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Neighbour wants to build a common extension wall - any issues?

Discussion in 'Building' started by Tgeorge, 6 Jun 2021.

  1. Tgeorge

    Tgeorge

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    My semi-detached neighbour is planning to add a rear single storey flat roof extension 4m deep. He has asked if I would be fine to share a common extension wall which he will build at his cost astride our common boundary.

    I plan to extend in future so I am thinking that this will be a good thing for me as we both get some extra space and I will have one wall and side foundation for "free" and almost certainly will get planning permission in future.

    Is there anything I need to watch out for? Or is this never a good idea for any reason?

    I had a long list of thoughts below. Would really be grateful for any feedback

    - Is there any "legal" agreement we need to put in place so that I can exercise my right to use that wall for my extension in future and ensure that he cannot stick guttering or flues through it? Also to make good any damage to our current patio.

    - Should the neighbour finish the wall and foundation in a way that I can attach mine to it easily? e.g. Add a small bit of foundation turning into my property with the rebars sticking out and perhaps leave some bricks/sockets at the end of the wall to attach my wall?

    - Is it easy enough to join up flat roofs?

    - If we ever decide to go beyond 4m (very unlikely as that will wipe out the garden), is there anything to be aware of?

    - if we ever decided to build a double floor extension (again very unlikely) should we get the neighbour to put in appropriate foundations now?
     
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  3. Deluks

    Deluks

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    Watching for replies.
    I'm planning on doing the exact same thing, I am in the position of your neighbour.

    It's the roof join thing I'm struggling with.
     
  4. Tgeorge

    Tgeorge

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    Good to hear. Has your neighbour asked some of the questions I have asked above? In general, I am willing to help out but want these points clarified

    I am wondering what the legal position is? My neighbour and I may shake hands and agree but in future if he sells up and the new owner is not happy to cooperate when I want to attach roof, walls etc, will I be a bit stuffed? Should this be some sort of covenant in title deed so that it does not matter who sells up - that way the agreement to share that wall will remain along with the property.

    I am also concerned if I want to sell, will buyers hesitate because of this which may come up in surveys.
     
  5. noseall

    noseall

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    All property dividing walls in semis are commonly owned. However, that does not mean building a new extension makes that a good idea. We'd always opt for a 150mm gap, to save any future hassles.
     
  6. ^woody^

    ^woody^

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    The legal position is that you have a new party wall just like the one you already have, and you get the same rights to do what you already can do to a party wall.
     
  7. ^woody^

    ^woody^

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    What future hassles can there be with a party wall that is in exactly the same situation as the party wall that is already there?
     
  8. ^woody^

    ^woody^

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    What you need to do in the agreement or the Award, is document that you will be attaching to the wall at some future date and joining the roof. And if you can get this pre-arranged and agreed then that will do away with the need for you to serve your own PW Notice in the future and risk the neighbour dissenting and causing you costs
     
  9. wessex101

    wessex101

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    Several points:
    1. get a written agreement.
    2. get it in writing that the neighbour building the wall will defer your 50% contribution to the new party wall permanently.
    3. I would extend the party wall up with a parapet wall so you will not need to disturb the neighbours flat roof when you build your extension.
    4. make sure the new party wall is built as a separating wall with full sound insulation compliance NOT just an external wall. There is a slight difference.
     
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  11. noseall

    noseall

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    Demolitions future builds etc.
     
  12. charliegolf

    charliegolf

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    This bit in bold... Out of interest, would that carry over to new owners if the neighbour moved?
     
  13. johnny2007

    johnny2007

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    This is very good advice.
    Having the parapet will avoid lots of trouble.
     
  14. ^woody^

    ^woody^

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    PW Awards or agreements should be tied to the property not the person.
     
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  15. Deluks

    Deluks

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    As mentioned, you end up with a party wall, so on a standard cavity wall, the boundary runs through the centre of the cavity.

    Re: Parapets question.

    What's the detailing for a 'back to back' parapet. The correct way is to have cav trays and weep holes on the 'exterior'

    But a second structure attached to the outside of the parapet wall at a later date, then makes the exterior someone else's interior. What's standard practice in these situations?
     
  16. Deluks

    Deluks

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    You would say that, as you are a builder.
    You want to get in, get the job done, get out and get paid. (Understandably)

    Any potential issues with party wall surveys/agreements/neighbours falling out/miscommunication etc. directly affect you, your work schedule, profit and could have a knock on effect on other jobs.

    But that's not a convincing argument that they are a bad idea, (from the clients perspective)
     
  17. noseall

    noseall

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    I'm also a home owner. Mine and my neighbours rear extensions are separated by a trespass buffer zone.

    I can see the sense in what the OP's neighbour is saying, but the gains in internal space don't always outweigh issues that could arise, especially concerning below ground and above the ceiling. Neighbours fall out too.

    It's not something I'd agree to without a fair bit of thought.
     
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