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Single Ply Roof Specification Queries

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  • 27-07-2020 4:41pm
    #1
    prewtna
    Registered Users Posts: 73 ✭✭


    General query on roof specification.

    Have in mind the following (would prefer a metal but money wont allow):

    Single ply membrane with standing seams fully bonded to
    Rigid Insulation (thickness TBC by supplier to comply with u-value requirements and ensure insulation surface is appropriate for accepting fully bonded adhesive etc) also fully bonded (though could be mechanically fixed) through
    VCL to
    plywood deck to
    SW Joists

    Fall of approx 3-7 degrees - roof pitch varies in different locations

    query relates to the single ply membrane - i was speaking with engineer who said the membrane needs to be ventilated underneath - effectively introducing 50mm battens. I understood the above broad-brush-stroke spec would not require any additional ventilation as the attic space is to be kept within the thermal envelope of the building and structural desk is being kept 'warm'.
    Also he raised concerns about the lifespan of the VCL saying some of them (if breathable) can 'block-up' after a period of years.

    thoughts appreciated


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