warm roof construction

Discussion in 'Roofing and Guttering' started by paulandlaura, 13 Oct 2009.

  1. paulandlaura

    paulandlaura

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    Hi
    With warm roof construction, how does the insulation glue/fix to the sub deck and then how does the top deck fix to the insulation prior to either GRP or EPDM.
    Thanks
     
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  3. ^woody^

    ^woody^

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    Fix the first deck of [ply] board, then just lay the insualtion board on top, and then lay the top deck of [ply] board and screw this through to the joists. No glue required

    You can buy insulation with the top layer of ply already glued to it, but IMO you are better off with a separate top deck which you can then cross bond with the insulation to bet a better surface
     
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  4. paulandlaura

    paulandlaura

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    cheers woody. Sorry should have mentioned a vapor control layer over the sub deck.Wouldn't all these screw holes ruin that?
     
  5. ^woody^

    ^woody^

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    No need for a vapour membrane - especially not on top of the sub-deck
     
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  6. noseall

    noseall

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    As Woods has said a 'warm deck' does away with the need for vapour control as the conditions that lead to condensation are no longer present.
     
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  7. PikeyDIY

    PikeyDIY

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    In what way does a warm deck do away with the requirement for a vcl?

    Why would you want to buy two lots of plywood?

    If you have 150mm of insulation, you've got to have some pretty long screws and some pretty accurate drilling to get them into the joists.

    Can't you glue the insulation down to the plywood, and then glue the membrane to the insulation? Celotex 'EL' insulation is specifically designed for this, for example :)
     
  8. noseall

    noseall

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    A 'warm deck' refers to an installation whereby the insulation sits wholly above the rafters or joists. There is NO cold spot hence the words warm roof.

    No cold spot means no condensation.
     
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  10. paulandlaura

    paulandlaura

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    My plans are asking for: Vapour control layer, 12mm marine WPB & 110mm polyfoam roofboard, foil faced and single ply membrane :confused:
    It makes me wonder if my architect understands roof construction because I made it clear to him I wanted a GRP or Rubberbond roof and everyone I've spoken to in them fields recons I also need an 18mm top deck, which isn't on the plans.
    Think it time we had a chat. But your comments would be appretiated.
     
  11. datarebal

    datarebal

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    maybe he does not understand! they dont know everything about everything.. I recently did a job with cement fibre slates.. Archi said he wanted it all stripped off, as he could see the CDRS (rivets) I must have put the slates on upside down!!!!... No sorries after enternit tech support put him right...
     
  12. Roofer

    Roofer

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    A VCL is an essential part of a warm roof construction. It goes above the decking and below the insulation. Single Ply can be mechanically fixed on top of the insulation without the need for another layer of ply.
     
  13. noseall

    noseall

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    Th foil backing to the insulation forms a vcl. My point is there is no need for any additional vcl at, or immediately above ceiling height as the void above is at the same temperature as the room below.
     
  14. slangivar

    slangivar

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    Will putting screws through the insulation not form a cold bridge? This is what my builders did and there are spots on the roof where frost or snow melts first which suggests they are sucking heat out of the house.
     
  15. Xenon

    Xenon

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    Correct, this gives a fair indication to a layman and saves me an hours typing.The vapour barrier should also be carried up the upstand over details to create an airtight connection with the surface membrane of at least 100mm.The insulation is then in its own envolope.

    http://www.greenspec.co.uk/timber-flat-roof-insulation.php
     
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