be hotter than that once it is a gas, there's no practical limit on the temp it can raise. As far as I know, no final outcome on that situation.

    There's no evidence of an actual failure in the stone like shower shown, either. If that area is where the spray hits the wall, a natural stone can become saturated. There's no evidence that there is any leaks to the outside or structural failure.

    A foam Kerdi shower pan, if you read the instructions, says prior to installation, the floor must be level. Because you stand on the thing to embed it into the thinset, it is essentially impossible to try to level it with thinset and get a good bond to the substrate. Trying to level the pan afterwards is a very difficult thing to do, and the time involved and the reliability of the fix afterwards is beyond the scope of most DIY'ers, thus the recommendation to tear it out and start over.

    With the unprotected drywall, no question, that's just dumb. The difference is day and night. Done right, a Kerdi shower doesn't leak. Mold takes three things, eliminate any one, and it does not occur: moisture, food, mold spores. Kerdi, done right, eliminates moisture from anything behind it, and since it isn't food, nor is mortar or tile, mold will only happen if things aren't kept clean, and then on the surface...that can happen on ANY shower, regardless of how it is built.
     
    Last edited: Feb 4, 2014
  12. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    More pictures of tile directly on drywall...anyone that knows anything expects them to do nasty things if moisture is involved, but again, once covered with Kerdi, a waterproof material, it's no different than the drywall on your ceiling under your roof, or that on your walls next to the windows or doors. When installed properly as a system, the drywall never gets wet. http://www.schluter.com/media/shower-handbook.pdf?v=201401311539 I didn't make the recommendation up...Schluter did, and feels strongly enough about it to have had it tested and certified as waterproof by a well-respected testing agency, and backs it up with a decent warranty AND HAS BEEN DOING IT THIS WAY IN THE USA FOR DECADES. In the process, they also built waterproof showers with cbu and a few other materials, all called out in the referenced link, should you not trust yourself. But, if you didn't trust yourself to do it right, or don't want to read and understand their instructions, you may want to use a different material. A conventionally built shower can perform well, but loses the advantage of limiting any moisture to right under the tile like in a Kerdi shower. Lots more conventional showers can be found that have leaked if you look around than Kerdi ones, simply because it is not all that hard to build one that does not leak.

    Schluter is the only company with the long track record of successful showers done per their instructions (over 20-years), and believes enough in their product to safely make use of the less expensive, more easily installed material. The do not tell you you MUST use drywall, but that you can, and have a successful installation. Why spend money on extras when the success rate is identical, it goes up faster, and the end result comes out the same...a waterproof shower. I've said more than once, you do not have to use drywall in your shower when using Kerdi, but that you safely can if you are anywhere near a bit handy and can read and understand the pretty simple instructions and general guidelines on its use.
     
  13. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    A failing shower is one that leaks...there is no evidence that it is leaking. If that area is where the majority of the spray hits, it may just be that that tile is saturated, which is no reliable indication that there is a leak anywhere. Not all tile is equal, especially with natural stone.
     
  14. eurob

    eurob master tile and stone installer

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    Not all waterproofing membranes are created equal , especially a sheet membrane -- Kerdi -- . Different rates of absorption and combine with the unmod mortar -- another thirsty one when dry -- , the drying time is ....like natural stone . Add a sealer on top of it , water will just accumulate .

    If leaks are the only thing that matter in a properly build shower , then I think the mirror is needed...........
     
  15. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    The Kerdi is waterproof. If that tile is hit by the concentrated shower spray on a regular basis, the tile itself could become saturated. If this were say a conventional shower with cbu behind it, it would wick water more, and a larger area would be wet. Some stone absorbs a fair amount of water, and it can take it weeks to dry out. The choice of the tile may be suspect, but it has nothing to do with whether the shower is defective from a functional viewpoint. All the membrane does is prevent moisture from getting behind it...what you put on top of it can get wet. With a dense porcelain, the tile would not change color. If the showerhead were moved a bit, that one may not get wet. It does not indicate a leak in the shower with the information provided.
     
  16. pete c

    pete c Member

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    Good to see the battle is still alive!!!!

    As you may recall, I wandered into this forum months ago after the horse was already out of the barn, so to speak.

    i had just spent a good deal of time and money, installing a drywall/kerdi walk in shower. I did this after being sold on the idea by the tile store salesman. As iIput up the kerdi, I realized that i might be in trouble. Being a DIY homeowner and not a tradesman, my application technique was questionable. That is when i came in here looking for advice. John told me to cut my losses and rip it out. i probably should have listened. i ended up taking some of his advice and did an ardex 8+9 application over the kerdi. good stuff that ardex and wayyyyyyyyyyy cheaper/easier to apply than kerdi.

    i am now in the finishing stages of tiling. i am keeping my fingers crossed that i will be OK, but, looking back on it, it's a no brainer. ardex over CB is the way to go. much cheaper, easier to do AND if, somewhere there is a breach and water does get through in small amounts, it may be just fine, especially if there is any sort of air flow at all.

    i have just one question. why use a drywall/kerdi system over CB ardex? it is much more expensive and if it fails, even slightly, it will turn to shit in short order, whereas the CB/ardex may be just fine.

    OK, I have one other question. why didn't i find this thread before i bought the kerdi?
     
  17. pete c

    pete c Member

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    at best, material cost is a wash. i think the kerdi is more, personally. as for speed of application, i guess drywall night go up a bit quicker, but, not much. with the kerdi application, i have found out the hard way that you better know what the hell you are doing. ardex? mix and roll. an f-ing caveman could do it.

    advantage, ardex, especially if you are an amateur. and as you say, if water does find a way through, and it very well may, the CB has a fighting chance. the drywall, not so much

    damn, i wish i could rewind a year and do this over. that shower would have been done a long time ago.
     
  18. dhagin

    dhagin builder:anti-builder

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  19. dhagin

    dhagin builder:anti-builder

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    Remember folks, a photo of wet tile is not a Kerdi failure. Need more info: to begin, what does the structure consist of - wood, concrete, steel, other? is the shower floor sloped? how much? is their a mortar bed or foam shower pan? etc... these are just a few of the first questions we need to evaluate a shower failure. Any shower failure. Just trying to help you all understand a simple, professional installation where drywall has been used successfully for decades.

    Folks can choose to ignore facts, that drywall as a substrate in a Schluter shower system is a fine professional and code approved installation, all they want. I choose to live in a fact based world where long term successful results inform current and future trends. Have fun all. :)
     
  20. DonL

    DonL Jack of all trades Master of one

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    Yes you are correct, May I get a Bump Please ?

    Thanks in advance.


    Pissing_Contest.jpg


    Have Fun Everyone.
     
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