We own a Semi-Detached House and have Planning Permission to erect a Single Storey Extension built on our own Land. Do we need to Serve Notice?

by: The Party Wall Surveyor


We own a semi-detached house and have planning permission to erect a single storey extension to our narrow kitchen.    We originally applied to build the extension to the boundary but the adjoining neighbours objected as it was close to the boundary.    The neighbours had previously built a single story extension 900mm from the boundary and our extension is the same length and roughly the same height as our planned extension.  The neighbours commented at the time that it would look “symmetrical” if we both where 900mm from the boundary, but we explained the size of the extension would be too small for us.  

After we discussed it with the neighbours and considering possible future maintenance access to our property we decided to move the extension 500mm from the boundary.  The architect at the time said this was unnecessary to move the extension, but understood our decision.  He explained there was no structural reason to move the extension as the neighbours’ extension had only been constructed a few years before and would have had to comply with building standards at the time.  The height and length of the wall on their extension would be the same as ours so the foundation depths would be the same.

A few weeks after the permission was granted the neighbours have now stated that they are still unhappy with the proposed extension as it is still too close to the boundary and will most like cause their extension to fall down.  At this point no surveyor has been involved on either side.    They are happy for us to go ahead with the extension if we move the extension 750mm from the boundary giving a total gap of 1650mm.  The additional 250mm difference will somehow stop the extension from falling down, which our architect and builder say is rubbish.  In the construction details of the plans we have also stated that we are building the foundations in one metre lengths to prevent any potential issues, but they says this will still cause the extension to fall down.

I’ve read various resources and the actual Act and I’m not sure if we need to invoke the Act or not. 


You say that your proposals will not require you to excavate deeper than the base of the foundation to your neighbours’ extension but what about the foundations to the original part of their property? Section 6 of the Party Wall Act covers excavation within 3 metres of an adjoining structure (or 6 meters but that wouldn’t apply here) and if the properties are pre-war your new foundations are likely to be deeper than the original foundations.

You neighbours cannot dictate where your new wall goes so long as it is wholly on your own land.

If you do need to serve notice your neighbours have a right to appoint a surveyor and can insist that you appoint a separate surveyor. The Third surveyor is selected by the two appointed surveyors but will only act is asked to do so by one of the parties – normally only if there is a matter upon which the surveyors cannot agree and that is quite rare. The Third Surveyor will decide who pays his fee.


The houses are pre war, but have both been underpinned some years later as there are built on pit land from the early 1900’s.  I would expect the main house founds to be deeper but I guess there is no guarantee.   I’ve only owned the house under a year and the neighbours aren’t reasonable people through my experience and other people in the street.   They have stated there won’t give us permission unless we move the wall, but we will stick to our guns.
Reading the act some of it is open to interpretation, but I’m no expert.  If the foundations on the main house where deeper and I could prove it via building regulations would permission be required?  Also if I believed I didn’t need permission and they said I do how do I stand?


If the 2 houses were underpinned at the same time then you could dig a trial pit on your own land to find out the foundation depth. So long as you are not going deeper there is no requirement to serve notice.

The only option open to your neighbour in that scenario we be to apply for an interim injunction to stop your work although they would have give a cross undertaking in costs should the injunction prove not to have been justified.


I’ve spoken to local building control office and the foundations on the house have both been dug to 1800mm (via records), but they did say the building regulations don’t cover conservatories so there is no guarantee on the foundation depth.  Does the regulation only cover the digging of the foundations?  I’ve also read the regulation don’t apply retrospectively if I could dig the foundations without them knowing.

If the neighbours won’t allow a surveyor access for example and refuse to give their permission as they have said to me what can I do?  Can the party wall surveyor make a decision without them?


All excavation work is covered by the Act; whether it be for foundations or some other purpose. The Act can be invoked retrospectively in certain situations but the more likely scenario is that your neighbours will seek an injunction if they believe the works to come within the scope of the Act.

If the neighbours dissent (by their silence or otherwise) surveyors will have to be appointed and an award agreed. If your neighbour doesn’t appoint a surveyor following a reminder letter from you then you can do that on their behalf. Although it would be desirable for the surveyor(s) to gain access to your neighbor’s property to prepare a schedule of condition it is not essential and will not prevent an award from being agreed.