MBB’s Grace Church High School Expansion is featured in Architectural Record‘s “Continuing Education: Vertical School Expansions.

Continuing Education: Vertical School Expansions

By Katherine Logan

Jan. 2, 2019

Building on top of another building is nobody’s first choice. Issues of structural capacity, construction logistics, approvals for extra height, and aesthetic and programmatic relationships make it almost a last resort. Yet, for urban schools that need to grow, raising the roof is often the only option. “Real estate is incredibly challenging for many of these institutions,” says Mary Burnham, a principal at New York–based Murphy Burnham & Buttrick Architects (MBB). “If you can’t expand to the right or left, it’s very logical to look at air rights as potential for development.”

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Vertical School Expansions

In New York City, where real-estate pressures are squeezing buildings ever upward, MBB has also built several rooftop extensions for schools, especially in cases of adaptive reuse. Grace Church School, for example, established the high school component of its program about seven years ago in what was originally a mid-19th-century row of dwellings, planning to add a gymnasium in the future on the roof. Recently completed, the school’s 14,000-square-foot extension provides large multipurpose spaces that can accommodate courts for team sports as well as all-school gatherings and events.

Daylight in the New Gymnasium

An array of long skylights in a new, arched steel roof works with large windows to let daylight into the addition, and a palette that includes exposed steel structural elements, glass, and wood complements the school’s original building. The expansion also adds offices, locker rooms, and storage areas, as well as a new fitness center. Designed for flexibility, the athletic facility doubles as a performance space for theatrical productions; the new space for storage makes for ease of transformation.

Long-span spaces like gymnasiums represent one of the key opportunities of rooftop additions, says Burnham, where a large, open volume can be designed without structural responsibilities for loads above. That doesn’t mean the construction of Grace Church’s athletic center was without structural challenges, though. The historic building that houses the high school program has a single brick facade, but consists structurally of multiple smaller buildings of lightweight construction—wood-frame, with some steel—that were incapable of supporting the load of the new gym. The first phase of construction entailed reinforcing the original structure.

Overcoming Design and Engineering Challenges in School Expansion

New steel members were tied into the existing columns to augment their capacity and carry the new loads to existing foundations. “It was a lot of work,” says Burnham. The addition also presented sound-transmission issues. To separate the noise of basketballs thumping on the gym floor from conversations in the classrooms below, the athletic facility sits on a jack slab lifted on springs above the original roof level, with a 5-inch air space between the two slabs providing an acoustic break. But solving that problem complicated elevator access. An existing elevator, recalibrated to serve the extra story, couldn’t quite account for the jack slab, so subtle ramps make up the difference. More straightforward is the stair access: a wide existing flight was extended to reach the new floor, with overscaled glazing above to bring daylight deep into the floors below.

Respecting the Urban Context

Like Vera Hartmann, Burnham says that working a rooftop extension into the fabric of an existing building poses a major design challenge: “Do you make it look as if it has always been there, or do you make it look like a new thing sitting on top of the building?” she says. Ultimately this may not be up to the architect. To win approval from the city’s Landmarks Preservation Commission, which oversees development applications in Grace Church School’s historic district, the boomerang-shaped roof of the new construction conforms to a sight-line-defined envelope that conceals it from street view. The resulting form, says Burnham, “emerges out of the roof as an object. Even though it’s invisible from
the street, it creates its own identity, and contributes to the school’s. It’s a wonderful thing to be all in one place at once.”

MBB’s design for the Grace Church High School Athletic Center won a 2020 Design Award of Honor from the National Society of American Registered Architects, a 2020 Best of Design Award from the Architect’s Newspaper, and a 2019 Design Award from the American Institute of Architects New York State.