Tiling and PVA

Discussion in 'Tilers' Talk' started by Mivona, Nov 18, 2017.

  1. Mivona

    Mivona New Member

    Having been told by the builder to prime with PVA, we have subsequently learned that this is not ok.

    The plastered plasterboard and HardIbacker have both been primed with diluted PVA.

    Do we have to sand it all off, or is there anything we can use to go over it before tiling?

  2. fillyboy

    fillyboy Screwfix Select

    If it's a shower or wet area you need to use acrylic primer, this is because pva will revert to liquid form if moisture gets to it. You should be able to get
    most of it off with a wet cloth, damp it gradually to soften the pva or spray with water then wipe off carefully. The hardibacker will be easy enough, the plasterboard will be very easily damaged though so be careful. If the plasterboard is not in the immediate shower area, I'd leave it and just do the hardibacker.
    KIAB likes this.
  3. Mivona

    Mivona New Member

    It is in a shower room, with the shower space entirely lined with Hardibacker. The rest is plasterboard that has been plastered and then primed.

    So, just dampen and wipe off the Hardibacker? Then carefully do the same with the plaster?
  4. fillyboy

    fillyboy Screwfix Select

    Yes, try a test area, spray with water, leave for 5 or 10 minutes to see how it softens up then wipe off with a wet cloth.
    Again, I'm not sure I would be too worried about the areas outside of the shower space, be interested to hear other opinions on this, KIAB, where are ya?
  5. CGN

    CGN Screwfix Select

    What size and type of tiles are being fitted?
  6. Mivona

    Mivona New Member

  7. Wayners

    Wayners Screwfix Select

    Just use a 10mm drill and just break surface every 60mm ish. Keep it neat with a vertical pencil line. I would hold vac to suck dust as you go. Won't take long to do. Spot prime board in drill spots and tile.
  8. Mivona

    Mivona New Member

    What are we supposed to prime with then? If the walls are not dusty, why do they need primed anyway?
  9. KIAB

    KIAB Super Member

    Use a acrylic primer like Weber PR360, BAL Primer,I use SBR diluted 50/50 with water.

    PVA should be BANNED from tiling,for the grief it causes.
  10. yorkshireboy

    yorkshireboy Member

    I know it's not recommended but there,s countless tiles stuck on pva everywhere,can't you go over the pva in the shower area with Sbr.The flaw in the mantra that pva reverts to liquid if it gets wet is that this is also true of the ready mixed tile adhesive,it turns back to mush if it gets really wet.Also unless it's a wet room situation if the surface behind your tiles is wet you will have a problem anyway.
  11. Isitreally

    Isitreally Super Member

    I'm not sure its that the pva will come back to life if it gets damp is the reason not to use it.

    Isn't it that the tiles adhesive will be stuck to the pva and not the actual wall, in the case of large tiles this could cause them to just peel off the wall due to their weight.

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