Right to Make Use of Neighbour’s Wall Built Wholly on His Own Land

by: The Party Wall Surveyor


In 2004 my neighbour constructed an extension to the rear of our properties and at the time I insisted that the cavity wall of his extension be completely within his boundary. We now wish to build a similar extension and build up to his cavity wall by providing a small 35mm cavity and then a 100mm blockwork wall to provide our internal wall, to maximise our internal space.

He is requesting that we do not use his wall as a Party Wall and separate our extensions. Our houses are victorian terraces with shared 9″ brickwork Party Walls. At the time of his construction he installed an airbrick within his wall to vent the cold space above his flat roof insulation and we have compromised our design height to the airbrick. At the time of his extension we requested his foundations were to be wholly on his side of the boundary. After discussing and to avoid costly foundation design we accepted his strip footing on our side of the party boundary.

Do we have to concede to his request and construct another twin block cavity wall?

He has also requested that we do not damage his render finish, which encroaches onto our land by it’s 20mm thickness. We will need to provide adequate weatherproof flashings by chasing into his render finish. Can he insist we do not chase into his render? He did chase into ours where he needed.


I’m afraid you will have to build an independent cavity wall, or at least a wall that will comply with current Building Regulations in its own right. You have no right to make use of your neighbour’s wall if it is built wholly on his own land.

You do have the right to cut a flashing in to his wall to weatherproof the gap but you will first need to serve a Party Structure Notice. The relevant section of the Act is 2(2)(j): to cut into the wall of an adjoining owner’s building in order to insert a flashing or other weather-proofing of a wall erected against that wall;