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670 Union Street

Brooklyn, NY
  • Photo credit: Matthew Williams.

Located near the boundary between Park Slope and Gowanus, 670 Union Street is billed as the city’s first modern mass timber condominium. Glulam beams and floors are architecturally exposed in the building’s 14 units. The development is also aiming to meet Passive House energy efficiency standards, incorporating features such as solar panels, EV charging stations, and all-electric heating and cooling.

The six-story structure consists of a one-story steel and concrete-on-metal-deck podium topped by five stories of GLT planks on glulam beams and columns. The floor structure was originally designed as CLT panels, but the project ultimately moved forward with GLT due to the building code in effect at the time of DOB filing.

Silman designed large-section glulam beams for column transfers and used steel straps and plywood splines to connect the GLT planks into a single floor diaphragm. Units on the top three levels have cantilevered balconies supported on perpendicular GLT planks that extend past the facade.

The condo building’s lateral system is CMU shear walls at the core and on two sides. Shallow foundations support a one-story cellar. The main roof contains a recreation space, while a rear extension over the parking area serves as a private roof deck.

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