Plasterboard dot and dab issues

Discussion in 'Builders' Talk' started by Sam9696, Feb 12, 2023.

  1. Sam9696

    Sam9696 Member

    Hi all,

    just had walls dot and dabbed.

    long story short, the walls are brick sand limes that suck the life out of anything.
    The plasterer used a roller and put a one coat of PVA prior to boarding.

    Following day, one board sounded blown, it bassically came off with minimal effort. Rest of boards look ok, however it’s put doubt in my head now. If a dab is on the wall, If “tapped” with a hammer will just come off as one whole dab. Surely this isn’t right as I’ve seen people having to use SDS to get the dab off the wall before due to how solid it is.

    The dots used appear too small and weirdly doesn’t look like it really “grabbed” the back of the boards (see pics)

    Should SBR have been used on these bricks? And not sure why the back of the boards appear to not have bonded properly.

    Would appreciate any advice.


    Attached Files:

  2. arrow

    arrow Screwfix Select

    Get the job rendered and set or hardwall plaster and set. A better job all round rather than lashing some plasterboard to the wall.
  3. Jord86

    Jord86 Screwfix Select

    He should have dilute PVA’d it the day before to seal any dust, then dabbed it the next day or so. Was there a damp issue with the wall? Or he’s used out of date bonding compound, or mixed some of it in a dirty bucket, this will have accelerated it curing so wouldn’t have gripped the board with suction well enough.
  4. Sam9696

    Sam9696 Member

    Bucket was dirty I saw yes, but the point im trying to make is the pic that shows where the plasterboard has stuck to the board the big chunk is where it has properly bonded.

    In the past whenever pulling a wall off, the board would break and the dabs would be stuck to the wall still with the remaining board also.

    But it looks like it’s just “pealled off” in one whole piece if that makes sense, hasn’t taken any board with it on the majority of the dabs Shouldn’t be able to pull it off as a whole piece like that surely
  5. CGN

    CGN Screwfix Select

    it needed to dry longer.
  6. Sam9696

    Sam9696 Member

    So how long till it’s fully set And properly bonded?

    Why would some adhesive dab grab properly and the rest not if applied with the same mix at the same time on the same board?

    i get to fully cure can take time but to form the initial strength and bond should be achieved fairly quickly ie - being able to skim the following day.
  7. CGN

    CGN Screwfix Select

    dabbing technique aside, the dabs in your photos have all pulled the paper off the board.

    You are relying on the paper bonded to the gypsum core to grip the adhesive and hold the board on.

    What happens when paper is kept damp?
  8. Sam9696

    Sam9696 Member

    think you’ve hit the nail on the head there.

    boards were delivered on a dry day and straight into the house. Only thing I can think is they had been stored In a damp condition.

    As you say, this weakened the bond between the paper and core?

    please elaborate on the dabbing technique aside? Sorry for the questions just trying to see on the best way to proceed arguably it’s the boards that are s*** which is very frustrating
  9. CGN

    CGN Screwfix Select

    You’re missing the point.

    You have a blob of wet adhesive against the paper on the board which initially weakens the bond between the paper and the board until it dries out. There is little air flow behind a Pb, so the dab takes a good few days to dry out properly. Until this point it is still ‘green’. You can usually easily remove a tile the next day, even when rapid set has been used because the adhesive is still green. It is the same in this case.

    There is nothing to elaborate on the dabbing technique.
  10. Sam9696

    Sam9696 Member

    yes i get this, however if that were the case, the dabs would set near enough at equal rates, it has been 5 days now since it was done and if pulled slight pressure, the board would come off as a whole piece, which if bonded the board would break as opposed to one piece as the adhesive is stronger than the board.

    I do understand what your saying.
    Just not convinced that the adhesive adhered properly To the back of the boards, I could be wrong.
  11. CGN

    CGN Screwfix Select

    dabs are quite thick and also vary in thickness. Roughly a mm per day to dry out given good conditions. I’d be more concerned if they pulled off the wall.

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