Roof Gardens in an Urban Hospital
by Lydia Stone Kimball, ASLA

Founded in 1874 by a group of six Catholic Sisters of Mercy in Baltimore, Maryland, Mercy Medical Center is a significant healthcare facility in the city and is a teaching hospital for the University of Maryland. Located in the heart of downtown Baltimore, Mercy is the signature facility in a network of community health centers. The hospital is recognized as one of the nation’s Top 100 Hospitals and has occupied the same site since its initial founding.

The mission of the Sisters of Mercy includes a number of core values: dignity, hospitality, justice, excellence, prayer, and stewardship. These values are especially evident in the nearly completed $400 million expansion of the hospital,  the 18-story Mary Catherine Bunting Center.

Like many urban hospitals, Mercy was faced with the need to improve the care environment of the facility within an aging infrastructure. Now more than ever before, administrators are aware of the benefits to patients, staff, and families of providing an environmentally sustainable healing environment. However, limited expansion space, patient access, funds, and outdoor space, along with a more extensive regulatory process, presented daunting challenges. Ultimately the design team pursued an approach that allowed Mercy to create a sustainable and healing environment as well as a flexible framework for future development. The project features state of the art technologies, energy efficient systems, family-focused care units, an at-grade “‘landmark plaza,” and three rooftop gardens. The decision to remain on the original site created challenges for design and construction, but kept the hospital close to its core location.

The designers embraced principles of both LEED and the Green Guide for Healthcare throughout the design and planning of the facility. These principles are to protect the immediate health of the building occupants, the surrounding and global community, and our natural resources. Specifically, they involve: keeping human health at the core of the design, construction, and operational strategies; incorporating existing infrastructure; enhancing density and connectivity; managing run-off; enhancing or creating habitat for wildlife; and creating outdoor places of respite.

Mahan Rykiel Associates, Landscape Architects (MRA) worked with Ellerbe Becket Architects to develop a master plan for the Mercy campus, including the design of the street level landscape and the three roof gardens.

The new tower addition is immediately adjacent to the existing hospital. It is located on St. Paul Street, a very busy southbound corridor, adjacent to the east-west Route 40 corridor, and two blocks west of the Jones Falls Expressway, an elevated six-lane highway. The building takes advantage of a steeply sloped site to minimize height at the principal façade on St. Paul Street, and the main entrance is actually on the 3rd floor. The deep setback where the gardens are located allows the building to present a relatively modest five-story face at its front and a perceived scale that complements the character of historic Preston Gardens across the street.

MRA’s streetscape master plan addresses the pedestrian and vehicular concerns by narrowing the travel lanes of St. Paul Street by four feet. This accomplishes several goals: it slows traffic at Mercy’s front door, allows the sidewalk to be widened, and creates space for new tree plantings along the edge. The plantings create a more hospitable pedestrian environment, and establish a direct visual link to Preston Gardens. This connection to one of Baltimore’s premier public open spaces affected many of the decisions made by the hospital and the City in developing this master plan.

The design of the building itself and the location of the three roof gardens were intertwined from the beginning. The gardens were by no means leftover space. With a core goal of creating outdoor space and with virtually no site on the ground for that space to occupy, the roofs provided the only opportunity for a meaningful landscape. They were thoughtfully and carefully integrated into the stacking of the building and located adjacent to specific care units.

Kimball - Mercy Roof
Three Mercy hospital rooftop gardens. Image courtesy Patrick Ross. 

The 8th floor maternity and the 9th floor intensive care units have direct access to the gardens. Although it is visible from the adjacent waiting area, the smaller 10th floor garden is not accessible to visitors, only maintenance personnel, but it does provide a valuable stormwater function for the building overall. The gardens are not connected to one another directly, but all are visible from windows in the elevator lobby on every higher floor in the hospital. In this location they serve an important wayfinding and orientation function.

The 8th floor garden offers a bubbling fountain, trellis structure, ample tables and chairs, lush planting with multiple seasons of interest, and a site for a future commissioned sculpture. Paving is dimensional bluestone/flagstone with granite accents and banding. The boardwalk pavers under the trellis articulate the “porch” area and identify it as a seating and gathering zone. Moveable tables and chairs in this area allow very flexible groupings for individuals or families. Seating elsewhere in the garden includes stone benches along the stone dust path and a series of seat walls surrounding the fountain.

The 9th floor garden provides a more intimate space, with more secluded seating areas appropriate for small groups or individual visitors. The focus here is on the green space, with less hardscape overall. Paving consists of boardwalk pavers with granite accent bands. Seating is provided by moveable tables and chairs, a seat wall, and boulders scattered throughout for informal seating and aesthetic interest. The larger lawn area on this floor suggests a calm, less formal garden which is intended to provide respite space for staff and for families.

Both gardens are carefully designed to provide visual interest not only at the ground level, but also from above, as they are visible from every floor of the hospital. Paving patterns create strong and recognizable forms and the granite bands articulate the column grid of the building. These bands also define planting areas and, at 18” wide, can serve as narrow walking paths. The lawn panels on all three levels combine from above to trace a semi-circular form, further defined by bands of plant material. Each garden also provides dramatic views of the Baltimore skyline to the south, east, and north.

The planting design is similar for the 8th and 9th floor gardens. Amelanchiers, Armstrong maples, Clethra, Itea, Fothergilla and Skimmia provide year-round interest, along with a variety of spring flowers, fall color and berries. On the ground plane, Heuchera, Lenten rose, Liriope, Sweet autumn clematis and Sedums provide the same seasonal changes. A Cherry laurel hedge along the back of each space provides privacy for patient rooms, while allowing filtered views into the garden.

While the health-oriented and sustainable elements are clear within the context of the gardens themselves, the larger benefits to the city environment are just as important. The hospital’s commitment to Baltimore City includes jobs and the vibrant community associated with such a large institution. This deep-rooted establishment also contributes to the stable property values in the area. The gardens also contribute to the overall air quality of the city, and by retaining up to 75 percent of a one-year rainfall, they help to improve water quality for the site. The areas also provide habitat for wildlife, which has already begun to inhabit the spaces. Finally, the roof gardens provide a green view to the Baltimore skyline and additional amenity space in the city. Though not technically public spaces, the gardens are available to all hospital users, largely from the Baltimore metropolitan area, and provide places of respite for visitors and staff.

The roof gardens at Mercy’s expansion tower have been installed. The ground level landscape and rest of the hospital are still under construction and are anticipated to be complete and occupied by December 2010.

Lydia Kimball is a Principal with Mahan Rykiel Associates in Baltimore, MD. She can be reached at

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