Kerdi membrane install question.

Discussion in 'Shower & Bathtub Forum & Blog' started by pete c, Mar 10, 2013.

  1. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
    It works fine over Kerdi. Do you need it? Not if you build it properly. Does it hurt? No, except for more time and money. Your house, your money, your time. It's a belt and suspenders thing...your choice.
     
  2. pete c

    pete c Member

    Joined:
    Dec 14, 2007
    Location:
    CT
    I now have most of the kerdi up. Kind of wish I had gone with the cement board as I don't trust my seaming abilities. I am going to go with ardex over them for a little insurance.
     
  3. pete c

    pete c Member

    Joined:
    Dec 14, 2007
    Location:
    CT
    So kerdi col and ardex 8+9 are more or less the same thing? Is there a price difference? If not, I guess I will use the col as I can get it where I bought the kerdi membrane.
     
  4. pete c

    pete c Member

    Joined:
    Dec 14, 2007
    Location:
    CT
    I've seen ardex 8+9 About 80 bucks. I guess that is the way I'll go. Thanks for the hand mixer tip. I'll just have to do it when the wife is out of the house. She'd kick my ass if she caught me doing that!
     
    Last edited by a moderator: Dec 26, 2013
  5. pete c

    pete c Member

    Joined:
    Dec 14, 2007
    Location:
    CT
    Update.

    On john's advice, I went ahead and ordered the ardex 8+9 for a little insurance. Very nice product and mixes well in small batches with the OL's sunbeam handheld mixer.

    Glad I did.

    The stuff rolls on kind of sticky as a second coat. So sticky that in one area it actually started to pull the kerdi away from the drywall.

    This was one of the first wall pieces I installed. Being a newb, I made two mistakes. First off, I tried to use large sheets around corners. Bad idea. They use smaller pieces on individual walls for a reason. It is a PITA to try to go around inside corners. Outside corners seem fine. Second mistake was using big box store Mapei thinset to begin with. The second bag was mapei from my tile dealer. Night and day difference. Same price. The more I shop at real stores, the more I loathe Lowes Depot!!!!

    Sure wish I could backup a few months and do this damn job the old fashioned way, using cement board. The way I originally intended to do it before I let a Kerdi salesman get ahold of me. :mad::mad::mad:

    So, where do I go next? Do I consider this a rather expensive lesson, rip it out and start over with CB and ardex overcoat? Or, do I assume that I did a decent enough job on the rest of the kerdi, repair that section and tile away? The rest does seem to be adhering well.

    To repair, my plan is cut away the bad section, install new kerdi and ardex over it. Is it possible to cut out a section which is about 2 ft square, clean it off and reinstall? I am out of kerdi. I actually was able to return the unused half roll, contrary to what some said. I do have enough band left to seam it.
     
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
    There are a few simple steps for getting Kerdi embedded on whatever approved surface you wish to apply it to:
    - make sure you're using the proper thinset that is properly mixed
    - make sure that you wipe down the surface well with a wet sponge just before spreading the thinset (if you don't, your thinset will skin over way too quick and affect your bond)
    - pull a section of Kerdi back off the wall after you've embedded it to verify that you have a full, even, coat of thinset on BOTH the wall and embedded into the fleece. If you don't, adjust your thinset (probably, mix it properly and be very accurate in the proportions).

    IF you get the Kerdi embedded properly, after a couple of days, there's NO WAY you'd pull that off the wall when applying the Ardex. Done immediately after embedding it, if the ARdex was REALLY sticky, maybe, but still probably not gonna happen.

    A surface membrane is a premium shower. A cbu shower is a cheap copy of a mudded wall with few of the real benefits of that (old, but still good) system. No shower, improperly installed, whatever system is used, is likely to give good results in the long run.
     
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