New York firm RKTB Architects has completed One Sullivan Place, a mixed-income apartment building that rises 12 storeys and cantilevers in two directions over the rooftop of an adjacent structure.

The building is located in the Crown Heights neighbourhood, near Prospect Park and the Brooklyn Botanic Garden.

Totalling 60,000 square feet (5,574 square metres), One Sullivan Place contains 52 rental apartments, 16 of which are classified as affordable housing.

Of those 16 units, 14 are designated for senior residents. The remaining units are market-rate.

With a ground level that is roughly rectangular in plan, the 12-storey building rises from a corner parcel that was vacant. The parcel faces Sullivan Place and Washington Avenue.

The developer of One Sullivan Place owns that corner parcel, along with an adjacent building that wraps around it.

The neighbouring building has six levels and holds apartments. Appearing as two distinct buildings, the structure has a front facade along Sullivan Place and a front facade along Washington Avenue.

For the empty parcel, the team sought to "maximise the buildable floor area for the small corner site by capitalizing on the air rights of the neighbouring building".

This meant designing a building that extended into the empty spaces above the adjacent building.

"Our team aimed to reconcile the small site size with the considerable amount of developable floor area available to capitalize on," said RKTB Architects managing principal Peter Bafitis.

"The team ultimately arrived at the cantilever strategy that would theoretically allow them to build literally over and above the neighbouring building, but the narrow building frontage posed a significant challenge."

The architects worked closely with engineers to devise a building with "dramatically cantilevered upper stories that spread out beyond the narrow site and over the rooftops of the neighbouring building".

Found on both the north and east sides of One Sullivan Place, the cantilevering volumes are supported by two-storey steel trusses that are 30 feet (nine metre) in length.

"Occupying the ninth and tenth floors, the truss functions as a tabletop to support the eleventh and twelfth floors above," said Nelson Vega, an associate principal with RKTB.

The building's facades are clad in red brick and metal panels. The upper four levels are wrapped in exterior insulation finishing systems (EIFS), often referred to as synthetic stucco.

Large stretches of glass animate the facade and provide occupants with extensive city views.

The views were important to "help fetch competitive market rental rates – an essential component for making it possible to include affordable and senior rental units", the team said.

The team added that One Sullivan Place was one of only a handful projects that were developed under a now-defunct city programme called Privately Financed Affordable Senior Housing (PFASH).

The programme – discontinued in 2021 – facilitated the inclusion of affordable residences for seniors in housing projects by increasing zoning allowances.

Other new residential buildings in Brooklyn include a sail-shaped tower with a concrete-and-glass exterior by Hill West Architects and an affordable housing development by Gluck+ that features brightly coloured facades.

The photography is by Albert Vecerka of ESTO (exteriors) and United Management (interiors).

Project credits:

Architect: RKTB Architects
Structural engineer: GACE Structural Engineers