Warm GRP flat roof to Cold pitched tiled roof detailing

Discussion in 'Carpenters' Talk' started by Phi99, Apr 23, 2021.

  1. Phi99

    Phi99 New Member

    Hi all,

    Hoping someone could help me detail this roof so that it passes building regs, works (without leaks) and looks good!

    I will have a large GRP flat roof with the rainfall running directly onto a tiled roof.
    I have a design (see attached below); Giving the flat roof a 100mm overhang using some sort of GRP drip trim.

    however theres a few things I'm concerned about:
    A: How do I secure the GRP drip trim as there's only 18mm profile to fix to
    B: Will water get through the 2 trims and cause the pitched roof to get wet?
    C: The 100mm ply overhang should be supported but I can't figure out how to do it other than making a batton on the rafter which means I have to reduce the flashing upstand on the top roof tile.
    D: I also have to be wary that I still need the pitched roof to be ventilated.

    Hoping someone could point me to what sort of trims I could use to make this work, or alternatively tell me an alternative way of doing the entire thing.

    Obvious easy way to do it is the have lead flashing instead of the GRP drip trim but then I would need vents on pitched roof and lead flashing is ugly! Trying to avoid if possible

    Flat roof v8.jpg edit 2 - hosni final drawing incl roof tiles 08-04-21.jpg
     

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