Tiles not bonding to ply floor

Discussion in 'Tilers' Talk' started by dcox, May 17, 2022.

  1. dcox

    dcox Screwfix Select

    I finished a bathroom last week and the customer asked me to come back to repair a bit of grout that had become loose between the floor tiles. I had a look and could feel slight movement between the tiles. Went back today to lift tiles to see what’s going on and the adhesive just hasn’t bonded to the ply.

    I laid 12mm ply over good, well screwed floorboards sealed with a couple of coats of Mapei Primer G, combed mapei slow set flex adhesive on to the tiles then laid. I would usually apply adhesive to the ply but I’d marked out guide lines that I needed to see.

    I’m going to start redoing it tomorrow. How can I avoid more problems?
     

    Attached Files:

  2. longboat

    longboat Screwfix Select

    If you really need to apply the adhesive to the tiles rather than the floor then spread a thin coat of adhesive to the ply too.
    When I need to follow a marked guide line I apply the adhesive to the floor just shy of the mark so it's still visible.
    Also, looking at the pic's perhaps the adhesive was mixed a little dry.
     
    JimTiler likes this.
  3. dcox

    dcox Screwfix Select

    Thanks for that. It’s a new adhesive to me - usually use Topps - and it thickened up a few minutes after the mixing so you’re right about it possibly being a bit dry.
     
  4. terrymac

    terrymac Screwfix Select

    Never used mapei stuff ,are you sure it's not either out of date ,or not suitable for ply/ porcelain tile ?
    As above ,it doesn't look as though it was very fluid when applied ,and dry looking.
    Adhesive is best applied to the floor and a deep notched trowel used.The fact that the " tram lines" are still Visible is indicative that the tiles have not been twisted/ pressed down very firmly when laid. Butterring the back of the tile isn't a bad idea either.
     
    dcox likes this.
  5. dcox

    dcox Screwfix Select

    Thanks, Terry.
     
  6. stevie22

    stevie22 Screwfix Select

    Just a thought, but has it possibly been walked on prematurely?
     
  7. DIYDave.

    DIYDave. Screwfix Select

    I’m wondering if the issue is down to the choice of primer used - Mapei G over plywood

    Think a latex primer is recommended for wood, either a tile brand, Bal Bond as an example, or good old SBR diluted 1-3 water

    Primer G says it a ‘synthetic resin primer’ - although in all honesty, I have no idea what that means but a quick look at the data sheet doesn’t mention using over wood as prep prior to tiling

    Maybe call Mapei technical line for info

    Good luck
     
    JimTiler likes this.
  8. JimTiler

    JimTiler Active Member

    Above is correct, wrong primer used.

    Primer G is mainly used when sealing gypsum anhydrite screeds.
     
  9. JimTiler

    JimTiler Active Member

    And to be honest there are much better options than ply for tiling on today.
    6mm Hardie is probably the best, imho.
     
  10. DIYDave.

    DIYDave. Screwfix Select

    Thanks for confirming my suspicions Jim, I do ‘stick my neck out’ from time to time on this forum and as a mere diyer, I occasionally ruffle a few feathers !!

    Will add that I take no pleasure in my reply as it’s caused a problem for the OP, but at least we now know where and what the likely issue is

    So, if the plywood is staying, OSB over the Primer G ? Or not ?
     
    JimTiler likes this.
  11. dcox

    dcox Screwfix Select

    Good to know. Can I apply a more suitable primer over the top or am I beyond that option now?
     
  12. JimTiler

    JimTiler Active Member

    Best resolve for me would be take it back to floorboards and fix 6mm Hardie and then tile.
     
  13. dcox

    dcox Screwfix Select

    [QUOTE="

    So, if the plywood is staying, OSB over the Primer G ? Or not ?[/QUOTE]

    OSB? Do you mean SBR?
     
  14. dcox

    dcox Screwfix Select

    …and the second best resolve? I’ll try hardibacker on the next bathroom but would be a challenge to lift and replace the ply here because of everything else that is now fitted in the bathroom.
     
  15. JimTiler

    JimTiler Active Member

    Overboard the ply...

    Problem is if you just SBR the ply will you still get the adhesive to bond due to the Primer G residues.

    If I was in your situation, and we have all been there, I would start over.
     
  16. dcox

    dcox Screwfix Select

    I used the same primer on new plaster on the walls with no problems, so I’m struggling to understand quite how the tile adhesive wouldn’t bond to it on the floor. I could understand the primer not ‘taking’ to the ply, but this doesn’t seem to be the issue.

    I think I’ll take a gamble and redo with the Topps adhesive that I’m more used to but keep the substrate as it is. I haven’t lifted the small cuts around the edge of the room as they seem to have bonded and some are quite complicated cuts around pipes etc, so would have to redo those as well if I was going to overboard. It’s only about 8’ x 6’ so not the end of the world if I do need to do it *again*. But I will take heed of the good advice for future floors. Thanks everyone.
     
  17. dcox

    dcox Screwfix Select

    From the primer label: “…for porous and gypsum-based substrates.” I think I’d class ply as porous. I’m not saying there are aren’t more suitable primers but I can see why this was recommended.
     

    Attached Files:

  18. DIYDave.

    DIYDave. Screwfix Select

    OSB? Do you mean SBR?[/QUOTE]

    Opps, yes, SBR I did mean to type, and more a question to Jim Tiler rather than me saying ‘yeah, go ahead and use SBR’

    Too many acronyms and I was typing PDQ !
     
  19. DIYDave.

    DIYDave. Screwfix Select

    I’m no chemist and purely diy but recon it’s just down to different chemical compositions of primers that make one more suitable for a particular (or a range of substrates) than another

    Primer G does mention ‘porous’ but doesn’t specifically mention timber as a suitable background, more plaster based

    Bal Bond does however mention timber as a suitable surface to prime, along with several others so perhaps a more flexible product in its uses

    The Keraflex Standard Set adhesive (if that’s the one you’ve used) is suitable for porcelain tiles (if that’s what the tiles are ?) and check it’s in date

    If all answers yes, then running out of other viable causes, other than the choice of primer

    I’m of the understanding that Mapei products are highly regarded within ‘the trade’ so can’t blame it on not using your usual from Tops !

    Hope you get it sorted with as least hassle as possible mate
     
  20. dcox

    dcox Screwfix Select

    Thanks. I reckon my mix was just too dry - it behaved differently to what I’m used to. I’ll stick to my usual brand and hopefully all will be good. My local Topps branch closed hence the decision to use something else.
     

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