A party wall is a wall that stands on the land of two owners and separates their buildings, or a wall on one owner's land that is used by both to separate buildings. Ownership is usually shared along the line of the boundary, but the useful question is rarely who owns it. It is what each owner may do to it, and that is what the Act answers.
Party wall, party structure and party fence wall
A party wall separates buildings. A party structure is wider and includes floors and partitions between separately occupied parts of one building, which is why flats are caught. A party fence wall is a garden wall standing astride the boundary and not part of a building, and it is covered by the Act while a fence is not.
Who owns a party wall
Where the wall stands astride the boundary, each owner generally owns the half on their land, subject to the other's rights over the whole. Where it stands wholly on one owner's land but separates the buildings, the owner of the land owns it and the neighbour has rights of support. Neither position lets one owner do as they like.
Repair responsibility
There is no automatic obligation on either owner to repair a party wall, which surprises people. What the Act provides is a right to carry out repair work, on notice, and a mechanism for apportioning cost where both owners benefit. A wall that is failing is usually dealt with by one owner serving a notice and the surveyors apportioning.
The semi detached case
In a pair of semi detached houses the dividing wall is the classic party wall, and almost anything structural done to it is notifiable: steels for a loft conversion, a chimney breast removal, underpinning, or a new opening. Terraces are the same with two walls instead of one.
Questions people ask about what is party wall
Who owns a party wall between two houses?
Ownership usually follows the boundary, with each owner owning their side subject to the other's rights. The title plan and deeds are where to check, though for practical purposes the Act's rights matter more than ownership.
Can I attach things to a party wall?
Fixing a shelf on your own side is not notifiable. Cutting into the wall, bearing a beam on it, raising it or removing part of it is, and the difference is structural rather than a matter of degree.
Is a garden wall a party wall?
A wall standing astride the boundary and not forming part of a building is a party fence wall and is covered by the Act. A timber fence is not a wall and is not covered.