Bringing Rooftop Gardens To Ground Level

In Columbus, OH, building a green roof into an existing structure provided an innovative solution for parking needs and open space for an urban park.

By Amy Taylor

Cities across the nation are embracing green spaces as a viable development tool due to their many benefits, but as urban areas begin to attract more residents and visitors, they also attract an increased demand for parking space. How can developers satisfy parking needs while also creating open spaces for urban parks? Building a green roof into an existing structure is one innovative and effective option.

The Columbus Commons, a multi-use park in the heart of downtown Columbus, serves as a successful example of how cities can use urban space efficiently to bring life to downtown centers while still offering necessary facilities like parking.

green roof urban parking
(Photo credit: Randall L. Schieber)

Previously the site of a nearly-vacant urban shopping mall, Columbus Commons was designed by the Columbus Downtown Development Corporation (CDDC) to establish a community green space in the city’s downtown. The mall was surgically removed to preserve the garage beneath with a large portion of Columbus Commons built on the roof, creating both a prominent city attraction in one compact area and an unobtrusive parking area for visitors and local businesses to utilize.

The project, completed on-time and on-budget for $25 million, has already generated more than $400 million in private investment around the park. The project’s meticulously planned infrastructure and economic success offers developers a comprehensive solution to deal with conflicting demand for parking and land development, while enjoying six acres of sought-after green space as their backyard. CDDC continues to manage Columbus Commons as a seasonally programmed award-winning event space, offering more than 200 events for the community to enjoy. The challenges of day-to-day operations on a green roof over a parking garage are outweighed by the tangible benefits of having a thriving gathering space that serves as the signature space in downtown Columbus.

Prioritizing Sustainable Development

During an era of heightened awareness of human impact on the planet and increased migration to urban centers, sustainable infrastructure and eco-friendly development is crucial for urban planning. Developers must keep in mind the effect of structures on the vitality of the area as well as the people within it.

In the case of Columbus Commons, the section of the park located above the underground parking garage was developed as a green roof. The garage roof is a post-tension concrete slab, in which the roof was poured so that the cables and posts hold it in place. All the landscaping in the area of the park above the garage was driven by what the concrete slab is capable of holding.

The green roof concept can be replicated on any rooftop, and as demonstrated by Columbus Commons, that rooftop can be at ground level. The primary benefit of green roofs is that they help reduce the occurrence of heat islands, a phenomenon that happens when concrete and urban structures replace vegetation and cause temperatures to rise in the area. Green roofs can reduce city-wide temperatures, cut building energy use and filter the air we breathe.

While the initial destruction and replacement of existing structures can often be extremely wasteful, the demolition project to take down Columbus’ City Center mall recycled an estimated 80% of materials in addition to preserving the underground parking garage – setting a sustainable model for future redevelopment projects.

Staying Accessible And Efficient

Once a facility or area is developed, the battle to attract and keep business begins. While many areas are working to increase multimodal and ridesharing transportation access, dropping car ownership is not yet an option for many Americans due to suburban sprawl. Offering easy downtown parking helps attract visitors from the surrounding areas who are reliant upon cars, but the presence of abundant surface parking lots often makes a destination less desirable, and cuts into walkability.

Currently, more than 30 percent of space in many downtown commercial areas is taken up by parked cars. As development demand increases, the need to use these sprawling spaces more efficiently grows as well. Paid parking options are still essential to many developing areas, as they have been shown to increase revenue and boost sales for local businesses. A viable solution is to offer abundant underground parking, which uses land efficiently while making sure the area is accessible to visitors.

Consideration For Future Projects

The presence of green space in urban centers is a growing trend, cited as having emotional and physical health benefits for residents. Moving parking underground creates room for these centers of urban activity and real estate investment to coexist.

green roof urban parking
(Photo credit: Randall L. Schieber)

The benefits of green space are numerous and varied, ranging from increased quality of life, visitor attraction, workforce retention, storm water management savings, and reduced individual healthcare costs.

For developers looking to use urban space efficiently, promote private investment, build sustainably and ensure the long-term vitality of an area, building green roofs, and bringing them to the ground level is a great way to reach these goals. Columbus Commons is more than just a success story for our downtown; it’s a road map for how to build in the future.

Amy Taylor has more than 20 years of experience in the field of operations, public policy, and communications. Currently, she serves as the Chief Operating Officer for the Columbus Downtown Development, where she has played a lead role in the transformation of Downtown Columbus, such as the Scioto Mile, Columbus Commons, and the Scioto Greenways river revitalization project, and the National Veterans Memorial and Museum.