Overlooking Underpinnings: A Recipe for Disaster

An article in the latest Historic Districts Council newsletter (pdf only) explores what can happen when owners fail to adequately underpin an old building’s foundation—and it ain’t pretty. According to the story, it’s dismayingly common for construction crews to dig around houses or attempt to remove interior structures on party walls without proper shoring, which can lead to building collapses (and sometimes damage neighboring properties). And a lot of landmark Brooklyn homes are particularly at risk. Here’s why:

Pre-Civil War structures have foundations typically made of rubble—roughly mortared fieldstone—rather than the cast reinforced concrete with spread footing common today. The 19th century buildings are especially vulnerable to digging next door. The vibration pulverizes old mortar, leaving loose stones free to shift and fall. SEAoNY counts one or two underpinning failures each month, mostly in Brooklyn on small one- to six-story projects.

The DOB’s oversight of underpinning is considered lax by groups like the Greenwich Village Society for Historic Preservation, which is lobbying the city to step up regulations for structural work on historic properties.
Historic Districts Council