February 02, 2015
Purchasing a Building with a Party Wall
When considering a purchase of a building that abuts another building, it is critical to understand whether the supporting walls are independent or “party” walls. Many adjoining buildings built in New York before 1930 employed party walls. An owner of a building with party walls often finds that expanding or altering his or her property can be difficult.
Party walls are common walls that support two adjacent structures. The walls often (but not always) straddle the property line, such that a portion of the party wall sits on each piece of property. Each owner, however, cannot modify the party wall without the approval of the other owner. Each property owner holds an easement on the entire wall, and neither can build on it or under it without the approval of the other. The presence of party walls can be determined by examining surveys and reviewing the property records for the property.
This means that if you buy a house with a party wall, and plan to dig out your basement (often requiring underpinning) or add another story, you can’t do so without the permission of your neighbor. If permission cannot be obtained, the only possibility would be employing an expensive workaround, such as building an independent new wall next to the party wall.