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Insulating flat concrete roof externally

  • 25-01-2021 4:59pm
    #1
    Alanstrainor
    Registered Users, Registered Users 2 Posts: 23,157 ✭✭✭✭


    Hey guys, just looking for some info on best practise for insulating a flat roof externally. Essentially we are getting quotes for a complete re-fit of a 1970's house, with insulation and energy efficiency being the main goal. The entire house is going to be re-plastered/drylined internally.

    The house has a converted garage space which is now the kitchen. This space has a flat concrete roof, which currently has a torch felt covering and no insulation. The reason we are seeking to insulate externally is due to space constraints inside. The concrete flat roof is low, and adding 100mm of insulation inside is not ideal in terms of headroom.

    So that brings me to external insulation. Researching online leads me to block insulation with various options for fixing and covering it on top. One of the builders we are talking with mentioned fibreglass and felt, but that sounds like a hack job that would be more at home in the 1980's than now.

    Is there a modern standard practise that I can point to? Or does anyone have any thoughts at all? Any help appreciated!


Comments

  • #2
    Biker1
    Registered Users, Registered Users 2 Posts: 400 ✭✭Biker1


    Alanstrainor wrote: »
    Hey guys, just looking for some info on best practise for insulating a flat roof externally. Essentially we are getting quotes for a complete re-fit of a 1970's house, with insulation and energy efficiency being the main goal. The entire house is going to be re-plastered/drylined internally.

    The house has a converted garage space which is now the kitchen. This space has a flat concrete roof, which currently has a torch felt covering and no insulation. The reason we are seeking to insulate externally is due to space constraints inside. The concrete flat roof is low, and adding 100mm of insulation inside is not ideal in terms of headroom.

    So that brings me to external insulation. Researching online leads me to block insulation with various options for fixing and covering it on top. One of the builders we are talking with mentioned fibreglass and felt, but that sounds like a hack job that would be more at home in the 1980's than now.

    Is there a modern standard practise that I can point to? Or does anyone have any thoughts at all? Any help appreciated!

    You can use a PIR insulation on top with finishes above however you will still be left with thermal bridging around the perimeter. If you could externally insulate the walls as well that would make a big difference.


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