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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.

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    • CommentAuthorCharli
    • CommentTimeOct 16th 2020
    1900 house with a tiny 1950s extension. There's damp in the extension, making an internal wall very damp (there's even mould growing on it).
    - original house is 9 inch brick walls, external walls internally insulated with PIR
    - extension is breeze block, external walls insulated internally
    - internal walls bridge the insulation at points, there's no turned-back insulation on them
    - floor is concrete, which does have a dpm in
    - walls have both a slate and injected dpm

    The mouldy wall is in the hallway next to the front door, in the extension. It has gypsum restoration plaster on (the kind with perlite in). And the external ground level is higher than the internal ground level (hence the damp)

    However I can't change the outside ground levels (I don't own the land outside- it belongs to the neighbour). It is concrete up to the side of the house over very shallow services (they literally put the service pipes in on top of the ground and poured concrete on top). There's rainwater drains right up to the side of the house, as well as manholes for the neighbours bathroom. The concrete does slope away from the house.

    Said neighbour is resistant to me doing any work on that land (his grandson lives with him, and has a learning disability and hates noise and disruption). He isn't going to let me dig everything out and relocate the services deeper down! He won't mind me doing some work- french drains or something? However the wettest patch it where the rainwater drain is right up to the brick of the house.

    Any ideas of what i can do to mitigate/live with the damp? In a cost effective manner, without having to do loads of work on land/services that I don't own!
    Check the drain is not blocked/full of silt which could be stopping it draining effectively?

    (edit) Check gutters and down pipes as well.
    I have been very impressed with tanking slurry painted on the inside of the walls. You would have to remove the IWI first, paint the walls 2 coats, then reinsulate. Doesn’t cure the problem, only the symptoms. We had 2 previous properties partially underground that we used it on.
    • CommentTimeOct 16th 2020
    Posted By: Dominic CooneyCheck the drain is not blocked/full of silt which could be stopping it draining effectively?

    Sounds like it is the neighbour's drains so might be difficult. A drain could also be broken/leaking.

    It sounds like Charli needs some specialist legal advice first as to what is possible and what is not and how to proceed. I don't have any relevant knowledge, I'm afraid, maybe somebody else does?
    It sounds like the neighbour is reasonable enough to let you go round and investigate - that would cause no noise or disruption.
    When we moved here 6 years ago, almost every drain trap on the place was blocked with silt. Complete lack of basic maintenance.
    No cost option eliminated first before worrying about the more intensive/expensive stuff.
    • CommentAuthorFairynuff
    • CommentTimeNov 5th 2020
    I have a similar problem - my house is built into a hill and the ground floor is subterranean. Its an old cottage in Devon built of local stone and various methods have been tried over the years to keep the damp from penetrating through from the hillside, none of which appear to have been successful.

    My builder who is experienced with local buildings suggests we tank with slurry, then apply a sticky backed bitumen coat running down to a drainage channel exiting externally and then build a narrow block/brick wall which will give a datum point for fixing the staircase etc.

    I'd prefer to use lime but I'm given to understand this would be a bad idea as the external water level will move inwards as the house warms. Can anyone give any input on the suggested solution of bitumen sheet and if they would suggest insulation or not? Essentially, any input would be gratefully received.
    • CommentAuthortony
    • CommentTimeNov 5th 2020
    If you put an impervious layer on the outside then any moisture moving out through the walls in the form of vapour will hit the membrane and build up till condensation takes place making the wall wet!

    Normally vapour moves out through walls.

    If you can expose the wall on the outside lime pointing or limewash will tend to dry out the wall
    • CommentAuthorFairynuff
    • CommentTimeNov 5th 2020
    Thanks Tony

    Sadly I cannot expose the outside wall at groundfloor level without excavating half of Devon. I can however expose the wall at first floor height which will be cleared of cement render and repointed and rendered in lime.

    In view of the plans for 'tanking' which have to satisfy building control, do you think that the slurry, bitumen with drain plan is a good one or would you suggest another course of action
    • CommentAuthortony
    • CommentTimeNov 5th 2020
    Can’t say re regs but it will stop damp coming in through the wall through itself but not passing into floor or adjoining walls
    • CommentAuthorCharli
    • CommentTimeNov 9th 2020
    The drain was rather slow draining, lots of sediment in there. Its now all been cleaned out! I've also put 'gutter brush' in the gutter that leads down to this drain (which was full of leaves, despite the fact it was cleaned 2 months ago).

    Next doors kid went to stay with other family over half term, so I took the opportunity to cut out some of the concrete, dig down (to below the internal ground level) and fill with perforated pipe and gravel. In the hope it wouldn't hold water up against the wall quite so much.

    Will have to see if it all dries out now!
    That sounds like some progress at least.

    I'm sat here looking up at another leak that is developing on the flat roof over our kitchen...
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