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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.

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    • CommentAuthordereke
    • CommentTimeJan 3rd 2020
    A friend is having problems with a damp wall. A builder tried to fix the problem by replacing half the roof but a year and £7k later the wall is still damp.

    I've had a look and the house is on the boundary with the neighbour whose driveway runs alongside it with a small gap between. The ground between the house and the driveway is about 50mm below the driveway. The mortar at the base of the wall is cracked, crumbly and in some places missing. The render generally looks OK.

    My theory is that when it rains heavily they are getting a lot of water sitting around the base of that wall and it is soaking in and causing the wall to be damp.

    Is this a crazy theory? Any other ideas for what could be going on?

    I'm trying to attach some pictures..
    • CommentAuthordereke
    • CommentTimeJan 3rd 2020
    pic 1
    • CommentAuthordereke
    • CommentTimeJan 3rd 2020 edited
    pic 2
    • CommentAuthortony
    • CommentTimeJan 3rd 2020
    Unlikely. I would strongly recommend repointing with lime mortar

    Can you post pic from inside

    I also suspect condensation rather than penetrating damp
    • CommentAuthorrevor
    • CommentTimeJan 3rd 2020
    Where is the DPC? .It needs to be 150 mm min above the drive surface. I am suspicious that the brick paving may have been added on top of existing level by not excavating enough for the drive base. It looks like a cavity wall so if it is penetrating from the outside the cavity must be bridged
    • CommentAuthortony
    • CommentTimeJan 3rd 2020
    DPC looks to be one and a half courses up to me and it looks like a cavity wall too so should be OK with wet outside skin
    • CommentAuthordereke
    • CommentTimeJan 3rd 2020
    I'll try and get a picture of the inside for you.
    From memory it felt damp and there were instances of paint blistering.

    In regards to it being condensation I guess that would suggest that inner leaf is too cold? I'm pretty sure it has had cavity wall insulation so i would have thought the walls would be too warm for that.

    They did have a lot of condensation on the windows though and did mention that they try and air it out most days which sounds a right pain.

    • CommentAuthorphiledge
    • CommentTimeJan 4th 2020
    In your pictures it looks like theres 2 vented chimneys on the damp wall. If vented, these are unlikely to have insulation in them so the interior of the old fireplaces/chimneys could be near or at outside ambient temperature. As theres likely no insulation between the vented void and the living space, all the chimney/fireplace walls are likely to be cold and aid condensation.

    Assuming the windows are double glazed and suffering with condensation then the humidity levels in the house may be too high for the level of heating. How warm are they keeping the house? Are they creating excess moisture by drying clothes, cooking alot without extraction, showering alot without extraction etc etc
    • CommentAuthordereke
    • CommentTimeJan 6th 2020
    That is a good point. I will check if the chimneys have been insulated.
    If not how do you insulate a chimney?

    If the chimney has been insulated then what is the solution here? Better extraction/ventilation?
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