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Closing top of cavity wall

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  • 05-09-2018 9:41pm
    #1
    JJs Left Hand
    Registered Users Posts: 1,219 ✭✭✭


    Acceptable details state that the top of a cavity wall should be closed using a firestopping insulant to allow continuity of roof insulation and cavity wall insulation. I've been specifying Rockwool cavity fire barrier but some contractors not a fan as the bag can't be cut and sometimes has to be bent around a corner making it difficult to close the whole cavity width. Other contractors don't have an issue.

    Anyone know any alternative products suitable for eaves level?


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    #2
    Metric Tensor
    Registered Users Posts: 3,724 ✭✭✭Metric Tensor


    I can't be a whole lot of help other than to add to the complications. The rockwool bags are only available up to 150mm so if the cavity is wider that rules them out too!

    At that width I have been having to specify something like Rockwool SP or Lamatherm but neither of these are ideal and have to be coupled with careful DPC detailing.

    I briefly investigated turning the window/door jamb cavity closers on the flat to close the top of the cavity but after consulting one of the the leading manufacturers it turns out that many of these products have test results specifically for standing upright and no data to prove they can be used on the flat.

    So I would also be interested in other people's experiences.


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