Hardiebacker and Ply

Discussion in 'Tilers' Talk' started by C J ord, Aug 22, 2018.

  1. C J ord

    C J ord Member

    Hello,

    I have purchased some 12mm WBP ply to screw down on chipboard bathroom floor before laying 10mm porcelain tiles. However, following some research on the views of some on this forum I note that ply is not the best substrate for tiles.

    Can I screw the ply down then lay 6mm Hardiebacker on top of it.

    I realise that this would be raising the floor level which will mean shaving the top and bottom off the door and getting a longer soil pipe. If thats the way to do it.

    Please forgive the questions if it seems obvious to you guys but the fitter who started the job has left me in the lurch because hes got too much work on and in his words 'had to cancel a few jobs'.

    Thank you for any help you can offer.
     
  2. LEH

    LEH Member

    You can if you really want, but it's not needed and sounds like it will cause you trouble elsewhere.

    Here is an installation video:



    You will want to prime the chipboard before applying adhesive and the boards.
     
    C J ord likes this.
  3. Pollowick

    Pollowick Well-Known Member

    Rip up the chipboard and then get some Hardie Floor - 18 or 22mm and relay it.

    Chipboard + Ply + Backer is not the right way.
     
    C J ord likes this.
  4. LEH

    LEH Member

    I heard Hardiefloor was discontinued. But you can get 22mm nomoreply that would do the job as a structural cement board. Or GIFAfloor, but this is gypsum and so needs to be prepped carefully to avoid reaction with tile adhesive.
     
  5. Russel

    Russel New Member

    Heres another option!
    If you use the ply you need to prime and put Ditra matting ontop of it. If you install the ply make sure to use a mosaic notched trowel to apply (wettish) flexible tiling adhesive to the chipboard ( I mix pva/sbr with it aswell). Then screw down the ply thoroughly. This takes up any voids between the two layers and its the movement that contributes allot to tiles coming up. The floor becomes quite solid with the thickness of the two timber layers. Stick the Ditra down with acrylic glue or (tiling adhesive mixed with pva/sbr)
    Ditra takes up any laterall movement and your floor is nice and solid so has no deflective movement too.(assuming joists are good)

    I will personally come and replace this floor if it fails :)
     
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  6. Pollowick

    Pollowick Well-Known Member

    Last time I spoke with Hardie a few months back, it was available, although now it seems to be missing from their website!

    If it has been, then I would still suggest ripping up the chipboard and laying an appropriate layer of decent ply before topping with 6mm backer.

    I recently used 12mm backer for a floor - joists were are less than 300mm centres (nearer 250) and in between was the solid insulation for wet-underfloor heating so well supported.
     
    C J ord likes this.
  7. LEH

    LEH Member

    Another thought, although I suspect you’ve already bought your tiles - 12mm ply on top of your existing floor would make a perfect base for LVT. Quickstep Livyn is great, and would be way less work for you than what is required for tiling.
     
  8. C J ord

    C J ord Member

    Thank you for the help lads It really is appreciated.

    LEA, I have watched the vid cheerrs. Do you think I can put Hardie direct to floor without ply.

    Sorry lads I should have been clearer. Its a modern house with joists at 400 centres and 18mm OSB.

    Should I scrap the ply and put 12mm Hardie direct to OSB would this be as strong as 12mm ply.

    Cheers Pollowick I dont think I can get the existing floor up as its got stud partition walls on top of it. Do you think the idea of putting 12mm Hardi will be as strong.

    I like also like Russel idea of using ply and Ditra

    Sorry about questions lads but if I dont get it right the Mrs will be using the ply to build me a coffin.

    ATB

    Col
     
  9. LEH

    LEH Member

    It’s normal to overboard with hardie, no need for the ply layer in between, and this is going to mean the least amount of work for you, especially as it sounds like you’ve got a lot to do. Remember to prime the osb first then follow the manufacturer instructions. Make sure the osb is securely fastened to the joists, add screws anywhere that seems to have movement.
     
  10. C J ord

    C J ord Member

    Thank you for the help LEH it really is appreciated the fitter has left me right in the lurch.

    Will 12mm Hardi or no more nails be better than 6mm. Sorry about the questions bud but I am struggling with these modern materials. Its a long time since I have done this but ive been left with no option.

    ATB

    Col
     
  11. LEH

    LEH Member

    6mm is recommended for floors. Nothing to stop you using 12, but not needed, usually people are trying to avoid build up of the floor height.
     
  12. C J ord

    C J ord Member

    Thank You

    ATB

    Col
     
  13. longboat

    longboat Well-Known Member

    You've got the plywood, screw it down with decent screws (reisser/Spax etc) at 150 spacings and prime the floor with, SBR, or tile primer before laying the tiles with a flexible adhesive and grout.
    Make sure you have full coverage on the tiles and back butter if needed. Use grout that's suitable for all applications and you've got a lovely tiled floor that will last for for years to come.

    This 'hardibacker', ditra matting and associated bumph, is nothing more than corporate sales speak where the domestic market is concerned.

    Totally unnecessary expense.
     
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  14. Russel

    Russel New Member

    I have seen so many floors fail with just ply. And done many floors with Ditra and NEVER had a failure on those floors.
    Ditra works, this video makes its function clearer.
     
  15. LEH

    LEH Member

    As I think I posted elsewhere recently, tiling onto ply is no longer recommended by the relevant British standards. Due to poor quality of materials, big tiles etc. Any timber surface moves too much, especially in a damp environment like a bathroom. Yes people used to tile on to ply all the time but things have moved on and there are better options these days. Why risk it.
     
  16. C J ord

    C J ord Member

    Thank you for helping I do appreciate it.

    ATB

    Col
     
  17. C J ord

    C J ord Member

    Thank you all for helping

    I really am in the **** as the wife has got no bathroom through the fitter letting us down. He was going to put ply down which is why I already have it stored in my living room but when he deserted us and I looked for advice on this forum I noticed there was other ways of doing it and just want to get it right.
     
  18. longboat

    longboat Well-Known Member

    I've seen a few floors that have failed when applied to ply, but on closer inspection it's almost certainly due to incorrect instalation methods. Non flexible adhesive being used or stuff that's past its shelf life. Failure to prime the ply or lack of back-buttering if needed. And then of course there's the bodgers favourite, the dot and dab method.

    After what must be hundreds of flooring jobs completed, I've never had any comebacks and many of these floors I can see 5, 10, 15 years later when I'm called to do other work in the property and they look good as new.

    However, I can see a legitimate market for the matting on new builds where the structure is open to the elements, so to speak, without heating or time to settle.
    In an established dwelling though, there really isn't any need. As I said, it's an unnecessary expense.
     
    Jord86 likes this.
  19. C J ord

    C J ord Member

    Thanks for that longboat.
    I did buy the best ply I could it was WBP, structural hardwood ply.
    I really need to crack on as the wife has got no bathroom.

    .
     
  20. Ian Bolton

    Ian Bolton New Member

    Ive Done 2 bathroom floors used 18mm structural hardwood ply heavily screwed on to the floor boards, I used flexible tile adhesive and grout, as everyone seemed to recommend at the time, within 2 years the tiles started coming away in the areas of heaviest use. Everything flexes apart from the tile so the adhesive eventually comes away from the tile, then the grout starts to crack. Honestly dont use ply if I was to do it again I would use hardiebacker as it wont flex, or look at the ditra that longboat recommends. It may add time and expense to the job but if it stops the tile adhesive failing and you dont get to hear that dull thud every time you step on a tile because its loose then its worth it
     
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