Advice for new extension adjoining neighbours extension

[Webbers]

Hi,

I am starting to think about adding an extension to the rear of my property. As you can see in the attached photo, my neighbours house already had an extension, which was build about 8 years ago by the previous owners (also before we moved in). I have marked a blue line on the photo where I believe the boundary is. As you can see the external wall of the neighbours extension is about 6 inch within their boundary.

Ideally I would like to build right up to the extension, i.e. use their external wall as my internal wall. Not because it will give us slightly more room but I would be concerned about the future problems of a small gap between the extensions. The footprint and height would be exactly the same as my neighbours extension. I have not yet spoken to my neighbours about my plans but they seem to be reasonable people so I'm not too concerned. However, I would like everything to be done properly to avoid any issues when selling.

I'm basically after some expert opinions on what I'm suggesting and if there is a better way to approach building it. I understand that I would have to serve a party wall agreement but would there be any issues down the line relating to the 6 inches of my property that would actually be on my neighbours land.

Any advice is much appreciated.

 

[charliegolf]

Well it's a boundary. And when they come, boundary disputes are a nightmare, where only lawyers win. As well as needing to sort out the land issue (will you maintain their boundary line after your extension is up; or will you want 6" of their entire garden?) you may create some kind of 'flying freehold' where you own property on their land. Anything can be done, but I would not leave it at, "Oh we came to an agreement...". I think I'd rather have a maintenance gap (18-20") and stay on my own land.

 

[Old Salt]

Surely you would build another block wall that would form the cavity. Talk to the neighbour and see what they think.

 

[Webbers]

Yes I see what you mean. So have a cavity at my neighbours side and a cavity at my side and share the brick wall in the centre as the boundary. Do you think that would get round the fact that the external brick wall in slightly on the neighbours side of the boundary?

 

[JohnD]

you need to pack the cavity with rigid (not nestable) insulation to prevent a cat or rat getting stuck there.

The two roofs need to be bonded in some way so water and rubbish cannot get into the gap .

A dense wall is better at blocking noise than a lightweight wall.

 

[^woody^]

If their wall is 6" in on their land, you can't serve a PW notice and hope to use it.

You could try and serve a notice to build a new shared wall on the boundary, but that will potentially cost you a lot of money for very little gain.

Have someone design a suitable wall on your side of the boundary.

BTW, the common misconception of a gap between two extension walls being a problem in terms of water or rubbish or anything is a nonsense and no issues occur in real life.

 

[Webbers]

Thanks for your reply Woody. I am now thinking that a separate wall is the way to go. I’m thinking I can build a double skin wall with about 300mm gap just at the edge of my patio doors. It’s good to know your views on there been no real issues with a small gap between properties.

I won’t get into the planning side but do you know if building with a small gap between properties (about 6 inch from my boundary) would still come under permitted development. Or does building this close to a boundary require planning permission.

 

[Notch7]

BTW, the common misconception of a gap between two extension walls being a problem in terms of water or rubbish or anything is a nonsense and no issues occur in real life

I've certainly heard that a fair few times from clients.....some sort of urban myth.

There must be thousands of small gaps in England done to avoid a party wall.

 

[mattylad]

I am not a builder however...
If your going to leave a gap between outer walls then I'd make it as small as you can, because unless someone can fit down it to do anything then it's pointless having a bigger gap.
I'd look at something like a 50mm (ish) gap so that while building the wall, after the pointing has been done (overhand) then a sheet of kingspan can be shoved down it.

 

[^woody^]

Thanks for your reply Woody. I am now thinking that a separate wall is the way to go. I’m thinking I can build a double skin wall with about 300mm gap just at the edge of my patio doors. It’s good to know your views on there been no real issues with a small gap between properties.

I won’t get into the planning side but do you know if building with a small gap between properties (about 6 inch from my boundary) would still come under permitted development. Or does building this close to a boundary require planning permission.

You can build up to the boundary under PD. The issue tends to be the roof verge or soffit overhang, so the wall would be set back to allow just for this.