How to attach plasterboard to Insulation (PIR) boards?

Discussion in 'Builders' Talk' started by novice_builder123, May 17, 2022.

  1. novice_builder123

    novice_builder123 New Member

    I have cavity walls with concrete breeze blocks externally and Thermalite Aircrete bricks internally.

    We have attached 75mm Recticel PIR insulation boards to the walls using mechanical fixings, to make it strong and robust. Here is a pic of the insulation not attached.

    [​IMG]

    Next stage will be to put a vapor barrier on the insulation boards which is foiled.

    However I have not thought about the next step, which is how to fix the plasterboard to insulation boards.

    I've seen video on Youtube with someone using Pinkgrip Dry Fix foam? However I am skeptical foam will hold.

    Is there a special dot and dab mix you can get that will stick to foil?

    Or should I put a small frame with 25x50mm batten between the insulation boards and then fix the plasterboard to that?

    Any advice or suggestions welcomed.
     
  2. Busterhymen

    Busterhymen Active Member

  3. CGN

    CGN Screwfix Select

    Why would you need a vapour barrier, as the insulation has a foil layer and you have a cavity wall?
     
  4. Busterhymen

    Busterhymen Active Member

    It only has the barrier on both sides!
    I agree with you but the OP could be talking about bridging shielding the open/cut end of the PIR to the window frame in the picture, before affixing the plasterboard. There is little room for vapour barrier PIR to fit across the gap. The OP would have needed to have considered this before ordering windows plus frame spacers if PIR was to be used for the recess return, so may now have uninsulated window aperture.
     
    Last edited: May 17, 2022
  5. novice_builder123

    novice_builder123 New Member

    This is a renovation of an extension built in the 70s. Its coastal and some of the cavities are, well, not great, built by locals

    Rooms are massive so I am trying to shrink as much space to heat as possible. I think I will do batten frame between the PIR and PB.

    All walls will not be load bearing, just sockets.
     
  6. CGN

    CGN Screwfix Select

    You would have been better battening the walls first, then fit the insulation and Pb.
     
  7. Busterhymen

    Busterhymen Active Member

    Presumably there is an unmentioned 'something' to space the PIR from the wall (there's a gap in the pic).

    OP - did you cut the PIR with a chainsaw?
     
  8. CGN

    CGN Screwfix Select

    Think he mentioned it wasn’t attached in the pic. Regardless, he’s gone about it the wrong way.
     
  9. novice_builder123

    novice_builder123 New Member

    There's some bridges in the cavity, until I get some waterproofing externally there will be damp coming in. You can see in the photo around the window opening

    Im reluctant to put stud partition that would rot in that situation being fixed to the cavity wall, especially putting PIR boards between it and the breached cavity wall.

    I cut the PIR with a Bahco hand saw for fine cut, but will use a stanley blade in future.
     
  10. CGN

    CGN Screwfix Select

    nothing wrong with using a hand saw, I didn’t see any issues with your cutting.

    If you were worried about damp, then you could have put a dpm on the wall before attaching your battens/lath. Doing it this way, you could have straightens and plumbed up any discrepancies with the brick work before fixing the pir and Pb.
     

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