The Party Wall etc. Act 1996 defines a party wall in Section 20. There are two main types of party walls, described in subsections (a) and (b).
Type A Party Wall — Walls Straddling the Boundary
Section 20(a) defines a party wall as:
“a wall which forms part of a building and stands on the lands of different owners to a greater extent than the projection of any artificially formed support on which the wall rests.”
In simpler terms:
- You look only at the position of the wall itself, not the foundations or any artificial supports beneath it.
- If the wall straddles the boundary line between two properties (even if not equally balanced on each side), it is a party wall.
- The wall must be part of a building — that is, at least one side of the wall encloses some part of a property, such as an external wall of a kitchen or living room.
Type B Party Wall — Walls Built Up to the Boundary on One Owner’s Land
Section 20(b) covers a different situation:
- This type of wall is built entirely on one owner’s land, right up to the boundary line.
- If the neighbour then builds an extension that attaches to and uses that wall as a dividing wall between their building and yours, the part of the wall they use becomes a type B party wall.
- The neighbour must have your permission to do this; otherwise, it is considered trespass. Many property owners are unaware that attaching a building to a boundary wall without permission is unlawful.
- Whether the wall is built right on the boundary line or set back from it, if the neighbour attaches to your wall, it is trespass.
Practical Example
Imagine you have a 4-metre-long, 3-metre-high wall built on your land against the boundary. Your neighbour builds a 3-metre-long, 3-metre-high extension against your wall, with or without permission. Only the portion of the wall that the neighbour has enclosed becomes a type B party wall. The remaining 1 metre that the neighbour did not use remains solely your wall.
Long-Term Use and Easements
- Over time, if the neighbour uses your wall as a party wall continuously for 20 years, they may acquire a legal easement allowing them to continue this use.
- Additionally, you lose the right to sue for removal of the trespassing structure after 12 years due to the statute of limitations.
- This is how many type B party walls come into existence — often without the original owner realising.
If you are unsure whether your wall is a party wall or whether your neighbour has rights over it, consulting a qualified party wall surveyor is strongly advised. Understanding the exact status of your walls helps avoid disputes and ensures compliance with the Party Wall etc. Act 1996.