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Thread: Plywood thickness under tile

  1. #46
    DIY Member Justadrip's Avatar
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    This goes to show how easy it is to rile up Whipple. Too easy sometimes.

  2. #47
    ACO Shower Drain Sales johnfrwhipple's Avatar
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    Default Plywood thickness under tile - Double 5/8" plywood is best.

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    Last edited by johnfrwhipple; 03-16-2014 at 07:25 AM.


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  3. #48
    ACO Shower Drain Sales johnfrwhipple's Avatar
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    Post(s) removed by John Whipple
    Last edited by johnfrwhipple; 03-16-2014 at 07:25 AM.


    jfrwhipple@gmail.com - www-no-curb.com - 604 506 6792

    Always get construction advice double checked by your local city hall. Flood Test Every Shower - Every Time.

  4. #49
    Retired Defense Industry Engineer jadnashua's Avatar
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    The foam is the primary waterproofing layer of Kerdiboard, and when used in a wet situation, you treat the edges and any penetrations as if it were a seam, you use Kerdiband over them. John's worry about the backing of the orange layer is irrelevant if you follow instructions - it would be protected, and would not affect strength, as John alludes. Proper selection of the material for the task is important - thickness used depends on the application and whether it is applied to a surface where it needs to be self-supporting, or it is added like a surface and has a full thinset bond to it. In a non-load bearing wall, you should use 2" material and attach it to the cross section with their metal channel, and probably would want to use it also on the outer edge. When used as a countertop, it needs to be at least 1.5" thick, and can be attached to the top of say kitchen cabinets with KerdiFix and no further reinforcement is required. Penetrations for things like faucets require backing plates (typically a routed hole with a tile bonded in, then when you add your finish layer, that section has a load plate covered by the finished layer - i.e., two tiles thick, bonded into and onto the material).

    The stuff is quite useful, nice, flat, easily cut, carried, and you can do things with it that are difficult to impossible with wood construction for say tub decks, and many other things. Hardly the junk that John has called it. In the one picture of a failed installation John posted, one only needs to look at the data sheet for Kerdiboard http://www.schluter.com/media/KERDI-...v=201310190601 where the max temp is 70-degrees C. Guess what temp steam is? At sea-level, water boils at 100-degrees C. Easily out of the range of the material selected. If you also read the data sheet, it calls the exterior surfaces "a special reinforcement material on both sides and fleece webbing for effective anchoring in thin-set mortar." Nowhere in there does it call it waterproof, or the primary waterproofing material. IF you understand the properties of extruded polystyrene, you'd know for practical purposes, it is waterproof, the thinset compatible layer also being just aids the overall robustness of the material in both strength and performance. The Germans take things seriously...they rarely deliver junk (which John as called KerdiBoard many times).

    In the class at the factory in Plattsburg, NY, they specifically said you did not need to repair the surface layer if it was cut AS LONG AS IT DID NOT PENETRATE all the way through the material, since it was still waterproof. One would hope that the factory people understand how to use and install their product! This is the basis of saying the foam is the waterproof portion. Since that panel is not designed for things like a shower floor, or areas that are regularly submersed in water, there is little problem of saturating the back side of the material, and NO problem with it leaking through to the back side of the surface covering. FWIW, all of their linear shower sloped foam panels ARE covered with Kerdi fabric, because it is the PRIMARY waterproofing layer, even though the foam is as well.

    So, let's see how John twists these words...his ego just can't accept he could be wrong.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  5. #50
    ACO Shower Drain Sales johnfrwhipple's Avatar
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    Post(s) removed by John Whipple
    Last edited by johnfrwhipple; 03-16-2014 at 07:26 AM.


    jfrwhipple@gmail.com - www-no-curb.com - 604 506 6792

    Always get construction advice double checked by your local city hall. Flood Test Every Shower - Every Time.

  6. #51
    Retired Defense Industry Engineer jadnashua's Avatar
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    Humans are fallible. I've admitted making mistakes before, and will admit, the person I talked with was not the instructor. But I'll stand on the point that KerdiBoard is a useful, viable product and that John doesn't understand it or how it should be used (he may yet learn, but we'd probably never find out about it!). Slope is required where it could flow to a non-waterproof area (a curb in a shower is a good example), or saturate a component that could be damaged, or cause damage to areas beneath it when it sees constant or copious amounts of water. Neither of those two things can happen in a waterproof Kerdiboard niche, if it is installed properly. If the niche was made out of something like cbu, that would be a major issue as the material could be saturated, and create problems. The nature of thinset means there's very little material that can absorb moisture, and very little ever gets there beneath the tile and the grout, and when it does, it meets up with a waterproof assembly. The niche would tend to dry any moisture that did penetrate. Personally, in that instance, I'm not all that worried about slope...it would be easy to add to the applied tile, and then 99% would run off, and the 1% that was left would evaporate quickly. The goal of the slope is to prevent pooling...if you read the installation instructions, they suggest adding slope to the tile to prevent pooling when installing the optional shelf, but it's not a bad idea on the bottom edge, either. Much todo about nothing.

    FWIW, extruded polystyrene is a closed-cell foam, i.e., there is NO path for moisture through the material. Polystyrene material itself is also waterproof...so, you have a material that is itself waterproof that is covered by another waterproof layer on BOTH sides filled with closed cell bubbles created by the foaming process...damage the wet side, and you still have two significant layers of defense...the foam is waterproof. The surface, as stated in the data sheet, is added for strength and thinset compatibility. Another similar product, Wedi, is made up of the same material, but they use a special coating to provide thinset compatibility. And, if you look at their instructions, in making joints like the floor to walls, they tell you to create a rabbet joint, cutting into the material. If it wasn't waterproof on its own, that would not work. Similar, but not identical...when Schluter decided they wanted to produce a foam panel, they spent a lot of time and research coming up with one that had the properties they wanted, they did not want to clone someone else's product, and they didn't. There isn't a similar product out there with the properties of KerdiBoard (that I've been able to find, anyway), and therefore, people need an education on what it is and how to use it properly. That's why I went to the factory to take their class...get my info from people that know and understand the product and its nuances to application, and totally discount John's rant about it being junk.
    Last edited by jadnashua; 10-20-2013 at 02:54 PM.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  7. #52
    ACO Shower Drain Sales johnfrwhipple's Avatar
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    Default Important note - I'm not a pro ( no truer words spoken)

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    Last edited by johnfrwhipple; 03-16-2014 at 07:26 AM.


    jfrwhipple@gmail.com - www-no-curb.com - 604 506 6792

    Always get construction advice double checked by your local city hall. Flood Test Every Shower - Every Time.

  8. #53
    Retired Defense Industry Engineer jadnashua's Avatar
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    Per Schluter's instructions,
    "Where waterproofing is desired, the joints
    and corners of KERDI-BOARD in the
    area must be sealed with KERDI-BAND
    using unmodified thin-set mortar. The
    KERDI-BAND must overlap panel joints by
    at least 2" (50 mm)."
    "The instructions also say:
    Fastener penetrations may be sealed
    with KERDI-BAND using unmodified thinset
    mortar."
    What they don't say, is that they must be sealed if you want waterproofing. They did say that in the class. KerdiFix could be used, but cost-wise, the Band is often the better way. The Kerdi Shower manual is referenced in the KerdiBoard tech data sheet, and says to use that when building a shower which means any penetrations or seams need to be covered with Kerdiband with the requisite 2" overlap.

    So, putting the edge of the board in water shows nothing, since if it is installed per the instructions, those edges are covered if it needs to be waterproof.

    If you attend a Schluter training class, you learn not only the proper way to use their products, but pick up some tricks they've learned along the way, such as, a puncture that doesn't penetrate the entire board is still waterproof.

    Any assembly not build as directed is not a valid test, such as your edge in standing water...proves very little. If you've installed it properly, the entire backing to the outer covering will never get saturated, so your test on strength is kind of irrelevant. One can take a product and subject it to conditions it's not designed for, and try to make projections of how it will perform when installed correctly, but often, those will be incorrect.

    John still doesn't understand KerdiBoard.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  9. #54
    ACO Shower Drain Sales johnfrwhipple's Avatar
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    Post(s) removed by John Whipple
    Last edited by johnfrwhipple; 03-16-2014 at 07:26 AM.


    jfrwhipple@gmail.com - www-no-curb.com - 604 506 6792

    Always get construction advice double checked by your local city hall. Flood Test Every Shower - Every Time.

  10. #55
    Jack of all trades DonL's Avatar
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    This is getting good.


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  11. #56
    ACO Shower Drain Sales johnfrwhipple's Avatar
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    Post(s) removed by John Whipple
    Last edited by johnfrwhipple; 03-16-2014 at 07:26 AM.


    jfrwhipple@gmail.com - www-no-curb.com - 604 506 6792

    Always get construction advice double checked by your local city hall. Flood Test Every Shower - Every Time.

  12. #57
    Retired Defense Industry Engineer jadnashua's Avatar
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    Quote Originally Posted by johnfrwhipple View Post
    You write: "Seasonal changes may allow the wood to shrink after a dry hot summer...just depends. My unprofessional opinion." - I agree with both of these comments of yours some eight years ago. One wood dries and does shrink. It also checks and cracks. It is also total crap in a shower curb. This is why it's banned in Australia for shower curbs. This is why I use cement or bricks here in Vancouver. I also believe the later part. That your opinion in unprofessional. But I bet now eight years later you would say I like using Kerdi Curbs. Because your a Schluterville Graduate. OMG sad sad sad
    TCNA Handbook, 2012 edition, page 166 shows acceptable shower curb construction and says: "studs or cementious base for curbing" then shows a diagram.

    It depends on the situation, like I said. I would not use studs on an unknown slab (many older ones did not have vapor barriers under them, and one does not know if they were compromised during construction even if they did), since there could be moisture coming up through the slab into the wood. Seasonal changes (spring is often much damper than say the middle of the summer) may make that choice poor. But, on a wooden subfloor, properly constructed, and tested by the TCNA, wood is an acceptable and reliable curbing material...another example of John's always right, but it conflicts with the industry standards - do it his way, or you're a dupe or a shill.

    I would use pavers or brick to build a curb on a slab, or, if it met my needs and aesthetics, maybe a preformed one.

    But, cutting and assembling studs for a curb is both faster and less expensive and has been used in millions of showers. The only time it becomes an issue is if the shower was not built right and they get wet...John's argument would also apply to the structure - if the studs are going to create such a big problem in a shower wall, shouldn't you support your walls with cement columns or brick towers or metal studs? Why are they good there? Because, you waterproof or control the shower moisture properly!

    Using brick or pavers for all of your shower curbs is a waste of time and money....everything has to be evaluated which is why I keep saying risk/benefit/cost and some sanity need to be used when making a decision.

    Another example of John throwing stones. And, if you'll also notice, I'm not the one telling people to do nasty things...
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  13. #58
    ACO Shower Drain Sales johnfrwhipple's Avatar
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    Post(s) removed by John Whipple
    Last edited by johnfrwhipple; 03-16-2014 at 07:26 AM.


    jfrwhipple@gmail.com - www-no-curb.com - 604 506 6792

    Always get construction advice double checked by your local city hall. Flood Test Every Shower - Every Time.

  14. #59
    DIY Senior Member BobL43's Avatar
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    Quote Originally Posted by DonL View Post
    This is getting good.


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    Where is the Beer ?
    Now, now Don. It's not amusing to EVERYBODY! But it IS a pissing match. Too bad they are guys, otherwise I'd suggest a mud wrestling event.
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  15. #60
    Retired Defense Industry Engineer jadnashua's Avatar
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    Quote Originally Posted by johnfrwhipple View Post
    Didn't factory worker tell you that the Kerdi Board Niche's have a slope as well.

    If you handled a few of them and could not see a lack of pre-slope that is scary man. A Little Birdie told me you need glasses! LOL
    At a typical, industry standard 1/4" per foot, that two inch deep niche would have all of 1/24th of an inch difference back to front...not all that easy to see. You just like to poke at people...the installation instructions say you can slope your tile. THen, 99%+ is going to run off, and the rest will evaporate, and even if some does penetrate, the substrate is totally waterproof - there's not much room in the crystalline structure of the thinset for moisture to accumulate, and it really doesn't get there except maybe in places like a shower floor or where the showerhead hits...typically not right into your niche, except for maybe some splashes. Much talk about nothing. If this was made of some other substance slope or not would make a big difference, and, now that you've been told the bonding layer is waterproof (that's not in any of their documentation, it's only called a reinforcement layer and mortar bonding layer everywhere), you've got three layers of waterproofing. If you follow your installation method, you then add two more layers...just because you don't believe the things are waterproof in the first place. Extruded polystyrene is waterproof, and this is the core of Kerdiboard. Finding that the surface layers are also, is a bonus.

    FWIW, from a Dow Chemical data sheet (emphasis mine): "The closed cell structure of the XPS foam makes capillary water absorption impossible. But water vapour movement is possible through XPS foam." http://www.isover.com/Our-solutions/...ene-insulation sounds like waterproof to me.
    Last edited by jadnashua; 10-21-2013 at 06:30 PM.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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