Washington, DC

Children's National Hospital, Healing Garden


Children’s National wanted to provide patients and their families with a garden where they could enjoy time outdoors. The Bunny Mellon Healing Garden dedicated to the First Ladies of the United States, located on the third level of the original 1970s building, is surrounded on three sides by taller wings of the glass-enclosed hospital and opens toward the city on the fourth side. SGH evaluated the existing roof structure and waterproofing, designed strengthening, consulted on new plaza waterproofing, and designed new structural components for the new rooftop garden.

Replacing even a portion of the roof structure would have been unacceptably disruptive to hospital operations. During our initial study, we determined the existing framing could be strengthened to support the new rooftop garden loads, which exceed 400 psf in some areas, making the project feasible. Highlights of our investigation and design include:

  • Visited the site to assess the existing roof membrane and document the roof structure, primarily consisting of full-story trusses supporting the roof and an interstitial utility level
  • Helped expedite the project schedule by preparing a roof loading plan, which allowed the hospital to secure a permit and begin structural strengthening in advance of receiving a completed landscape design
  • Designed structural strengthening using supplemental framing members that could be transported to the roof on elevators or through small openings in the curtain wall and installed in the crowded interstitial space
  • Developed a staged installation plan to ensure newly reinforced trusses would be loaded as intended in the final condition
  • Designed a new concrete knee wall and roof framing to support a 7ft tall, cantilevered glass wall at the roof edge
  • Collaborated with the project team to address unforeseen conditions during construction

Project Summary



Completion Date


Construction Value


New Construction
Health Care & Life Sciences
Children's National Health System | Perkins+Will
Specialized Capabilities
Building Design

Key team members

Scott Silvester
Scott Silvester
Emily Appelbaum
Emily Appelbaum
Structural Engineering Division Head, Washington, DC