What do you call a bearing wall that is common to two structures?

A wall that is shared between two adjacent structures is referred to as a party wall. This type of wall serves as a common boundary and is typically a load-bearing element for both buildings. Party walls not only support the weight of each structure but also provide insulation and fire separation between the two buildings, addressing building codes and safety regulations.

In contrast, a retaining wall is specifically designed to hold back soil and is not a common boundary between two separate buildings. A fire wall is an element meant to prevent the spread of fire between two structures and may not necessarily be a shared wall. Finally, a foundation wall is primarily the structural component that supports the building above it, typically below ground level, and does not serve the same function as a party wall. Therefore, identifying a party wall is crucial for understanding shared responsibilities in construction, ownership, and maintenance between adjacent property owners.