What actually does an uncoupling membrane do?

Discussion in 'Shower & Bathtub Forum & Blog' started by jadnashua, Apr 4, 2014.

  1. johnfrwhipple

    johnfrwhipple BATHROOM DESIGN & BUILD for both Canada & the US

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    Last edited: Dec 22, 2014
  2. johnfrwhipple

    johnfrwhipple BATHROOM DESIGN & BUILD for both Canada & the US

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  3. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    The steps have a slight back bevel on them...not much, but it doesn't take much.
     
  4. johnfrwhipple

    johnfrwhipple BATHROOM DESIGN & BUILD for both Canada & the US

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  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Cement based products don't compress much...it doesn't take much bevel on any surface in the mat to hold things down. And, the larger squares offer more 'air' space to allow for any expansion/contraction experienced between the tile and the subflooring. If you want to waterproof the assembly, say you want to use it in a shower, you'd need to cover it with Kerdi.
     
  6. eurob

    eurob master tile and stone installer

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    And all these years to say the tile has to be protected with an uncoupling membrane from the temperature swings and more from the heating wires ?!

    Talking about the hydronic heating.....even with the bekotec , it still requires the Ditra on top , before tile installation .
     
  7. johnfrwhipple

    johnfrwhipple BATHROOM DESIGN & BUILD for both Canada & the US

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    Last edited: Dec 22, 2014
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    The actual mass of the thinset is small, and close to the tile...the tile and thinset with the wire embedded will act together. When you have the heat underneath in the subfloor or worse, a slab, there can be a bigger differential. When you use Bekotec, you have a moderately thick mudbed screed of material, and the response and reaction times are quite different.

    The reason they didn't allow the heating mats or cables on top of regular Ditra was the unknown characteristics of each different heating cable or mat, and the possible risk of there being a void, or the accuracy of the heat control. It would be very difficult for the average person to get a reliable result and in the process might risk melting the membrane or burning out a wire. Only when you can control the materials selection and installation methods can you get things to work reliably. FWIW, the highest the thermostat will allow the actual tile to get is 82-degrees F, and there's a floor sensor buried in there near a wire to manage that. It is designed as a floor warming system, NOT a room heating system, like a typical hydronic, where there would be a higher BTU use and greater potential for differential stresses.
     
  9. eurob

    eurob master tile and stone installer

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    Wow.......the millions of heating cables installed with ditra on top ........and now this ( these ) ?!

    Makes me think 10 times before using them again :mad: ....and I was sure of the assembly until ...now ....damn . :mad: ....




    No John , just pics . But it is more to it than the dovetails . You need a megger to test and get a proper warranty before you install the tiles over it .
     
  10. johnfrwhipple

    johnfrwhipple BATHROOM DESIGN & BUILD for both Canada & the US

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    Last edited: Dec 22, 2014
  11. eurob

    eurob master tile and stone installer

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    Last edited: Apr 7, 2014
  12. Vegas_sparky

    Vegas_sparky Digital Billy

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    If its a high grade polyethylene is should be around 300°F. That should be well above the temperature of a heating cable encased in a cementatious product. Having the wire on top of the mat/just under the tile would produce a more even, and efficient heat transfer. Underneath the Ditra profile the voids from the lugs could add a negative insulative factor. Small yes, but not neccesarily predictable. That could affect the service life of the heating wire itself more than the perceived performance.
     
  13. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    The heating cables are conventionally either covered with SLC or thinset prior to the insulation of the uncoupling membrane...same as Ditra always has been prior to the introduction of Ditra Heat, which is slightly thicker, locks the cable into a known position, and is surrounded by thinset in any properly install. Ever read about cables or mats floating after an slc pour noticed the next day? Has it happened to you?

    FWIW, if you read the instructions for most of the heat mats, they recommend you check the insulation with a megger...Schluter, being conservative, does not want even that less than 1% chance the cable is defective or damaged after install before the tile, otherwise you'd have tear the floor up to fix. It comes down to being conservative and presenting an installation that is as close to certainly working. You can nick a conventional heating system's wire easily but it won't show up as a short. But, the Schluter system's thermostat contains a GFCI, so t doesn't take much of a fault to trip it...and the only way to fix that is tear up the floor. Is that something you want to do for a client, even if it is only once? Check it first, and you're golden. Same idea with supplying a second floor sensor...they do not fail often, but if you have a spare there, it's about a 5-minute fix with no tear-out. Which would you like to do? Again, conservative.

    Keep in mind that each of the 'towers' have a shaped notch to lock in the cable. Since you cannot install the cables closer than 3 towers apart, and at best you may be making a 90-degree turn around each post at the worst, you have a dovetailed notch to lock in the thinset, that notch will lock in both the cable, and when filled with thinset, lock the tile to the membrane. And, look at the size of those towers...lots of free air space for LOTS of differential movement between the tile/thinset and the substrate.

    Not BS, science.
     
    Last edited: Apr 7, 2014
  14. Vegas_sparky

    Vegas_sparky Digital Billy

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    A second thermister isn't a bad idea. I deal with them all day long. Even the best don't last indefinitely. I'm just sayin.

    I would think the stat/controller can also operate off of ambient air temp? Is the logic so that a failed floor temp sensor locks out operation to protect against the +82°F limit?
     
  15. eurob

    eurob master tile and stone installer

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    When you approve the uncoupling membrane on top of the wires , the word is negligible -- for more than a decade -- , not unpredictable .

    And how the service life of the heating wire is affected ? It is covered by the SLU before applying the uncoupling membrane .
     
  16. johnfrwhipple

    johnfrwhipple BATHROOM DESIGN & BUILD for both Canada & the US

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    Last edited: Dec 22, 2014
  17. Vegas_sparky

    Vegas_sparky Digital Billy

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    Coverage of the SLU can't be controlled(floating cables). That's unpredictable. Neither can coverage of thinset if its on top, unless you burn a layer in before you set. Those materials act as heats sinks for the wire, and their characteristics are engineered into the performance. Without those materials hot spots in the cable will develop, which affect there service life.
     
  18. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Nobody says what has been done before is wrong...it means that there is now a new way to do it that is faster, easier, and potentially more reliable. Continue to use an uncoupling membrane beneath the mat, and it will continue to work, and is totally supported by Schluter should you wish to do it that way.

    The thermostat has three sensing modes, one is just ambient room air temp. But, it still limits the floor temp to 82-degrees. Again, it is not a room heating system, it is a floor warming system. In some circumstances it might be able to suffice for heating, but you'd need an independent engineer to verify your room loads, just like should be done with any heating system.
     
  19. Vegas_sparky

    Vegas_sparky Digital Billy

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    John, I've been spending too much time doing temperature controls for things like jet fired power plants, and 20,000 HP central plants. LOL
     
  20. johnfrwhipple

    johnfrwhipple BATHROOM DESIGN & BUILD for both Canada & the US

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    Last edited: Dec 22, 2014
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