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Vapour barrier or not for pub shed?

Discussion in 'Building' started by bobbiecool, 20 Mar 2021.

  1. bobbiecool

    bobbiecool

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    Hi all.
    I'm building a pub shed and currently in the design stage, readying myself to order the materials. The design of the walls from the outside to in is thus - 25mm shiplap, batons, breathable membrane, 18mm osb, insulation, studwork, internal cladding. The size of the shed is 4.5m x 3m, with a 2m x 2.1m sliding patio door.
    The pub shed would not be used every night of the year, it's mainly a weekend thing in the evenings. In the summer it will not be heated, only in the winter, but like I said only at weekends in the evening for 2 or 3 hours. Given the small amount of time it will be heated in the winter would i need to install an internal vapour barrier to go with the external membrane? To me it would seem like overkill, a bit unnecessary, however any professional would be welcome :)
     
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  3. catlad

    catlad

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    I would say not worth bothering with that limited use, just make sure you vent it behind the shiplap.
     
  4. bobbiecool

    bobbiecool

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    Yes, that’s my opinion too. There’ll be a gap behind the shiplap as I’ll nail it on to battens
     
  5. Notch7

    Notch7

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    what insulation and what internal cladding are you using?

    if you are using celetex insulation board its foil backed so using foil tape to connect them all together will act as a vapour barrier.

    the most important thing that will make the structural weathertight is the air cavity behind the shiplap.


    its an interesting point whether a space that is not heated all the time needs a vapour barrier -I personally would be rather unsure of using any form of plastic in case of condensation -as the inside will definitely get cold

    the problem you have is there will be days when the inside is hotter than outside and days when the inside is much colder than the outside.
     
  6. bobbiecool

    bobbiecool

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    "the most important thing that will make the structural weathertight is the air cavity behind the shiplap". Absolute agree

    "the problem you have is there will be days when the inside is hotter than outside and days when the inside is much colder than the outside." Expected that

    In the walls I'm using Dritherm cavity slabs, mainly to keep the cost down.
     
  7. bobbiecool

    bobbiecool

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    Internal cladding is 12/15mm softwood.
     
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