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Schluter-Kerdi shower system

90275 | Posted in General Discussion on June 12, 2007 11:20am

Hi everyone, first time caller.

I have a tile question concerning the Schluter-Kerdi shower system. Saw it demonstrated at a trade show and thought it might be something I could tackle. Was going to use it over 1/2″ hardibacker boards screwed to the stud walls. The Schluter- Kerdi system is applied with an unmodified thinset to bond their waterproofing membrane to what ever substrates you chose for your walls. There in lies the problem. The technician at hardibacker would not get behind the thought of using an unmodifing thinset to adhere the waterproofing membrane to their backer board and Schluter says that using a modified thin set will never dry correctly and should not be used in their system. Is it that bad to use an unmodifided thinset in a shower stall tiling job if propper installation technques are used. Will the tiles start popping off the walls in a few years?

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Replies

  1. User avater
    EricPaulson | Jun 12, 2007 12:23pm | #1

    Why don't you do what they want you to do in order to obtain predictable results rather than perform an experiment with unforseen results.

    What you are asking is; "has anyone here ignored the instructions in this particular manner, and what were the results?"

    I believe Schluter has allready discovered the results for you and as such, written an instruction booklet for their product.

    Hardi board sucks in my opinion for tile work.

    Use either CBU or sheetrock.

    Eric

    [email protected]

     

     

     

     

  2. Saltworks | Jun 12, 2007 02:42pm | #2

    I think you will find that Schluter requires that you use the thinset specified for the substrate, which will often be latex modified thinset, but they require unmodified for the tile to the membrane.  I have built two showers over drywall using unmodified.  When I have used Ditra for floors over plywood I use modified for the Ditra and unmodified for the tile.

    You can find out a lot more about Schluter products at http://www.johnbridge.com

  3. User avater
    Gene_Davis | Jun 12, 2007 04:20pm | #3

    Schluter's US HQ and distribution center is 40 minutes up the road from me. 

    They pretty much own the market here, and drywall is the wall substrate for the huge majority of builders and tilesetters.  Hardi, blueboard, Durock, etc. are all not needed.  Kerdi is waterproof, period.

    Follow their instructions.  Don't try to be a pathfinder.

    For some great installation photos using Schluter Kerdi and Ditra, go to the more recent posts on the thread "Small Addition," seen here at Breaktime in the "Photo Gallery" section.

    And the earlier post is correct.  There is a far larger resource for you: The John Bridge forum.

    1. timkline | Jun 14, 2007 09:52pm | #9

      Kerdi is waterproof, period.

      That's quite a statement.  You put a lot of faith in the system by installing it over drywall, a substrate that will disintegrate when it gets even slightly wet.

      What's the difference in cost of CBU vs. drywall in a typical shower stall ?  $100 - $200 ?

      I can't imagine why anyone would ever take the risk of drywalling a wet area.

       carpenter in transition

      1. paulwaterloo1 | Jun 14, 2007 11:25pm | #11

        I used drywall on my Kerdi installation, and would continue to do that. If water leaks behind it, it doesn't matter what you have, it will crumble sooner or later.

        1. Piffin | Jun 14, 2007 11:59pm | #12

          Concrete crumbles when it gets wet?I better hurry up and move that pile of cement board I had out by the shop all winter.;) 

           

          Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

          1. paulwaterloo1 | Jun 15, 2007 12:44am | #13

            If you've ever done a Kerdi system, you would realize that you are basically putting the wallboard up.....then a layer of cement, then the Kerdi membrane, then another layer of cement and then the tile. And you put additional layers of cement for all corners, etc.

            So there is no reason to put cement board up in the first place.

            I'm not a contractor, just a guy who likes to do things in detail and try to make sense of it. And it makes no sense to put up cement board. This system is far superior to just putting felt up or a rubber membrane in the bottom and 12" up around the side.

            But I guess time will tell if it leaks!

            Cheers!

          2. Piffin | Jun 15, 2007 12:59am | #14

            Lemmme tell ya why it makes sense then.BTW, I was just playing with you on cement board crumbling when wet - it won't. But Sheetrock or green board will.Your supposition that the shower wall with Kerdi is waterproof is true as far as plain straight walls goes.
            But you have several penetrations for showerhead, valve controls, and sometimes a recessed soap or accoutrement dish. Every old tile job I have ever demolished or repaired had lots of water sign and or water damage where the fill spout and valve body were mounted through the wall. It is simply a fact that you will never make that perfectly watertight. so your greenboard there behind the Kerdi will get wetted. And if you ever have a leak in that wall - not at all uncommon - the whole of the backside will be wetted.Will any of this be enough to cause troubles for you? At this point, only god and the water nymphs know, but it is possible for you to have a floppy wall there someday. With cement board instead of greenboard, it is not possible just from wetting it front or back. 

             

            Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

          3. paulwaterloo1 | Jun 15, 2007 01:25am | #15

            You are right.....I thought the same things.....ran the Kerdi into the openings.....and there are good gaskets on the Grohe stuff I bought......

            I knew you were joking!

            Sometimes I post and read here and realize that since most of the things I do are for the first time (and a lot the only time)......that I am wrong in my "perfect" method.

            The wall around the controls doesn't hardly get wet at all when you are taking a shower....

             View ImageYou can see where I put patches around the openings, I folded the Kerdi over the wallboard for the same reason you state. I should probably just post naked pictures of my woman in the shower and call it a day! :-)View ImageView Image

            Edited 6/14/2007 6:30 pm by PaulWaterloo

          4. john_carroll | Jun 15, 2007 02:12am | #16

            Very nice tile work, Paul. I have no doubt that it's impervious to water from inside the shower. However, the supply lines are on the other side of the substrate from the membrane. I would rather spend a few extra dollars and a few extra hours for a cement-based substrate, in case there is a problem in the plumbing.

            Like you, I used Grohe fixtures. One of the nice features of the mixing valve I used is that it can be accessed from inside the shower. When the shower head dribbled rather than flowed, I found that debris from the supply line was built up in the screen at the valve. (Words of advice: Never use whole wheat bread to plug the supply line during a plumbing rough-in!) The repair was straightforward but about a gallon of water ran over the edge of the cement board. I was glad it wasn't gypsum.

          5. Piffin | Jun 15, 2007 02:20am | #17

            It looks really good, even without the naked woman!
            ;) 

             

            Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

          6. kjblunck | Jun 15, 2007 06:31am | #20

            Paul,

            Great shower.  I have a question for you regarding the window.  My shower renovation project also has a large window in it and I am trying to figure out what to do with it.  I don't need an operating window, but I can't really do away with it without re-siding my house.  I noticed in the original space your window was wood, possibly trimmed in oak.  Did you replace it, and if so with what?  When I talked to the window guys they made it sound like neither vinyl or aluminum painted very well and I really don't like the idea of a wood window in a shower.  Even painted, they ultimately always peel...Any suggestions?

          7. User avater
            EricPaulson | Jun 15, 2007 12:52pm | #21

            vinyl window

            extension jambs and casing (if needed) from Azec or similiar.

            caulk with 3m Marine Adhesive

             [email protected]

             

             

             

             

          8. paulwaterloo1 | Jun 15, 2007 03:45pm | #22

            The window you see installed is a new window, not know much about windows (and knowing a wanted a good, quality wood window, not vinyl), I bought a Jeld-Wen AuraLast window. It's alumuinum clad on the outside and wood that is treated on the inside, guaranteed to last 20 years.

            http://www.jeld-wen.com/windows/wood/builders/product.cfm/product_id/177

            I painted it with one coat of oil based primer and then two coats of oil based paint. It doesn't get water in the jamb, due to its location.

            I had a cheap owner who lived in my house before me, so I have T1-11 siding on my bungalow, I replaced two panels during the install.

            This replaced a glass block window from before. The location of the glass block window is now where the wall with the shower controls jets out.

             View ImageView ImageView ImageView ImageView Image

          9. kjblunck | Jun 15, 2007 07:36pm | #23

            Paul,

             

            Thanks for the information and the web site.  They look like just the windows I am looking for.  I think they might even have one to fit my opening.  Juddging from the pictures, it looks like your install was even more difficult than mine; I'm trying to avoid having to replace siding because I don't think I can easily find siding to match the 90 year old stuff on the house.

            I noticed from this set of pictures that you had an old hot water radiator for heat .  I assume you took that out.  What did you do about heat?  I was thinking about radiant under floor but it is expensive...I might just cut a hole in the floor for forced air or install an in the wall electric heater (cheap).  Haven't made up my minde yet.

            Again thanks for the information.

             

            Kurt

          10. paulwaterloo1 | Jun 15, 2007 07:47pm | #24

            Relatively cheap and realitively easy? In floor heating with electric mat. It keeps the floor warm and it doesn't necessarily heat the room, but if adjacent rooms have heat, you are good to go, especially with a window like that and new wall insulation. My bathroom was super warm this winter (more so than the last two with the old window and leaky vent on it) with NO heat on. But you will need a new separate circuit for it.

            I installed warmboard, but will have to hook it up some day.....when I redo the adjacent kitchen and remove the radiators, I will be hooking it up.

             View ImageView ImageView Image

    2. john_carroll | Jun 14, 2007 10:34pm | #10

      "Kerdi is waterproof, period."

      Probably true. But I was glad I used Durorock on my last job. The mixing valve got clogged and had to be flushed. A lot of water went onto the cementboard during the repair--without any problem. It might have been different had I used DW. 

  4. davidmeiland | Jun 12, 2007 04:33pm | #4

    Quite a few installers report using a lightly modified thinset like Custom Versablend with Kerdi, no problems, either to bond to the wall or to bond the tile. Done it myself, in fact.

  5. Piffin | Jun 12, 2007 07:06pm | #5

    My memory is that they recommend using the right thinset FOR THE SUBSTRATE OR UNDERLAYMENT that you are adhering to, then use unmodified for the tile itself.

    On one small job, I did use modified for the tile - small octagon ones - and it cured nice and strong but did take a few days to cure up. I think with larger tiles, it would have taken over a week.

    I know that it did cure well, because I forgot something - had to cut the hole fore the toilet flange after wards so I saw how hard it was!

     

     

    Welcome to the
    Taunton University of
    Knowledge FHB Campus at Breaktime.
     where ...
    Excellence is its own reward!

  6. Schelling | Jun 13, 2007 02:17am | #6

    I second the recommendations you have heard  to follow the recommendations offered by Schluter.

    We have used modified thinset with perfectly satisfactory results. When we did this we were following the recommendations of the Schluter tech rep who is a personal friend of ours and who used to do all of our tile work using traditional mud bed techniques.

    From listening to him I can tell you that Schluter ( and any other decent company) listens when someone has a problem with their products. Usually the problem comes from someone not following their recommended procedure but occasionally it is the fault of the product. With most of us here, we would just have to suck it up but the large tile installers can get satisfaction if it is the problem with the product or procedure. Schluter is constantly updating their procedures in an attempt to completely eliminate problems that are their fault.

    The use of unmodified thinset to set the tiles is just such a procedural change. It would only take one mall job that had a sporadic but consistent failure that would make this change worthwhile. We are the beneficiaries of this ongoing research. It would be foolhardy not to take advantage of it, even if 99%of the time it would not make any difference.

  7. paulwaterloo1 | Jun 14, 2007 05:10pm | #7

    I used the modified thin set (the one least modified) that you can buy at Home Depot....you start looking around and it's hard to figure out what modified is and what non modified is.

    Some have a high level of additives that you know are modified, and the unmodified has the lowest strength numbers on it. I used the one that had higher numbers......I thought I had a picture of it, but not handy.

    When I set my tile, they were very small mosiac and I used a very small trowel. It was weeks before I grouted them.....so I'm sure the thin set cured. If you had a 12" tile and wanted to grout the next day (which I wouldn't do anyways, I think I would always let the thin set cure a week before grouting based on my NON scientific thoughts in my mind).......then nothing would really dry.

     

    View Image

    After looking at that picture....I'm glad to have this WAY behind me!

    1. Piffin | Jun 14, 2007 06:32pm | #8

      All those little mosaics!!!
      Are you sure you didn't leave a little sanity behind? LOL"it's hard to figure out what modified is and what non modified is."The unmodified is primarily a Portland based that cures like any cement or concrete - thru the chemical reaction that sets it in place.Modified uses the addition of latex compounds to change the properties. Latex is both a rubber and water based, in its native state. Adding latex modifiers changes it to a compound that has to dry instead of setting chemically. The rubber-ness also makes it stickier, more workable, have a longer working time, and more freeze thaw stable, both while setting and alter. The down side is that since it needs to dry to air, giving off much of its water, having replaced the water in the chemical reaction with the rubber latex, it will dry extremely slowly when locked between a non-porous tile and the non-porous barrier behind. The larger the tile, the longer the set time will be.For simple comparison, you can take yourself some leftover modified and shape it into a softball size and shape. Do the same with some un-modified. In a couple of days, the un-modified is likely to be a solid chunk, but a week later the modified is still likely to be soft and pliable in the center.Using the modified for thee tile under my small tiles on the floor was of less concern. I had time, the grout lines allowed vapour transmission for drying, and on the floor, the tiles weren't going anywhere.But I would have been a fool to use modified for the 17" tiles on the wall. They would have prevented air getting to them, and while remaining pliable fro a long time, the heavy tiles might well have slipped and sagged off or down the wall 

       

      Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

      1. seb | Jun 15, 2007 05:00am | #18

        <For simple comparison, you can take yourself some leftover modified <and shape it into a softball size and shape. Do the same with some <un-modified. In a couple of days, the un-modified is likely to be a <solid chunk, but a week later the modified is still likely to be <soft and pliable in the center.That is very interesting.....Answers a question I have had for a year or so...I had some leftover chunks of modified that I put in the trash...a week later it was still soft....I thought,, Of course it is a setting product like concrete...Hummm...But it wasn't,,,,The answer!!!
        Thanks!...
        Bud

        1. andybuildz | Jun 15, 2007 05:05am | #19

          I used Versabond...its not "as" modified and i found it to do a really good job. I'd use it again.

           

          "What people will notice and remember is the broad brush of how how we act.We can aspire to reach our high ideals, or we can slide down the slippery slope towards the despicable." rjw

          http://www.john-lennon.com/imagine-neilyoung.ra

          http://WWW.CLIFFORDRENOVATIONS.COM                                 

           

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