A common situation arises when one neighbour has already extended and the adjoining owner later wants to build a similar extension.
It can appear logical to build directly against the existing wall.
But there are several Party Wall considerations to resolve first.
Who owns the wall?
Before designing around the neighbour’s extension, establish the status of the existing wall.
It could be:
- wholly on the neighbour’s land;
- wholly on your land;
- built astride the boundary; or
- subsequently used as a party wall.
Do not assume that a wall at the edge of a building sits directly on the legal boundary.
Can you use the existing wall?
The Party Wall Act contains provisions concerning the subsequent use of certain walls.
Depending on how the wall was originally constructed and the rights available, contribution towards the cost of the wall may arise.
Simple Survey explains this in our guide to Party Wall enclosure costs and making use.
What if you do not want to use it?
You may instead design an independent wall wholly within your own land.
That can avoid some issues but may introduce practical questions around:
- narrow gaps;
- weatherproofing;
- foundations;
- maintenance; and
- access.
Foundations still matter
Even if you do not physically use the neighbour’s wall, excavation for your new foundations may fall within Section 6.
Roof junctions
Where the two extensions meet at roof level, flashing and waterproofing details should be properly designed.
Our article on Party Wall waterproofing and flashing provides further guidance.
Simple Survey can review the arrangement
If you are extending alongside an existing neighbouring extension, send us the drawings.
Visit our Party Wall service page and we can advise on the most practical Party Wall approach.