Party wall

A party wall (occasionally parti-wall or parting wall, shared wall, also known as common wall or as a demising wall) is a wall shared by two adjoining properties. Typically, the builder lays the wall along a property line dividing two terraced houses, so that one half of the wall's thickness lies on each side. This type of wall is usually structural. Party walls can also be formed by two abutting walls built at different times. The term can be also used to describe a division between separate units within a multi-unit apartment complex. Very often the wall in this case is non-structural but designed to meet established criteria for sound and/or fire protection, i.e. a firewall.