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Thread: chimney and possible use of fibreglass

  1. #1
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    chimney and possible use of fibreglass

    HI Folks

    We are doing a bit of work in a chimney ( the above roof level part) on a party wall to two houses. The chimney has no dpc or chimney tray in it and it lets water seep down through the chimneys mass in to the building. The site of the house is very exposed ( near sea at elevation here in east coast Ireland). The chimney is a modern concrete block construction , which is rendered in sand and cement. It also has an insitu concrete capping with a 30- 50mm overhang. The chimney is in place about 10 years and its not actually leaking but the whole thing is letting dampness down into the house.

    A suggestion has been made to wrap the whole chimney stack ( above roof level ) in fiber glass ( give is a rain coat). It sounds interesting - but i have a few queries please

    How might the fibreglass be applied to give it really good "fixity" - on to the render - or on osb3 ?
    Will soot or acids from the chimney cause issues for the fibre glass ( or what type should we use)
    I understand fiberglass is uv reactive/susceptible - so its exposure to sun will be total - and we do not want to have to go back up onto the roof for 25 years at least ( if we can help it). Is there a top coat product that can give this sort of protection and is there something else we cna do to assist the fibreglass ( different resin type etc)

    i would very much appreciate your members wisdom - and any technical direction they may point us in.

    many thanks

    JOHN

  2. #2
    Super Moderator Alex's Avatar
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    How might the fibreglass be applied to give it really good "fixity" - on to the render - or on osb3 ?
    Fibreglass can be applied to render with a primer. G4 primer sealer is applied prior to fiberglass, much the same as if you were to line a pond or milking parlour walls, it will bond extremely well.

    Will soot or acids from the chimney cause issues for the fibre glass?
    No.

    I understand fiberglass is uv reactive/susceptible, Is there a top coat product that can give this sort of protection.

    Topcoating is a required part of GRP roofing and pond lining etc. We have roofing resin systems (e.g. metrodeck) that are 20 years guaranteed and there are roofs that are over double that age which are perfectly serviceable. These products are virtually the same ones that are used to build a fibreglass boats and yachts and you really don't want to throw those away within 20 years.

    view the roofing installers guide for more info.

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