Insulating single skin garage walls

Discussion in 'Building' started by johnny2007, 9 Mar 2021.

  1. johnny2007

    johnny2007

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    Hi everyone, just been to my neighbour and his son is insulating the single brick garage walls.
    I have always put a vapour barrier, then batons 2x2, then insulation and plasterboard (or insulated plasterboard all in one).
    He's missed the vapour barrier and said it's not needed because the garage is dry.
    Is the vapour barrier 100% needed to prevent condensation?
    In my opinion yes.
     
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  3. IT Minion

    IT Minion

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    The vapour barrier is to prevent warm moist air sneaking past the insulation and hitting the cold brick walls, leading to condensation and mold.

    So having it behind the insulation wouldn't help anyway. It should be on the warm side of the insulation. If you're using foil faced PIR and taping the seams then you get that almost for free.
     
  4. ^woody^

    ^woody^

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    Any vapour barrier would go after the plasterboard. Are you thinking of the DPM?

    In any case, vapour barriers are intended for timber frames, and there is no need/no detriment in omitting one from a masonry wall.
     
  5. johnny2007

    johnny2007

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    So what he's doing is correct?
    Batons straight on the single skin walls, insulation on the batons (so basically leaving a 2 inch cavity), than plasterboard.
    Frankly I always used a vapour barrier on the wall, then batons, then the rest.
    That's to create a dry cavity.
     
  6. ^woody^

    ^woody^

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    You seem to be confusing a DPM to stop damp coming across a wall with a vapour barrier which stops moisture going in to the wall from the room side of the wall.

    A DPM can be a good idea if the wall is in a location that gets a lot of directed rain, but is not always essential.

    Forming a cavity when insulating a wall internally is bad design.
     
  7. johnny2007

    johnny2007

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    Vapour barrier =I mean dpm, you're right.
    The same stuff they use under roof batons.
    The breathable membrane.
    Sorry, just getting old.
    I told him that insulation goes in between the batons.
    He's now agreed to that, apparently I misunderstood.
    Getting older...
     
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  9. ^woody^

    ^woody^

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    DPM = polyethene, the same stuff they use under floors!
     
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  10. adeyjones

    adeyjones

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    This is similar to what i'll be doing in an out house and have been advised to leave a cavity between the masonry and the stud frame I need to build for my plasterboarding - should I not then?
     
  11. ^woody^

    ^woody^

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    No, a cavity is a waste of time and space. Just do something along the lines of the above but insulation between and across the battens is better.
     
  12. adeyjones

    adeyjones

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    OK well that makes things easier for me, do I still need a breathable membrane between the masonry and the batons I put on, and if so what's the best way to attach? Just cover all 4 walls with it with some adhesive?
     
  13. ^woody^

    ^woody^

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