Neighbour building a cavity wall against our new extension wall
Anonymous user 09/03/2024 - 3.15 PM
Hello there - I'll appreciate your views/comments on the below.
We recently got an extension done at our house. Our immediate neighbours, with who we share the party wall are now going ahead with their extension. The neighbour came and asked me he could build his new extension wall as a cavity wall against our extension wall i.e. using our wall as their back wall, adding insulation and the inner wall. As per him it shouldn't be any issue from a structural and build perspective. He also mentioned that he'll join our extension roof with the roof of his new extension via a caping stone to allow for full waterproof and no risk of dampness in the future. He also mentioned that he'll get this written up formally in a party wall agreement to make this official and legal for everyone's peace of mind.
We are in good terms with them and therefore I am not completely against it. However I'll appreciate if anyone can help me understand if there is/are things which I need to be wary of.
Thanks in advance.
Are you a tradesperson and able to answer this question?
I would not let them compromise the integrity of your property and insist it is a separate structure. Under party wall they have to pay the cost of a structural survey to your foundation. You can even insist on who they choose.
Hi,
This is a matter for a Party Wall Surveyor.
I assume that you served a notice letter on your neighbour when you built your own extension. This will have detailed the exact position of the new wall in relation to the common boundary. If your new wall straddled the boundary the neighbour can use the wall you built if he pays half of the construction cost for the wall that you built. However, if you built your wall up to the common boundary but not over it your neighbour must build his own wall on his side. It is more complicated but this is the quick reply.
I strongly recommend that you seek a party wall surveyors advice. Try and find a local company who know the area your area.
Best wishes
Andrew
Hi there , you should of been served with a party wall notice which it sounds like you have . If you have a positive response to this your neighbour then has the right to use the outer leaf of your house ( assuming it forms the boundary) as his outer leaf . He will have to drill wall ties into your wall . This is all pretty standard stuff and nothing to worry about providing he has building control.
Building control will make sure his foundations are correct and won’t affect yours .
If you get along with your neighbour and have any concerns / issues you could discuss with building control .
I’ve just built one exactly like this and had no problems.
Answered20 October 2021
2
Anonymous user
Always a tricky situation as you have to live next to each other. personally I wouldn't want my new roof mucked about with. If your new extension is built right on to the boundry line then they should have the right to do the same. However this is unusual, as to dig foundations to current regulations then there will be concrete extending out from your new building by over 100mm, which would obviously be over the boundry line. So it is usual for an extensions wall to be at least 150mm in from the boundary or more to allow for fascia and guttering etc. To join on to your building they will also need to drill holes in your new wall every 450mm to allow for screw in wall ties. Wouldn't like this myself but i wouldnt want to build right onto a neighbours boundary (other than in exceptional circustances) as it is a minefield of controversy. They will need a party wall agreement in place before they dig foundations within 3m of your property. If your not happy then seek legal advice. Good luck.
