Tiling onto a mist coat- avoid?

Discussion in 'Tilers' Talk' started by LJdiy, Nov 9, 2018 at 8:02 PM.

  1. LJdiy

    LJdiy New Member

    Hi all, I've lurked on this forum and got lots of tips but never posted before.

    My Dad and I are redoing by bathroom and learning as we go along. All the plumbing is now done so we had the whole room replastered (green board).

    I mist coated the whole room and now I'm worried that was a mistake as I've now read that you shouldn't tile onto paint.

    Does it help that it's only a very thin coat?! Or do I need to remove it now?

    Should I prime the wall?

    I'll be using Mapei Keraflex S1 with 150mm square tiles.

    Thanks in advance for your advice. Laura.
     
  2. chippie244

    chippie244 Well-Known Member

  3. Aura noire

    Aura noire New Member

    Yep the wrong thing to do!
     
  4. Aura noire

    Aura noire New Member

    Got to get the paint off now.
     
  5. Astramax

    Astramax Well-Known Member

    Two differing replies!
    As it is only a mist coat and probably only a thin one at that I would also crack on, to be honest I have seen and also tiled areas myself that are far more disastrous than a thin mist coat without any negative effect!
     
    longboat likes this.
  6. Aura noire

    Aura noire New Member

    In what way do you mean a negative effect?
     
  7. chippie244

    chippie244 Well-Known Member

  8. Aura noire

    Aura noire New Member

    No, new member, been tiling 18 years.

    Tiling on paint if any kind is only going to adhere as well as the paint is to the wall.

    What are the tiles? Ceramic or Porcelian?

    Remember plaster skimmed walls can only take 20kg sqm, this applies to skimmed plasterboard also.
    And this weight also includes the tile adhesive and grout, that’s 4kg sqm.
     
  9. jimoz

    jimoz Member

    Previous tiler I used always used to scratch up the surface beforehand if painted. I now do the same if gripfilling and nailing anything to plaster. Tiler on this job atm primes all walls. Don't know what with but it's obviously for that purpose.
     
  10. chippie244

    chippie244 Well-Known Member

    The point of a mist coat is that it soaks into the pb rather than sits on the surface.
    Sorry about the troll accusation, one appears every night about this time and picks fights.:oops:
     
  11. LJdiy

    LJdiy New Member

    Thanks all for the responses so far.
    Chippie- I was thinking the same about the mist coat mostly being absorbed into the plaster. 2/3 of the room is going to be painted so I was doing my mist coat and thought- might as well do the whole thing. Then I got the oh s*** moment soon after!

    Jimoz- good idea about roughing it up. Maybe that's a good compromise.
     
  12. Aura noire

    Aura noire New Member

    Ah no worries.

    Trouble is there is not one adhesive manufacturer that would ever recommend tiling over paint of any kind.
     
  13. LJdiy

    LJdiy New Member

    Thank you for flagging this. Im only using very basic 150mm ceramic tiles of 6mm thickness. I've no idea what the calculation would be but I'd assume they wouldn't be too heavy.
     
  14. DIY womble

    DIY womble Active Member

    No need to talk about kiab like that
     
  15. Aura noire

    Aura noire New Member


    What are the tiles made of, and what’s the weight sqm, should say on the box.
     
  16. longboat

    longboat Well-Known Member

    I'd love to know where these 'authorities' on maximum loads/sqm get their data from, and how things are tested.
    I reckon I could use 50 mm thick concrete paving slabs to tile a wall floor to ceiling, if i wanted to, and they wouldn't fall off, or bring the wall down with them.
    Hanging a slab solo in the middle of the wall might be asking for trouble though.
     
    chippie244 likes this.
  17. LJdiy

    LJdiy New Member

    Just looked. 9kg. Phew.
     
  18. chippie244

    chippie244 Well-Known Member

    Crack on :):)
     
    LJdiy likes this.
  19. Aura noire

    Aura noire New Member


    They will be around 9kg sqm add on your adhesive and grout your looking at 13kg sqm.
    If your mist coat is really thin/watery then wire brush over the area to be tiled and prime with a sbr primer you should be ok.
    Remember to tank around the shower area if you have one.
     
    LJdiy likes this.
  20. Aura noire

    Aura noire New Member


    British Standards in conjunction with adhesive manufacturers who spend millions a year on research and development, but hey you know best!!!!

    When it falls down and seriously hurts someone or worse, at least I won’t be someone’s ***** in prison.
     
    LJdiy likes this.

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