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Code flat roof - no space for ventilation?

Discussion in 'Roofing and Guttering' started by rdougan, 20 Jul 2015.

  1. rdougan

    rdougan

    Joined:
    22 Sep 2014
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    Country:
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    Hey guys,

    I'm doing renovations to my old 1905 house in the Netherlands, and I'm running into issues with our flat roof.

    Basically, our roof has a terrace above. The roof already has flat windows installed, so we cannot have a warm roof as the extra height would be too much for the water to properly drain.

    Previously, there was plasterboard inside on the ceiling, but *no* insulation. So I guess condensation was not an issue. Plus it was not a 'livable' room, so it was done on the cheap - I guess.

    So I went with the idea of having a cold roof. My problem is that I simply cannot have ventilation. The joists run adjacent with the house. At the front side, we have the house (multiple stories) - so we can't put a vent. We also can't do a wall vent because there are big double doors going out to the terrace.

    At the other end, at the end of the house, is the neighbours house. This time it is also only 1 story, so we have the option of having some kind of vent on top of the roof - but is that an option? I've only seen vents on the wall, between the joists.

    Is it possible to do this another way? Perhaps having some kind of device that circulates air? Or perhaps vents on the top of the flat roof? And if so, can I somehow have a single vent instead of multiple vents between the joists (that would be a total of 14...

    Or is there something I am missing. Is it possible to do this without ventilation, but not modify the top/outside of the roof?

    Any help would be appreciated. I'm stuck.

    Facing the front of the roof, where the rest of our house is:
    [​IMG]

    The back wall. Neighbours house behind this wall:
    [​IMG]
    [​IMG]

    View of the roof from above, looking towards the neighbours:
    [​IMG]
     
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  3. noseall

    noseall

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    Location:
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    You could try a full fill method, though this is frowned upon in the UK for various reasons.

    The idea is that you completely fill the space with foam board insulation thus removing any space for moist air. It has to be done robustly and with special attention paid to filling all gaps and using foil tape on all joints etc.

    Another layer of insulation may be necessary across the joists, prior to plasterboarding the ceiling.
     
  4. DIYnot Local

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