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Thread: cupping of boards

  1. #1
    Junior Member
    Join Date
    Dec 2015

    cupping of boards

    I have had a fibre glass coating fitted to 22 mm OSB fixed to 50 x25 grounds lathes fixed to a concrete garage roof. there is 25 mm polystyrene in between the ground laths .

    The boards have started to cup upwards causing water ponding . any ideas please.

    The matting runs the same way as the boards do

  2. #2
    Super Moderator Alex's Avatar
    Join Date
    May 2011
    CFS, weekdays, 9-5
    This will happen if the boards are not fixed to the concrete well enough at the edges but also ensure that there are 3-5mm expansion gaps between boards (if they are touching it can push the edges up too).

    So the only option, I suppose, add more fixings at the edges and fibreglass a strip over these new fixings.

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