Insulated plasterboard corners

Discussion in 'Builders' Talk' started by TheHouseThatJackBuilt, Oct 11, 2017.

  1. Hopefully a quick question.... I have a room dry lined with insulated plasterboard, and almost ready for a plaster skim. How do I deal with the outside corners around window reveals? Being the insulated kingspan board, there isn't a batten immediately behind to screw into to hold the beading. The edges of the board butt together 'reasonably' well. Can I use plaster or jointing compound to stick it on? What about the metal reinforced tapes?
  2. BMC2000

    BMC2000 Active Member

    Plaster would be the answer
  3. Devil's Advocate

    Devil's Advocate Well-Known Member

    Hi THTJB.

    Had the same issue when I insul-p'boarded my own room - I hadn't realised what would happen on external corners. I presume you have trimmed away a strip of insulation foam from the edge of one board to the width of the thickness of the whole board? Ie, so that when you overlap them in place, you have continuous p'board on all the outside surfaces?

    It does then make sense to me to bond these overlaps together if there aren't battens nearby (I was ok - there were battens), and I think I'd be tempted to use a very small bead of expanding foam adhesive for this if I had your issue.

    Cut all the panels and test-fit them. Screw one panel in place and then run a small bead of exp foam along the joining surfaces before positioning the other and also screwing that.

    Trim off any excess foam that exudes.

    That way there shouldn't be any cold bridges - which you especially don't want near windows.
  4. Hi, both, thanks for replying so quickly...

    Correct, I cut the insulation away to make a nice joint with continuous insulation on the inside and continuous board on the outside corner.

    So I can 'glue' the edges together effectively with sprayfoam to make a good seal. No need for corner protection at all? Not even tape? - And get the plasterer to skim the lot. correct? I thought corner beads were essential for a good edge. - If required (thanks BMC2000) I can 'glue' the edge bead into place with normal plaster and all will be good. The plasterer can then skim up to this bead for a straight edge if such a thing exists anywhere in this house.

    I've loads of joints between the boards on the flat walls that I was going to tape anyway (believe that's what should be done). I can't plaster to save my life, but if I can save the plasterers time on taping, then I can hopefully save a bit of cash for the next household disaster/upgrade.
  5. CGN

    CGN Well-Known Member

    Best let the plasterer prep it, you won't really save any money and if you get any cracks, they'll blame you :)
  6. Devil's Advocate

    Devil's Advocate Well-Known Member

    Ah, I misunderstood. I didn't realise you were talking about the outer finish.

    You still need external corner beads - make them plastic or stainless steel, not galvanised.

    I agree with CGN - leave it to the plasterer. He will get them set in no time at all, and will do it his way - most likely with some small dabs of plaster.

    If you do them now, by the time he comes the dabs will be dry - and will suck the water out of these spots, so he may have to go round dampening them down or stuff like that.

    Unless you arrange with him beforehand, then don't do it. By all means ask him - he might even say 'Great - that'll be a help'. But don't do it without asking...
    CGN likes this.
  7. awesome. Many thanks. that's one job/ disaster saved.

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