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Dormer bungalow: insulation and boarding out roof spaces

Discussion in 'Floors, Stairs and Lofts' started by BTC, 30 Oct 2011.

  1. BTC


    19 May 2007
    Thanks Received:
    United Kingdom
    Having read various posts about this problem, I wanted to see what the DIYnot collective knowledge thinks about my situation.

    I live in a dormer bungalow that has an early 1970s loft conversion.

    The ground floor ceiling is topped with about 3cm of fibreglass: I'm guessing this was added at the time of the conversion as it seems to pass under upper floor.

    The electrics are added on top of this fastened to the joists - since it's a slab foundation all the electrics are in the first floor ceiling (no showers or immersion heaters).

    At some point since then someone has haphazardly topped the insulation up to joist level (4" x 1.5" joists).

    The upstairs stud walls between the living space and the loft have about 3cm of fibreglass in them, original 1970s stuff I reckon. Someone has also tacked about 3cm in the rafters with a polythene vapour barrier that is now falling apart. There's also minimal if any ventilation in the eaves and none in the roof space: it looks like the house was designed that way.

    To me it seems like a right b*ggers muddle of insulation and needs a rethink. I want to upgrade the insulation to modern standards, and board the space for storage but am not sure what to do.

    As far as I can see there are two options:-

    - Remove the ceiling insulation down to a minimum level (if any) and board out with a decent air space under the boards (possibly adding extra depth with cross battens). Cut Kingspan/Celotex to fit in the rafters with a 50mm air gap (problem: no tile vents)

    - Lift all cables, reinsulate everywhere up to original joist height, then add cross battens to a decent depth, tack cables to new battens in clear air, then board. Remove rafters insulation and do not replace. Increase stud wall insulation by fixing celotex/kingspan to the loft side (problem: no/little ventilation)

    What does the board reckon I should do? I'm not on a bargain basement budget, but I don't want to spend a fortune and would like to DIY!

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