Party wall

A party wall (occasionally parti-wall or parting wall, also known as a shared wall, common wall or 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 also be used to describe a division between separate units within a multi-unit apartment complex. Very often in this case the wall is non-structural but designed to meet established criteria for sound or fire protection, i.e. a firewall.