Kerdi membrane install question.

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

  1. pete c

    pete c New Member

    Messages:
    52
    Location:
    CT
    I am building a walk in shower. the Sheetrock is up, time to start putting up the Kerdi.

    In demo video, they band all corners and lay sheets cut to each wall. Is there any reason I can't use single sheets to go around corners? I understand placing each sheet will be a bit more work, but, it would seem to me that fewer seams is better and also saves a little material. I was wondering if maybe it had to do with the thin set setting up very quickly, allowing little time to fuss with the kerdi.

    Or maybe Schluter likes selling Kerdi Band!
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,321
    Location:
    New England
    It's much easier to use smaller sheets than to try to go around a corner. While Kerdi-Band is thinner and makes for a smaller buildup, you can use a band of the Kerdi material...it would depend somewhat on the tile you used whether that would be an issue. The last thing you want is to have the thinset skinning over before you get the last but up. Depending on the wall width, I've also not cut it, run the edge of the sheet around the corner instead of using the band material.
  3. johnfrwhipple

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

    Messages:
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    Location:
    North Vancouver, BC
    Install Answers for Kerdi Membrane - TCNA and TTMAC do NOT allow drywall in a shower

    I have deleted all my posts showcasing Kerdi, Ditra and the like from Schluter Systems. I have stopped using these products and do not recommend them now to my online clients, my local customers. You will not see photos here going forward. No one asked me to delete these photos. No one told me to delete them. I feel these products from Schluter come with far to many restrictions and that the testing of the products leaves lots to be desired.

    It was my testing of the niches and resulting phone call to review my findings that finalized my decision to switch to a more premium waterproofing approach a quit using Schluter's products all together...

    If you need help with a Kerdi Question email Dale at DKempster@schluter.com - this is Schluter's top tech. Remember that Jadnashua (Jim) here on Terry's forum is not in this business and by my account works to privately promote Schluter and the John Bridge Tile Forum.
    Last edited: Jun 20, 2014
  4. pete c

    pete c New Member

    Messages:
    52
    Location:
    CT
    john, that was my thought as well, but the kerdi dealer says sheetrock is fine. i think it might have to do with the cement board sucking the moisture out of the thinset too quickly.
  5. johnfrwhipple

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

    Messages:
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    Location:
    North Vancouver, BC
    Should drywall be used under Kerdi Membrane in a shower build? - Answer: No

    Post(s) deleted by John Whipple
    Last edited: Mar 15, 2014
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,321
    Location:
    New England
    If you install Kerdi properly, the drywall stays as dry as it does in any room. A failure of your plumbing, while always possible, could damage it. But, a failure of your plumbing in any area of the house is problematic. Just do it right, and it should outlast the house.
  7. johnfrwhipple

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

    Messages:
    4,843
    Location:
    North Vancouver, BC
    Installing Waterproofing over Sheetrock or Drywall

    Post(s) deleted by John Whipple
    Last edited: Mar 15, 2014
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,321
    Location:
    New England
    To be fair, almost none of the 'showers' being shown in the demos are real...they're mockup walls and floors, intended to show the application of the membrane, not the structure of the house.
  9. johnfrwhipple

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

    Messages:
    4,843
    Location:
    North Vancouver, BC
    What is the best drywall to use under Kerdi? - None - use a cement board

    Post(s) deleted by John Whipple
    Last edited: Mar 15, 2014
  10. johnfrwhipple

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

    Messages:
    4,843
    Location:
    North Vancouver, BC
    What product is easier to apply over drywall? Kerdi or Ardex 8+9

    Post(s) deleted by John Whipple
    Last edited: Mar 15, 2014
  11. DougB

    DougB Member

    John,

    I'm remodeling a bathroom, with an drop-in tub/shower in an alcove. I'm using cement board. Is there any advantage of using the Ardex product instead of Red Guard or Hydroban?

    For the rest of the bathroom, I was planning to use regular drywall, and tile over that. Is tiling over drywall OK? Should I prime the drywall first? What do you do?
    Last edited: Mar 13, 2013
  12. Amish Electrician

    Amish Electrician New Member

    Messages:
    17
    Location:
    Arkansas
    Pete, I don't mean to 'pile on,' but .... NO GYPSUM in the shower! Not even the green or blue stuff!

    Yea, I know, various vendors make various claims. Read the fine print. There's a lot of 'maybes' in there. Murphy's Law will ensure that something goes wrong.

    I'm not a plumber; I do electric work. Several of my customers are property-management firms, so I get to see plenty of remodel work. I have yet to see a any gypsum product, any tile job, survive.

    So, when I do my bath, it will be cement board 100%, even on the ceiling. If nothing else, the cement board won't dent when you hit it with a mop handle. No paper or glue to feed mold, either. Skim coat it with real plaster, and it's as waterproof as steel plate.

    FWIW, my walls are getting covered with FRP (fiberglass reinforced plastic) sheeting. Absolutely waterproof, with very few seams - and none of the seams are horizontal. It's that pebbly stuff you see in commercial kitchens and public restrooms.

    Maybe I'm over-doing it, but the difference in materials cost is not that much. It amazes me that folks will spend a fortune on getting just the 'right tile,' yet compromise on the basic structure.
  13. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,321
    Location:
    New England
    Kerdi is a waterproof membrane. When it is installed properly, once you protect it with tile, no moisture penetrates it. John is a belt and suspender kind of person. Being in a business where you never want callbacks, it has some merit if people are willing to pay for it. Schluter has paid for an independent testing of Kerdi membrane installed over drywall and it passes all industry specifications for moisture protections IF IT IS INSTALLED PROPERLY. In my 60+ years, I've never had a belt or suspender fail, and have never worn both. You either believe the manufacturer and the testing, or you don't. They do not force you to use drywall, they also list other acceptable materials, which includes cbu. You use what you feel comfortable with and local regulations require. There are thousands and thousands of Kerdi showers in use today applied over drywall that are as dry as the day they were built. If you have a leak, it's either because of poor workmanship or an accidental puncture that occurred after testing and before tile. A leak would require fixing whether it was cbu behind it or drywall whether it was through the membrane or from a plumbing leak behind it. If you don't believe a single layer waterproofer is sufficient, then you'd want cbu on your walls and especially next to your windows in all the rooms of your house, or make the walls poured concrete. A house exposed to rain driver gale and hurricane force winds is a much more hostile environment than a shower. I trust my shingles and paint on the outside of the house to protect the interior walls as I do Kerdi to protect my shower. Feel free to augment it if it makes you feel better. I've got the certification test document somewhere, but you can find a copy on-line if you look. Since the test is only valid for a few years, it gets repeated, and has always passed. Most local inspectors will allow installation to the manufacturer's instructions with that certification. Some won't, and then you do what you have to should you want to use that material. There are lots of choices, pick one you're comfortable with, but installed properly per the manufacturer's instructions, they all work. Some give you more margin for error than others, but if you trust your workmanship and workplace environment to not compromise it, that's somewhat irrelevant. FWIW, in the USA (don't know what the duty is to Canada), you can pick up Kerdi membrane for around $1.75/sq ft fairly easily. Many places offer free ground shipping. Also, if you believe the websites selling it, list price is in the order of $1.91/sqft. Canada can have some high tariffs on things, so your pricing could vary considerably as well as shipping.
    Last edited by a moderator: Jul 16, 2014
  14. johnfrwhipple

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

    Messages:
    4,843
    Location:
    North Vancouver, BC
    Kerdi Cost $3.00 per square foot @ Home Depot in Vancouver

    Post(s) deleted by John Whipple
    Last edited: Mar 15, 2014
  15. Amish Electrician

    Amish Electrician New Member

    Messages:
    17
    Location:
    Arkansas
    OK, Jad, I won't debate your religion with you.

    "IF" is the biggest word in the language. Heck, I'd win the lotto IF I pick the right numbers. IF the Queen had balls, she'd be King.

    BTDT.

    So go ahead, get by with the minimum possible. I'm confident you also wear Wal-Mart $8 sneakers and drive a Yugo ... after all, they meet all the same regulations as the expensive name brands, so they must be just as good.

    While you're fumbling through all that documentation ... I seem to recall seeing somewhere that there were model codes that banned drywall and greenboard from 'wet' areas, like showers- no matter what was over them. You might want to be sure ... and get the permit and inspection as well.

    Everything I need to fix in my house is the direct result of someone being 'smarter' than the rule book.
  16. DougB

    DougB Member

    Hey, what's wrong with a safety factor of .9?? :)

    Here in Minneapolis we had a 1965 POS bridge (I 35-W) over the Mississippi. It was a bare bones design, a nightmare. Every year the state had it inspected cause it kept rusting - until it collapsed (5-6 yrs ago) with about 40 cars on it. Killed some people, maimed others. But it passed inspection. Cost the state some nice $change$.
    Last edited: Mar 14, 2013
  17. DougB

    DougB Member

    I would ask you: How many Kerdi showers have you installed?
  18. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,321
    Location:
    New England
    Personally, I've installed several, seen many more installed, and in contact with people that have installed many hundreds. Some argue that paid testing is biased. But, if you believe that , then you'd ignore any UL, CSA, IAMPCO, or other testing that is paid for by the manufacturer. I don't put storm windows over my windows, or an awning over my roof, to give things a second waterproofing layer...I believe, that properly installed, they can do their designed job, as I do believe Kerdi works as designed. I don't care what you use, if it is not installed properly, you can have problems. I happen to drive a BMW, but that should be irrelevant to the issue. I'm not adverse to spending more for better things, but at some point, more doesn't buy you anything except a smaller bank account, personal preferences aside.
  19. pete c

    pete c New Member

    Messages:
    52
    Location:
    CT
    Wow, looks like my thread came back to life in a big way this past week. Here is where I stand.

    My shower is drywalled, ready for the kerdi. Haven't hung a single piece yet. Have an expensive roll of it sitting here waiting. I bought the entire roll with the understanding that I can return any I don't use.

    My gut feeling, even as I was hanging the drywall was that it was a bad idea, but the kerdi dealer was adamant that drywall is the way to go. I now realize that maybe this is a marketing strategy. Kind of their way of saying their product is infalible.

    So, do I rip out 50 bucks worth of drywall to avoid later ripping out a thousand bucks worth of tile/kerdi or do I continue taking great care to do it right? I am kind of leaning towards moving on and just making sure I do it right. And crossing my fingers!!!!

    So, did I read right that a coat of drywall primer would be a good idea? BTW, the mortar I have is Versabond fortified thinset. I bought it from Ace hardware.

    Recommendations on primer or anything else are greatly appreciated. Thanks for all your help.

    Pete
  20. johnfrwhipple

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

    Messages:
    4,843
    Location:
    North Vancouver, BC
    Best backer for kerdi membrane - Concrete board not drywall

    Post(s) deleted by John Whipple
    Last edited: Mar 15, 2014
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