new Uncoupling Mat

Discussion in 'Shower & Bathtub Forum & Blog' started by johnfrwhipple, Apr 9, 2013.

  1. johnfrwhipple

    johnfrwhipple BATHROOM DESIGN & BUILD for both Canada & the US

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    Sorry folks. I removed much of this discussion since it refrenced Ditra and I have quit using and talking about Schluter's products.
     
    Last edited by a moderator: Nov 26, 2016
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    With Ditra, the anchor to the membrane is more the dovetail, and at least on that top surface, there is no fleece. The dovetails lock the tile in. The reason you can't use tile smaller than 2x2" on Ditra is those plastic dividers which are only there to create the dovetail pillars. The industry standard for bond strength of the fleece is a MINIMUM of 50#/sqin. Both Ditra and Kerdi typically test out at 150% of the minimum standard. It doesn't sound like this new product will meet that standard, and you are relying entirely on the mesh, both top and bottom to hold things in place...doesn't sound very reliable.
     
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  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    WIth that thick of a mesh, it may be enough to allow moisture to wick along the surface. ANd, as you mentioned, it would be very difficult to embed it entirely in the thinset, leading to potential soft surface, susceptible to deflection of the fleece. I'd have to see and try it, but from the pictures, it doesn't impress me.
     
  5. suceress

    suceress Member

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    I really love that you are into testing out new products. I wonder if the sample you were given was some sort of dud. But I imagine you thought of that already.

    What exactly is the purpose of these mats? I get that you put tile over them, but I don't know anything more about them than that. I know you mentioned Holmes on Homes as advertising products, but one thing I did note on that program was that they would put down some sort of mat underneath the tiles to sort of buffer it so it would be more forgiving if the subfloor wasn't perfect. At least that was my understanding.

    I wonder how these would work with in-floor heating... Would the heating things go on top of it? Or would something like this just not be used.

    I'm interested in seeing what you find with your Mad Lab testing.
     
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    http://www.schluter.com/7214.htm pretty much tells and shows the intent of a good underlayment. The membranes are typically thin enough that they do not affect heat transfer when using in-floor heating systems.
     
  7. suceress

    suceress Member

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    Thanks, jadnashua! I'm loading the video now.

    I'm no expert, but I would think that the thick fleece on the spiderweb II would not conduct the heat very well. Am I wrong on this? It looks like there is enough air in the fleece that it might work as sort of insulation-- unless it just gets very saturated with thinset/adhesive to the point that it wouldn't interfere.

    Its something to consider in testing perhaps?

    Edit: Finished watching the video. I had an "ohhhh! That's how it's done!" moment when I saw how they did the tiles that went a few inches up the wall. I also found myself picturing just how I would end up getting stuff messed up and askew if I were to try it myself. Anything with adhesive and I always end up getting it crooked. LOL.

    That was very informative.
     
    Last edited: Apr 9, 2013
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    If the mesh gets embedded well into the thinset, it becomes a non-issue. I'm not sure you'd be able to do that with the new SpiderwebII.
     
  9. suceress

    suceress Member

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    I'd love to see how things turn out.

    Not to sound like a sycophant, but I really do think its awesome that you go to such lengths to test the products. I think it really is cool and it helps to have a better understanding of how the products work, their limitations, etc. Too bad there is no "like" button on this forum.
     
  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    The strength test is after full cure...shortchange that, and you risk failure. The industry standard is 50#/sqin for this type of material. Independent tests have shown the Schluter products to achieve at least 75#. Do it before full cure, I do not know the results.
     
  11. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    It's rated at the nominal 28-days. It's a shear measurement (parallel to the face), not a hanging measurement (perpendicular to the face), and this assumes a monolithic surface (i.e., grouted). You'd have to look up the specifics of the test. Schluter discusses it in their installation manual, and that may also list the test procedure. Need apples-apples if you want to run the test. Anything over 50#psi meets the industry code for this type of material. When Schluter had the test run, the testing agency came up with 75#psi as the fail point - 50% above the minimum.
     
  12. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    No idea what kind of strength you'd have with a pull test. The vast majority of stress on tile is in shear, either from bending or if on a vertical surface, just from the weight. As noted, at least as I remember it, the 50psi industry rating is for shear, not pull. I'm not sure I've seen a pull test requirement.
     
  13. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    On a wall would be more in line with my understanding of the test procedure.
     
  14. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    I think the grout simulates a full wall install better, since it ties the stuff together. Makes it harder for the membrane to shear off, since it's sharing the load across a larger area. But, I have not read the details of the actual test procedure, so may be misinterpreting it.
     
  15. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    The industry tests are after 28-days, the standard for cement based products. After the first week, it has most of the strength. But, also consider that cement continues to gain strength for years, the 28-days was a calculated compromise based on typical construction timelines representing 'typical' strength.
     
  16. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    What's the bonded surface area of the brick? As has been said, a membrane should hold at least 50#/sqin. From a practical viewpoint, I think you've proven you're not likely to strip a tile off the wall easily once the mortar has cured some, at least for Ditra, you've tested.
     
  17. nukeman

    nukeman Nuclear Engineer

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    It looks like you are well under 50 psi for shear. At ~1500lb, this would only be 30 in^2 to get 50 psi shear. I suspect that you are closer to 25 psi based on those numbers.

    However, are you sure about the weight per can? You are saying 150lb per can. At 150 lb, this is only about 18 U.S. gallons. Those cans look to be double that. They are probably at least 32 gallon cans and they may even be 44 gallon cans. So, I think you are really looking at more like 250lb/can (could be near 350lb/can if they are 44 gallon cans).


    If that brick is say 6x12, your failure could be around 3600lb (assuming 50 psi shear). 50 psi is probably in the ballpark since it hasn't had the 28 day cure. It will have most of its strengh after 1 week, but will continue to get better with a longer cure. Your test may also be a bit lower than the actual tested value if your testing surface wasn't perfectly plumb. This could induce a twisting force (instead of pure shear) and say pull the top of the brick away from the surface while also pulling downward.

    This goes to show you how well a good thinset will bond to tile. Even a cheap unmodified thinset could support hanging a car off say a 12x12 tile. I like a good modified thinset more many reasons, but as you can see, the additional strength of the modified thinset isn't really needed. If you had enough shear to really need modified during an actual install, you would probably pull down the house before you actually sheared all the tiles off. :)
     
  18. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Without a copy of the industry test procedure, it's easy to not have the same conditions, and the test results differ. In the tests done, it appears that the membrane tore at the top, which then peeled the rest off. Not being there, it's hard to say. I guess, though, that the bottom line is that properly installed, you should not worry about the tile coming loose on its own! If the industry test called for the tile to be grouted, this would also tie multiple tile together, increasing the overall effort required to pull any one tile out. Also, at least with the Ditra, the thinset doesn't really stick to the top side...it is locked into the wedge shaped pockets. So, the effort to pull it up is more of a function of distorting those pockets to get that wider base popped out of them, than the membrane breaking loose from the subflooring.
     
    Last edited: May 3, 2013
  19. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Once the bond between the fleece and the membrane breaks, the only thing left is the plastic, and that, while tough, will tear. I agree, as long as you are consistent in how you run these experiments, the relative differences are accurate but may not match the industry standard test.
     
  20. chefwong

    chefwong Member

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    KEWL Testing you got there.

    I've yet to read the thread in it's entirety.....but give me the cliff notes version on the shear strength testing.
    Seems mighty strong nevertheless .....for a application that is horizontal
     
  21. chefwong

    chefwong Member

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    Heh. I mean what was the point of the shear test - bearing the stuff we are talking about is generally on a horizontal surface...

    Nevertheless, love the LAB WORK !
     
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