Does my Neighbour Have to Leave a Gap Between His Extension and my Building?

by: The Party Wall Surveyor


We live in a link detached property where our neighbours garage links to the side of our house with a space behind their garage.

They have written to us using the party wall act saying that they would like to utilise this space and build a conservatory behind their garage which would mean that one side of the conservatory was one side of the remaining part of our house and the other being their house.

We have signed to say we are in agreement subject to further information, however now reading further into this, is this really a party wall or does this stop where their garage ends.  My main concern is that we bought the property as a link detached property but would this then be classed as a semi-detached and in effect de-value ours.  Can we stop them doing this?  Or can we insist that a gap is built between the conservatory and our wall and if so how much gap should be provided based on ensuring damp proofing etc.


From your description it would appear that the part of the side wall of your property which your neighbour’s garage encloses is a Type B party wall . The rest of the wall would not be party and as such your neighbours will not have a right to build up against it without your consent.


Thank you for your advice – I have over the weekend received another letter this time from their builder with some new plans for a rear extension (now not a conservatory but a single storey extension) being built behind their garage.  He has stated that they will leave a gap between our wall and their proposed extension so that it is completely independant from our house but to utilise a small lead gutter to prevent roof water falling into the small gap between the walls and causing a damp problem.

I am obviously again concerned with this as there is the danger of birds, animals and general debris getting stuck in the gap plus if there was any danger of our walls needing work carried out in the future this would be impossible. 

Is there a legal gap which has to be left between the two walls and do I have any rights to stop this building work happening?  I really don’t want to appear unreasonable but having only moved into our house at the end of March am feeling quite stressed over all of this.


You neighbour has a right to build right up to the boundary line but not over it – that includes the parts of the new structure higher up such as the guttering or fascia. There is no minimum gap that must be left. In situations such as this it may be beneficial to allow your neighbour to cut a flashing in to your wall to protect the gap from moisture or debris.

As your neighbour will be excavating alongside your building they may be required to serve notice under section 6(1) of the Party Wall Act (if they will be excavating lower than the base of your foundations). You would then have an opportunity to appoint a surveyor at their expense. That surveyor could then check the flashing detail for you.


Does this mean that the boundary line is actually the side of our house i.e. the part which is uncovered but belonging to us?

What would happen if in the future we needed work done on our outside wall which would now have no access – surely there must be something that would cover us for things happening in the future?


I couldn’t say where the boundary is without visiting the site and even then it may not be obvious.  

By the sounds of it you would have required your neighbour’s consent to go on to his land to maintain the side wall of your property. If it is just a wall it is unlikely to require any maintenance and once there is a building up against it it will be protected from the weather. There are no laws to stop an owner from building on their own land provided he has the necessary planning consents. The only exception that I could think off is if there was a window in the wall and you had acquired a right to light.