adjacent rear extensions - leave the gap or build a party wall

[Notch7]

Could you get your neighbour to agree to a shared foundation? That way, if the fence is removed and a wider than standard foundation is cast then when you do your build you havent got to dig a trench right next to his foundation. The problem with that is that his foundation, would for a while have an offset load, which the building inspector might not like.

If that is done, there would need to be reinforcing bars cast into the side of the foundation on your side, so when you do yours, the day joint will be locked together (in practice all that happens is that some short length of re bar are hammered into the soil your side.

regarding the specialist foundation you mention -yes you can do that, but eccentrically loaded foundations need structural calculations. In reality there are thousands of such foundations around -where the foundation hasnt been dug very accurately and the cavity wall ends up being close to the edge.

Its a shame your neighbours cant see sense, you are both loosing space and ending up with a more complicated construction for no gain. There are lots of occasions when party wall agreements are best avoided and in those cases building a separate wall makes sense. It sounds like you neighbour is making a decision based on concerns with party walls, but not based on the straighforward circumstances you both have.

In any case if he is going to build very close to the edge of the boundary, he is going to need his builders to work from your side ideally to avoid working overhand and will definitely need to work from your side to get the wall rendered. If he shared a wall it wouldnt need render, so he would save money....

 

[dfk778]

eccentrically loaded foundations

Yes, this is the term I was looking for! Looks like we will need it : (

 

[wessex101]

Yes, indeed. But the problem is now that they build first, so
(1) they can as well to go with their foundations to my side and then what? Can I use their foundations (i.e. extend them further to my side) to build my own and to build a wall on top of these joint foundations
(2) I will need to take care I do not undermine their foundations when I am building mine
(3) they now will be able to build and properly render outside of their wall, and if afterwards I build too close I will not be able to render it, and if the gap is not so small that we can cover it with flashings then elements will be getting in...

nasty..

1. Yes. Don't get bogged down in the details of eccentrically loaded foundations, its a tiny little domestic extension not the Shard. If you really want to get technical just get neighbours builder to incorporate shear keys along the outer face of their foundation so you can butt up to it later.
2. Why the hell would you? (see answer above)
3. Why do you want to render it? Who is going to see it? Just build the outer leaf hidden by extension in dense concrete blocks. The elements "get in" on all external walls and guess what? They're fine.

 

[^woody^]

A gap to the boundary to avoid the PW Act is 1 atom. If you can't measure that, try 1 or 10 mm.

If the neighbour's are building first and want to put a foundation across the boundary, then they will need to serve notice. When that happens you tell them no as you want your own future foundation for your work. They either amend their design and you agree, or you are in despute and surveyors get involved. The resultant award will be the same and they keep their foundation on their side of the boundary and build their wall where they like.

Then when you come to do your wall, the PW Act is not involved, as you won't be doing deeper than their new foundations.

Your strip goes next to theirs but kept separate, and you build right up to the boundary. The PW Act is not involved so there can be no objections. You don't need to render a wall that is not being seen, nor will be exposed.

I've only skimmed through recent posts, but as for foundations, then unless the party wall is shared and the foundations go central, then you don't really want to be sharing one foundation with two walls, and especially when to be built at different times.

 

[Footsoldier888]

Well if they are going 20cm inside the boundary that is not a bad result for you.

There is also any overhang and or guttering to consider when thinking about how near to the boundary to go.

I get the comments about render but if the rest is rendered and is an architecturally designed project it can affect the visual appearance. Just saying!

Sorry I went on about the boundary at such length but the vital thing is you are both in agreement as to where the line is. Disputes can start over these very minor things but once they start they can be very hard to stop. May be worth pegging out.

It seems this one was over a tiny distance for example.

http://www.dailymail.co.uk/news/art...dispute-fence-ends-crippling-legal-bills.html

 

[Nakajo]

'A gap to the boundary to avoid the PW Act is 1 atom. If you can't measure that, try 1 or 10 mm.' Yes, if unsure, don't try to split it.

 

[JP_]

we built a detached living room extension on the back of a semi-detached house. Highly recommended. No noise from neighbours - and you can watch movies with the surround sound pumping (so long as you have good internal doors!) without worrying about neighbours hearing it (or kids sleeping upstairs for that matter).

I'd build the extra wall on my own land, and keep access all around the extension clear for maintenance too.

 

[dfk778]

we built a detached living room extension on the back of a semi-detached house. Highly recommended. No noise from neighbours - and you can watch movies with the surround sound pumping (so long as you have good internal doors!) without worrying about neighbours hearing it (or kids sleeping upstairs for that matter).

I'd build the extra wall on my own land, and keep access all around the extension clear for maintenance too.

Thanks Jonbey, a different angle from most of the posts. At the end it is going to be separate in our case as well, so we will play some music too ))

Many thanks for everyone for such profound discussion and useful comments. I've learnt quite a lot about extensions and party wall matters in the last few days.

 

[RichA]

Thanks Jonbey, a different angle from most of the posts. At the end it is going to be separate in our case as well, so we will play some music too ))

Many thanks for everyone for such profound discussion and useful comments. I've learnt quite a lot about extensions and party wall matters in the last few days.

If you are going to concede some space to allow access, you may want to convince the neighbour to do the same so that you both give up, say, 30cm, to allow 60cm gap for access/maintenance.

 

[^woody^]

You dont need access for maintenance to a sheltered wall up against another sheltered wall, because there will be no maintenance required.

 

[JP_]

I guess you don't need it. I just like it. Makes it easier to clean gutters, put in new tv/sat cables, or just store loads of crap that you don't want to see from the house .... OK, I am most guilty of that!