Installing heated floor on plywood base

Discussion in 'Shower & Bathtub Forum & Blog' started by rdavison39, Jan 18, 2011.

  1. rdavison39

    rdavison39 New Member

    Jan 5, 2011
    Toronto, ON Canada
    I may have this in the wrong forum but i didn't see a form on tiling.

    I'm about to install the Suntouch heated floor system - essentially heated wire embedded in a mesh. The floor i'm installing it on is 5/8" plywood. Normallyl before i would tile the floor i would staple down 'chicken wire' and then lay down thinset. Question i have is this......

    is it okay to just staple the heated pad into the plywood and apply thinset to it....or should i do this in 2 layers. That is, first layer being the chicken wire covered in thinset - let it dry - then laydown heated and cover in thinset again.....

    I did see some "1 step" video where they just put the polymer cement on top of the wires and plywood and then layed the tiles on top.

    Any help would be appreciated
  2. geniescience

    geniescience Homeowner

    Nov 27, 2005
    humid summers hot, humid winters cold
    no chicken wire. By the way, nobody will guarantee the result except you. Because chicken wire is not an "approved" method. And skipping the chicken wise and using the mat as like kinda the same thing is like kinda the same situation. Sort of like that.

    In some internet forums, people won't say anything except "here is the approved method". Anything else leads to never ending squabbles. Very few people have been in your situation. Choosing between chicken wire or mat or both. There are other "membranes" and other ways of getting thinset to stick to plywood, that are warranteed by the latex manufacturer.
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  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    First off, 5/8" plywood is the absolute minimum recommeneded for tile installation (and it must be in perfect condition and properly installed), and all approved methods require a membrane or cbu as a decoupling method on top of it. Then, if your builder only put 5/8" ply, the joist structure may be minimum, too, and may not support tile. To work, long-term, tile needs a floor structure with at least an L/360 rating for deflection. You determine this , not by the room size, but by the length of the unsupported joists underneath the floor (i.e., say from a support wall, foundation, or beam). This is determined by the spacing, depth, width and length of the joist along with the species type (some woods are stronger than others).

    The chicken wire and thinset is referred to as a 'Jersey mud job', and has been proven to not meet any industry standards. Failure is not certain, but common with this type of installation. It can take anywhere from weeks to years to occur, but frequently does. Use any one of the approved methods, and you should expect it to last as long as you'd like it to...IOW, until you get tired of it and want to remodel, not because the tile or grout cracks and tile pop loose.

    For some guidance on tiling issues, check out
  5. johnfrwhipple

    johnfrwhipple BATHROOM DESIGN & BUILD for both Canada & the US

    Jul 20, 2009
    Design Work World Wide: Bathrooms Vancouver Area
    North Vancouver, BC
    Hi Ron. You ask a great question and one that can be answered in many different ways.

    First off there is no real way of telling you anything until we know way more about your floors structure and tile choice. Have you done any work like this before? Is this your home? Is it in a rental? What size tile are you laying? What is the tile made from? How big is the room? Do you know if the floor joist where knotched or over drilled?...

    Just a few questions to get the ball rolling.

    I have done many installs and I have used "Chicken Wire" myself in the past. Some guys tie the heating wire to rebar before they poor. It all depends on your local inspector and what he wants to see. Some inspectors are by the book and other's are more practical.

    Can you upload some pictures. Your tile choice. Drawings. Sketches... Lots of home work but if your you really want to know the right answers there is no other way to give it to you unless you do the leg work.

    I've installed thousands of feet of this heating wire. I've had it inspected. I can help you but unless we know the job we are just talking "Smack"...

    I would stay here for advice. There not to friendly to Canadians on John Bridge's site in my opinion. Lots of old Canadian jokes.... "EH". If you get what I'm saying. That and most of the heavy posters are retired...

    I'm on the West Coast - don't hold that against me.... :)

    I'll still help you - even if your from Toronto... ;)

    John Whipple
    Linear Shower Drains.

    By Any Design Ltd.

  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    IF you floor structure is sufficient, embedding the heating mat in SLC will give you a nice flat surface to tile to. Nearly all SLC manufacturers require lath (not chicken wire!) under their product. Latticrete (I think still) makes a plastic lath material that would work well with a heat mat to then tie the mat to prior to pouring the slc. Also, over a plywood base, most SLC specs call for the stuff to be at least 1/2" above the top of the highest point. This may make the floor taller than you want, but if done properly makes a great surface to tile onto. I don't know what John's problem with John Bridge's website is, but I've found it to be quite helpful. Whether someone has retired from the industry or is still actively installing tile...experience is experience, and they have lots of people there that can help. you don't have to take their advice, but it is (generally) backed up by solid research. They abide by the Tile Council of North America's research and recommendations, which is a recognized testing agency on all things tile. If you want, you can get a copy of that document, and view all of the tested and approved methods of installing tile....chicken wire is not among them (except maybe when making a mudded wall or floor, and then, you are using mud pack, not a thin layer of thinset).
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