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Void behind drywall open to attic

  • 17-11-2019 12:38pm
    #1
    Bdjsjsjs
    Banned (with Prison Access) Posts: 82 ✭✭


    Hi.
    I am trying to get my head around a feature that I see on some new builds. Basically it seems the void behind the plasterboard on gable ends (or possible all sides open) to the attic. I cannot see the sense in this. As surely, it would create terrible thermal by passes. The pics and diagrams might illustrate better than words can describe.

    I have read online about people who sealed these bypasses with expanding foam (carefully to avoid popping off the drywall) but does that violate fire regulations? Expanding foam isn’t supposed to be very airtight. Would ‘airtight’ brands of expanding foam be enough? Fitting a a/t membrane would be possible in parts but I think very tricky in some parts.


Comments

  • #2
    Bdjsjsjs
    Banned (with Prison Access) Posts: 82 ✭✭Bdjsjsjs


    Also, should the top of the metal tracks be sawn off / covered in foam to prevent them conducting cold down from the attic into the warm side.


  • #3
    Calahonda52
    Registered Users, Registered Users 2 Posts: 12,888 ✭✭✭✭Calahonda52


    Is this detail not one of the fire issues in 100 of apts?
    IIRC the top needs a fire break.. eg when dry lining with timber 2 by 2 say, the first thing fitted is a horizontal piece at top and bottom.
    May be mixing it up..

    “I can’t pay my staff or mortgage with instagram likes”.



  • #4
    Bdjsjsjs
    Banned (with Prison Access) Posts: 82 ✭✭Bdjsjsjs


    Calahonda52 wrote: »
    Is this detail not one of the fire issues in 100 of apts?
    IIRC the top needs a fire break.. eg when dry lining with timber 2 by 2 say, the first thing fitted is a horizontal piece at top and bottom.
    May be mixing it up..


    Could be! This is in end of terrace semi D. It has three floors. I will try to put down a endoscope and see if there is any breaks but if they exist they are rare and not airtight.


  • #5
    Calahonda52
    Registered Users, Registered Users 2 Posts: 12,888 ✭✭✭✭Calahonda52


    Bdjsjsjs wrote: »
    Could be! This is in end of terrace semi D. It has three floors. I will try to put down a endoscope and see if there is any breaks but if they exist they are rare and not airtight.

    Thanks, I may be wrong but 20 years ago when I was doing dry ling I always put in the cross pieces

    “I can’t pay my staff or mortgage with instagram likes”.



  • #6
    Bdjsjsjs
    Banned (with Prison Access) Posts: 82 ✭✭Bdjsjsjs


    By the way the the house in the picture has a airtightness result of 0.236 plugged into its BER xml but that does not mean much to me.


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  • #7
    mike_2009
    Registered Users, Registered Users 2 Posts: 544 ✭✭✭mike_2009


    Thanks for posting this - Got this too in a 22 year old semi-d. Was wondering about insulating it vs sealing it. The plasterboard is dry lined on the back with plastic, not sure if I'll create damp issues if I start sealing it top and bottom (behind skirting). It's definitely open to the attic on the gable end wall, have to check the front and back walls if I can crawl in that far....thermal camera shows problems for sure. The gable end is cavity block, no insulation at all :(


  • #8
    Bdjsjsjs
    Banned (with Prison Access) Posts: 82 ✭✭Bdjsjsjs


    mike_2009 wrote: »
    Thanks for posting this - Got this too in a 22 year old semi-d. Was wondering about insulating it vs sealing it. The plasterboard is dry lined on the back with plastic, not sure if I'll create damp issues if I start sealing it top and bottom (behind skirting). It's definitely open to the attic on the gable end wall, have to check the front and back walls if I can crawl in that far....thermal camera shows problems for sure. The gable end is cavity block, no insulation at all :(


    I think ideally you wouldnt be sealing the plasterboard at all. You would be ceiling your block to your ceiling but how can you ensure that seal is airtight> it is going to be really tricky.Then you have the worry that the block wall is not parged allowing draughts through the blocks. Also they might be full of penetrations that the cowboys knocked out for pipes and wires.


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