The School Deal That Gave 35XV Its Shape

On West 15th Street in Manhattan, a granite school building supports an unexpected skyline: a glass condominium tower that projects outward, then slopes back toward the sky. This is 35XV, where luxury housing and Xavier High School share a building whose shape makes the arrangement unusually visible.

The school beneath the apartments is central to the story. Its expansion helped make the development possible, while its unused development rights gave the project room to grow. What looks like an architectural flourish is also the physical record of a real estate negotiation.

Designed by FXFowle, now FXCollaborative, with associate architect Beyer Blinder Belle, the project contains 55 residences above its educational base. The American Institute of Architects New York identifies it as a 2016 project. Its most revealing feature is the relationship between the two occupants: each supplied something the other needed. AIA New York

Where it is

35 West 15th Street, Manhattan, New York City.

The valuable space above a school

The transaction began with a familiar Manhattan mismatch. Xavier needed better facilities, while a neighboring development site offered an opportunity to build. The school also possessed something less visible than land: unused development rights.

New York’s Department of Buildings defines development rights as the maximum floor area permitted on a zoning lot. When the existing buildings contain less than that allowance, the difference is commonly called air rights. The term sounds like ownership of empty sky, but its essential meaning is an accounting of allowable building space. NYC Department of Buildings

Those rights become useful when someone can incorporate them into a viable project. In this case, the neighboring property had held a union hall. An earlier hotel proposal involving Xavier’s rights failed to proceed, leaving the school to reconsider how the site might serve its own needs.

According to reporting published by The Wall Street Journal in April 2013, Alchemy Properties acquired the union property for $16.6 million and paid $13.77 million for Xavier’s air rights. The latter covered the new school wing and some furnishing costs. Putting school facilities in the base also helped the project qualify for a community-use zoning bonus. The bargain joined institutional expansion to residential development. The Wall Street Journal

A campus expansion inside a condominium

For Xavier, the outcome was Fernandez-Duminuco Hall, a six-story addition that opened in September 2016. The school describes an expansion of more than 33,000 square feet, including 11 classrooms, four music practice rooms, a theater, student lounges, offices, and a STEAM classroom.

The hall’s name honors benefactor Mike Fernandez, a member of the class of 1972, and former headmaster Vincent Duminuco, S.J. These are the lasting consequences of the transaction: teaching and gathering spaces embedded in a building that also serves a very different residential market. Xavier High School

The project's submission to the Mies Crown Hall Americas Prize describes the school accommodation as enabling residential floor area to increase by an additional two-thirds of its original limit. The educational component was therefore part of the development’s underlying economics. It helped establish how much housing could be built, while the housing supported the arrangement that delivered the school’s addition. MCHAP

That exchange explains why the base deserves as much attention as the apartments. The building’s unusual appearance begins with two programs sharing one constrained site.

The steel table between two worlds

The structural challenge was to fit different kinds of rooms together. School facilities needed broad spaces with few interruptions. Above them, the apartments needed floor plates extending beyond the footprint available below.

Structural engineer Severud Associates used steel framing for the school’s long spans. At the seventh and eighth levels, a steel transfer structure, described as a floor-deep table, forms the support for the residential tower. It projects 36 feet over the rear yard and 17 feet over the existing school.

The two projections use different structural solutions. Trusses support the smaller cantilever. An exposed, sloping framework carries the larger offset’s loads down to the foundations. Above this transition, the residential structure uses reinforced concrete floor slabs and columns. Severud Associates

The visual effect is a tower spreading beyond its stem. AIA New York reports that the cantilevered space accounts for about 40 percent of the residential floor area. That figure describes the residential area overall, rather than a uniform condition on every floor. The engineering allows substantial apartment space to occupy air above places where ordinary vertical supports would conflict with the site below. AIA New York

Why the tower leans away

Expanding outward solved only part of the puzzle. The building also had to fit within rules governing its profile toward the street.

A sky exposure plane is an imaginary sloping boundary that starts above the street and rises inward across a zoning lot. New York uses it to help provide light and air at street level. It regulates the building’s permitted envelope, so additional floor area does not simply translate into permission to build any shape. NYC Department of Buildings

At 35XV, that boundary becomes architecture. Beginning at the 12th floor, the street-facing columns slope inward. Severud explains that post-tensioning in the slab at that level resists the horizontal forces generated at their bases. The retreating profile therefore affects the structure as well as the facade. Severud Associates

The finished building makes these pressures legible: a solid educational base, a projecting residential volume, and an upper profile shaped by the zoning envelope. Its drama comes from giving concrete form to an agreement about space. On this small piece of Manhattan, a school’s capacity to expand and a developer’s capacity to build were negotiated together, then translated into steel, concrete, and glass.

Sources

• AIA New York: 35XV project profile
• NYC Department of Buildings: Development rights and sky exposure planes
• The Wall Street Journal: A School Takes Shape With Condos Above, April 16, 2013
• Xavier High School: 16th Street campus history
• Mies Crown Hall Americas Prize: 35XV
• Severud Associates: 35XV structural engineering