Skimming thermalites

Discussion in 'Plastering and Rendering' started by EdTurtle, 17 Jan 2021.

  1. EdTurtle

    EdTurtle

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    Just after a little advice, I have two questions if thats ok (probably more to follow though). I have removed wall tiles and in places the skim coat has come off, revealing the backing plaster, and in other places removed the skim and backing plaster, and in other places its just removed the adhesive leaving the skim.

    1) Where the the blocks (thermalite/celcon) have been exposed i am going to use bonding to bring it back up the level of the original backing plaster. Should i PVA before bonding, or will wetting be enough? I have had a few cracks where the bonding has dried out quick - despite wetting.

    2) I will be skimming the entire wall eventually, should i skim the bottom half (where the tiles have been removed leaving the backing plaster) to bring it level with the old skim coat, then skim the whole wall in one, or should i just skim the whole wall, so the bottom half would have a bit more skim than the top half - since the top still has some skim left, and the bottom doesn't?
     
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  3. sirocosm

    sirocosm

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    My experience as a DIY.

    1) If you wet with a diluted PVA, say 6:1, it will take longer to dry and then the bonding coat should not dry out too fast and crack. After you apply the diluted PVA, if it dries out right away, apply some more.

    2) I prefer to do the final skim coat in a uniform thickness, as it is easier to trowel that way, so I would do the first option you suggested. Make it all level and reasonably flat first, and then do the skim coat to make it smooth.
     
  4. EdTurtle

    EdTurtle

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    That makes sense, thanks!
     
  5. 23vc

    23vc

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    As above but I’d use hardwall on the high suction blocks after massively soaking them, but either way you can make it work
     
  6. EdTurtle

    EdTurtle

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    Never used hardwall, but i've already got a bag of bonding. Assuming with a bit of pva it'll be ok though? Also, before skimming the old exposed render wall (just the bottom half before a full skim), would i PVA that?
     
  7. Wayners

    Wayners

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    Plastering Pva mix to spec. Let it dry for an hour or so and use bonding.
    Don't worry about it being sticky before you apply and hardwall is good but can't be built out to any great depth.
     
  8. EdTurtle

    EdTurtle

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    Ok, thanks everyone.
     
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