Raising the Bar on Green Roof Design
How does ASLA’s unconventional green roof design perform?

By Theodore Eisenman

Sam Brown

In keeping with a rising tide of green roof design and construction across the country, the American Society of Landscape Architects (ASLA) has recently completed an innovative example of vegetated rooftop at its national headquarters in Washington, D.C. Unlike many conventional green roofs that clothe a building’s existing profile with the requisite structure, soil, and plants, Michael Van Valkenburgh Associates took the green roof standard a step farther by redefining the three-dimensional character of the space.

A defining feature of ASLA’s new rooftop is two symmetrical waves that rise from a central walkway. Finished with galvanized steel decking and a palette of grasses, succulents, and perennials, these geometric berms speak to the idiosyncrasy of green roofs: a naturalistic landscape typology re-created several stories in the air. Unlike many green roofs, however, this one does not conceal its architectonic nature.

“Many people might be surprised to know that Le Corbusier was exploring green roofs as early as the 1930s,” says project manager Christopher Counts, ASLA, of the famed modernist architect. “We drew inspiration from his work and philosophy and made a fairly intentional effort to not hide the industrial character of the roof.”

At first glance, plants share equal billing with wood and steel. But in an innovative gesture that sets this project apart from others, the metal grating that dominates the walking surface floats three inches above low-growing plants. As these sedums fill in, they are expected to peek through the grating, creating a novel interplay between contrasting materials. Over time, one can even envision the ground plane reflecting the movement pattern and desire lines of users.

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