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Thread: Plywood thickness under tile

  1. #61
    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.

  2. #62
    Retired Defense Industry Engineer jadnashua's Avatar
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    Just to be clear, while John may have 'quit' www.johnbridge.com (which I find hard to believe since he loves to post things), they banned him, and he cannot log back in. As a result of whatever ticked him off, as a result, he throws darts anytime he can. There is a huge cadre of working, award-winning tile guys AND women over there, glad to help, regardless of what John says. For years, the shower and bathtub section of Terry's site was related to plumbing questions related to those rooms, not tiling, which John wants to be his personal domain...he hates any competition. Terry approved of people recommending that site for tile expertise, regardless of what John touts, and the people over there would suggest people there come over here to get expert answers to their plumbing questions, a good working relationship - go where the expertS are (i.e., more than one). This is the reason I link people to that site, to get a clearer choice of industry approved methods, not those that John decides is the only way to do things. As opposed to what John alludes, there are lots of people over there that can help you build nearly any type of shower, and the information in their library covers most of them, and there are people that have there preferences for pretty much all of them, so lots of varied experience. The TCNA handbook is several hundred pages long, describing the approved ways to build things or cover things with tile...each one has it's own cost/risk/benefit. John would have you do it his way, and the industry and experience of millions of installs over many years, that there is more than one way to do things and not have your world fail. The skills required to accomplish the task in any approved technique needs to be weighted according the your cost/benefit/risk tolerance and skill level. The task is detailed, but not hard, and there is more than one place to get information, and there is more than one right answer...John just doesn't think that way.

    I freely admit I don't tile every day, but have some experience in more than one area. I have had some training, and have worked in highly technical areas most of my adult life where you need to evaluate the cost/benefit/risk of any decision. Over 30-years of that hones some ability to evaluate information and make good decisions, and to spot where someone is full of their own importance.

    I'm sure John will make some snide remark. Just take it in context with his ego, his track record on other websites, and go from there.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #63
    Retired Defense Industry Engineer jadnashua's Avatar
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    With regards to creep, which is the deflection changes over time to a loaded structural member, some experiments were performed and documented in a doctoral thesis http://scholar.lib.vt.edu/theses/pub...097520/etd.pdf . Take a look at Figure 4.51, and notice how the deflection changes over time (creep) with the same load. The creep here was charted at about the typical design dead load. Later diagrams show other structures with various loads, but he creep clearly shows the structure continuing to bend over time up to approximately 150% of that in the first few months.

    Excessively loading the structure means that you push the curve, and since the wood is only so elastic, the creep can end up larger as the structure is actually damaged, verses just flowing.

    Feel free to read the whole thing (it's kind of boring, but if you understand at least some parts), it's easy to see that a load on a structure does not produce a finite, inflexible, static change...it creeps (increases over time). When you're dealing with an inflexible surface like tile, if you push the limits, over time, you may very well see failures exhibited by cracked grout, broken tile, and possible delamination. One other thing you'll find from the study, is that there hasn't been a lot of study of this effect, and this was an effort to try to find a mathematical model that could be used by architects and structural engineers to analyze and evaluate structures for long-term reliability.

    Simplistic advice (the math can get really messy), avoid overloading your structure, weight is not your friend, deflection is real, and what you see in the load tables does NOT account for creep. There are consequences, regardless of what John Whipple thinks, of long-term creep to a structure, especially when you go over and above what the industry recommends. Risk/benefit/costs, you decide your tolerance, and don't shoot the messenger (please)!
    Last edited by jadnashua; 10-21-2013 at 10:39 PM.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  4. #64
    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 07:27 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.

  5. #65
    Jack of all trades DonL's Avatar
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    OK. I need to ask.

    John, why do you find the need to Bash Jim ? On this forum ?

    I think you may need to move on. When were personal attacks allowed ?


    I have 6 inch's on you for a good pissing match.
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  6. #66
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    Post(s) removed by John Whipple
    Last edited by johnfrwhipple; 03-16-2014 at 07:27 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.

  7. #67
    Retired Defense Industry Engineer jadnashua's Avatar
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    I find it interesting that two Ph.Ds one of which is a well respected professor at a good technical college say the same thing, and John totally disregards it - maybe he couldn't understand it, therefore it doesn't exist or must be wrong. Long-term creep in wooden structure is a fact. The experiments performed as part of that dissertation are repeatable, and had multiple samples (unlike most of John's tests, where he came to a conclusion with one sample). Adding extra weight not called for in the industry guidelines adds to the problem. The load tables are derived without long-term creep accounted for, and they are based on a specific load (nominally 10#/sqft dead load). When you increase the dead load above those limits, your deflection increases and the margin you thought you had starts to evaporate, and the long-term creep rate could be a bigger factor. So, there's a cost/benefit/risk...adding extra stuff above and beyond what is required has a real risk. All I did was point that out, and then provided two independent, peer reviewed references that backed that up. Adding stuff for a good engineering reason certainly makes sense, but doing it arbitrarily, without understanding the risks, has its perils. You don't add stuff to an airplane to make it stronger unless it's needed, the costs aren't worth it. Same thing is true anywhere...are you willing to afford the costs and risks. I also find it funny that John disregards the TCNA guidelines on what has been tested, evaluated, and verified, as viable methods to achieve an end (take the curb issue he brought up). His way is the only way, anyone else's is crap, and unreliable. Same thing is true with Schluter and the use of Kerdi...as listed in the USA and Canada installation manuals (he does live here!), it meets all of the requirements for a reliable shower, but John feels he must augment that, calling it inadequate. This adds cost with no real benefit except to his bottom line (more labor, more time, more money) - certainly not to the customer. If he did it right per their tested, verified methods, it would work, and be warrantied by the factory. Maybe he doesn't trust his workmanship, and therefore needs those extra steps to guarantee it.

    John hates, the www.johnbridge.com website, and anyone associated with it. Why he 'quit', when he had a forum to express his ideas, I don't know the full details, but he IS permanently banned from ever logging back in (at least they feel there's a good reason). And one other site had enough of his rants and character assassinations to ban him as well. Why I continue to point people over there if they have a question on tiling things, is that they have NUMEROUS working pros, with lots of real-life experience to offer opinions, here, we currently have one, very inflexible, opinionated one.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  8. #68
    ACO Shower Drain Sales johnfrwhipple's Avatar
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    Default Subfloor Prep for older Vancouver Homes.

    Post(s) removed by John Whipple
    Last edited by johnfrwhipple; 03-16-2014 at 07:27 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.

  9. #69
    Retired Defense Industry Engineer jadnashua's Avatar
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    John still doesn't understand my points...

    He thinks that I'm challenging his tile layout, bathroom layout, and execution of setting of the tile. All appear impressive from the pictures he posts and what most of the people look at in the end...

    But, it's how he addresses the underlying structure and uses the materials underneath that are at issue. Why, for example, on a KerdiBoard niche that has three layers of waterproofing (front/back layer and the foam) does he feel it is imperative to then add two layers of Ardex stuff? Why does he require adding it to Kerdi? Why does he feel he needs to trash a product that has passed all unbiased independent tests that says it works? Why does he say that only things he cherry-picks in the TCNA handbook are the only way to do things? Why does he say that he needs to add extra material above and beyond what the industry that has proven it works as the only acceptable way to perform a job?

    In his mind, he is always right, his way is the only way, and he slams anyone that says anything that calls him on it. The testing agencies do what they say, the manufacturers have a vested interest in staying in business with satisfied customers, why would they promote a method that didn't work?

    Why are we to believe in light of all this that John's way is the best and only way to perform the task?

    I try to point out where the industry says that's excessive, and it works just fine without those extra layers. They add costs, both in materials, and labor, and what John doesn't seem to want to accept, weight that can have some serious long-term effects.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  10. #70
    ACO Shower Drain Sales johnfrwhipple's Avatar
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    Default Why are we to believe in light of all this that John's way is the best?

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    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.

  11. #71
    Retired Defense Industry Engineer jadnashua's Avatar
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    Here's what the TCNA has to say about it...https://www.tcnatile.com/faqs/31-efflorescence.html
    "Except in the rarest of cases, efflorescence does not occur from the small
    amount of minerals in water used to wash a floor. Nor when tile is installed
    with thinset (tile cement) are there enough soluble salts in the thinset to
    cause efflorescence.

    Occasionally, when tile is installed over a thick mortar bed, the mortar
    could provide a sufficient amount of soluble salts to cause efflorescence but
    only if moisture is regularly passing through the mortar bed.
    "

    You do not have a thick mortar bed over Kerdi, nor Ditra.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  12. #72
    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 07:27 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.

  13. #73
    ACO Shower Drain Sales johnfrwhipple's Avatar
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    Default efflorescence in a Kerdi Shower

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    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. #74
    Retired Defense Industry Engineer jadnashua's Avatar
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    Without knowing what type of grout was used, or testing the material, this is not definitive proof of much.

    The TCNA has inputs from all over the USA and Canada and representation from most manufacturers. I take their advice with more than a grain of salt. They actually test things and have the ability to analyze the results rather than guessing what happened.

    I'm hoping you didn't build that shower, if you did, it's not a particularly good example of good skill! Pretty amateur cuts, and edges and alignments. So, we're back to what John says, verses what the TCNA says.
    Last edited by jadnashua; 10-24-2013 at 12:44 PM.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  15. #75
    ACO Shower Drain Sales johnfrwhipple's Avatar
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    Default How to pick a Shower Niche that's Not stuck in a rut

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    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.

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