Rear extension - building 'against' existing neighbours' boundary wall?

zoothornrollo_2

We are filling in the side return of our Victorian cottage terrace plus going back a bit into our garden - so an 'L-shaped' extension if you like.
On one side (which already has a very short side return extension) we have agreed with the neighbour to build a party wall - great.
On the other they have already extended so there is about ten feet of wall flanking our back garden, built on their side of the boundary. We will be going back to the same extent.
Two separate builders have advised to see if we can build 'against' that 10ft of flank wall 'to save space' - they say we can 'save 30cm', and as it's a narrow plot that will be a significant win.
The architect says that 'won't change the boundary line, but it will make their wall the party wall'.
Don't really understand this.
Do we just ask our PW surveyor to present drawings to them asking what we want, and see if they agree?
They could then appoint their own surveyor, which we would have to pay for? Would that surveyor then advise them against allowing their wall to be the party wall?
Advice from anyone who has been through a similar process appreciated.

ss2020jd

Hi,

We had to do this in our last house.  Both us and the neighbour were building the same type of infill side return extension on a Victorian terrace at the same time. We still got something called a Party Structure notice as we were building astride the party wall centre line. From memory, the party wall surveyor provided the template form and we all signed it. 

I think depending on the type of build will determine whether you need drawings.
 

The first link below explains the basics quite well and goes through the different options. 

The gov.uk site below it outlines everything in detail and has a link to a party wall explanatory booklet and example letters too. 

https://collier-stevens.co.uk/advice-hub/party-wall/serving-party-wall-notices-correctly/

https://www.gov.uk/party-walls-building-works/when-how-tell-them

edited to add: I checked back on my old emails and details and it wasn’t a surveyor it was the person who did the drawings for us. It’s coming back to me now. We decided we didn’t need a party wall surveyor as we were both in agreement and doing the same thing so we just both signed matching forms. 

It did come up as one of the questions when selling but we had whatever was required. 

zoothornrollo_2

Thanks for that - it is quite a tricky situation as there are actually existing extensions on both sides. There's a very short side return extension on the side who have agreed to a party wall. So the party wall will only begin after the end of that.
So whether we can build against that short flank wall on that side is the same issue as on the other side. 
What I can't quite get my head around is: why if we build on our side of the boundary but flush up against their boundary wall - why does that mean their wall becomes 'the party wall'? Why can't there be no party wall - just two boundary walls flush up against eachother?
Is there a difference between building 'against' a flank wall, and building your own structure alongside it? Does there have to be a gap or something?
   

ss2020jd

That does sound a bit trickier. Whilst I’m no expert on the complexities of it, it seems it doesn’t only relate to the wall itself, but even the fact of excavating near it. 

From https://www.gardeningdata.co.uk/construction/party-wall-act.php:

The Party Wall Act comes into effect if someone is planning to do work on a relevant structure, for the purposes of the Act 'party wall' does not just mean the wall between two semi-detached properties, as far as gardeners are concerned it covers: 

• A garden wall, where the wall is astride the boundary line (or butts up against it) and is used to separate the properties but is not part of any building. 
• Excavation near to a neighbouring property.

The RICS have a helpline that can offer 30mins free advice so they could probably advise relating to your specific situation. 

I have heard/read of some cases where party wall surveyors instructed by neighbours charge quite extortionate sums and that in some senses it can be an industry in itself so something to be aware of. 

If you can take any more reading on the matter, this site has useful drawings that explains what circumstances would deem it a party wall 

http://www.boundary-problems.co.uk/boundary-problems/walls.html

Perhaps others who have had experiences of this can add their opinion and advice. 

zoothornrollo_2

Thank a lot for that. Our PW bloke seems to have it all in hand. Made easier by the fact we have decided not to try and bargain with neighbours to gain the extra width.
We will lose maybe 15cm on one side for about a 10ft stretch and the same on the other side for about six foot, so not really worth the bother.
What I am curious about though is this: when you build a new boundary wall up against an existing adjoining one along the boundary line .... what / where is the party wall? Or is there just not PW at all?  

Phil4432

zoothornrollo_2 said:

Thank a lot for that. Our PW bloke seems to have it all in hand. Made easier by the fact we have decided not to try and bargain with neighbours to gain the extra width.
We will lose maybe 15cm on one side for about a 10ft stretch and the same on the other side for about six foot, so not really worth the bother.
What I am curious about though is this: when you build a new boundary wall up against an existing adjoining one along the boundary line .... what / where is the party wall? Or is there just not PW at all?  

Went through something similar earlier this year.

My understanding is that if its in close proximity to an existing boundary, it may fall under the PW act.  Also consider the foundations of any new building, if they are to be deeper than that of a neighbors building that will also fall under the PW act.

You are doing the right thing by having a PW surveyor, this protects you further down the line and keeps your neighbors happy.  Any builder who suggests that you don't need a PW agreement should not be hired.

zoothornrollo_2

Irritating the neighbours we get on best with have asked for their own surveyor, as they are entitled to of course....