party wall

a wall used, or usable, as a part of contiguous structures.

Origin of party wall

First recorded in 1660–70

par·ty-walled, adjective

One day he descended into the courtyard and covered the coach-house, stable, and party-wall with his artistic efforts.

Fromentin |Georges Beaume
Stationing the master's mate as a mark, he laid off five paces at right angles with the first line from the party-wall.

Within The Enemy's Lines |Oliver Optic
The stagnation of life on the Garland side of the party-wall began to have a very gloomy effect by the contrast.

The Trumpet-Major |Thomas Hardy
Then, supposing Monsieur Molineux does allow me to cut a door in the wall, is it a party-wall?

Rise and Fall of Cesar Birotteau |Honore de Balzac

Two adjacent houses were chosen and the party-wall pierced that the ladies might confer with absolute secrecy.

Venice and its Story |Thomas Okey

party wall

property law a wall separating two properties or pieces of land and over which each of the adjoining owners has certain rights