An explanatory guide to the Party Wall etc. Act 1996
3. What is a party wall?
The Act recognises two main types of party wall.
Party Wall type (a)
A wall is a "party wall" if it stands astride the boundary of land belonging to two (or more) different owners.
Such a wall:
• is part of one building (see diagram 1), or
• separates two (or more) buildings (see diagram 2), or
• consists of a “party fence wall” (see diagram 3).
A wall is a “party fence wall” if it is not part of a building, and stands astride the boundary line between lands of different owners and is used to separate those lands (for example a garden wall). This does not include such things as wooden fences.
Party Wall type (b)
A wall is also a “party wall” if it stands wholly on one owner’s land, but is used by two (or more) owners to separate their buildings — see diagram 4.
An example would be where one person has built the wall in the first place, and another has butted their building up against it without constructing their own wall.
Only the part of the wall that does the separating is "party" – sections on either side or above are not "party".
The Act also uses the expression "party structure". This is a wider term, which could be a wall or floor partition or other structure separating buildings or parts of buildings approached by separate staircases or entrances (for example, flats) — see diagram 5.