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Air Tightness - Attic Space

  • 19-10-2016 11:19pm
    #1
    Wegian
    Registered Users Posts: 220 ✭✭


    All
    In the middle of a self build and now realising the size of the attic means it would be a shame not to include a permanent stairs up and slab out to form 2 additional rooms

    Questions re air tightness detail

    What would the detail at first floor ceiling level / timber to wall intersection?
    I presume I would no longer fit the membrane at this level?

    In the attic - I assume I would fit a membrane to the rafters and slab over them?
    Walls in the attic - Sand/Cement and skim?


Comments

  • #2
    delfagio
    Registered Users, Registered Users 2 Posts: 376 ✭✭delfagio


    This is quite tricky now I would think. If your only deciding now to convert the attic during your build, few main things would be,

    1). Can the joists take the loading of this upstairs attic conversion. Extra support may be required, structurally this would need to be checked
    2). Planning permission may have to be considered
    3). Fire proofing of attic conversion needs to be considered and stair installation to meet fire regs, fire escape from attic etc.
    4). Airtightness membrane needs to be continuous from wall plate up along the rafters back to the other side.
    5). Yes sand and cement plaster required to blockwork but it will very awkward and tricky to ensure that the spaces of blockwork between the joists get properly sealed airtight.
    6). Insulation and ventilated gap and plasterboard required onto Rafters now and service void for cables etc. Hrv ducts, pipes if required for plumbing

    There's quite a lot to think about here to get it all right


  • #3
    rampantbunny
    Registered Users, Registered Users 2 Posts: 907 ✭✭✭rampantbunny


    Wegian wrote: »
    All
    In the middle of a self build and now realising the size of the attic means it would be a shame not to include a permanent stairs up and slab out to form 2 additional rooms

    Questions re air tightness detail

    What would the detail at first floor ceiling level / timber to wall intersection?
    I presume I would no longer fit the membrane at this level?

    In the attic - I assume I would fit a membrane to the rafters and slab over them?
    Walls in the attic - Sand/Cement and skim?

    +1 to delfagios response.

    Regarding the detail itself, you'd need to bring your airtight membrane/tapes from the below the ceiling line, up through your joists and then up along your rafters. You need to seal around every joist as you go. If some joists are doubled up, you need to trace back along the length of the joist and also seal these.
    I've done this on my own build and there's a lot of work and a lot of tape involved.


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