Rooftop Gardens

Rooftop Gardens

Rooftop gardens are a potential option for residents of Monwabisi Park. They take up absolutely no ground space because they are on the roofs of the shacks rather than on the ground. Space is already an issue in the park, and creating gardens on the rooftops would positively add to the community’s agricultural proficiency without worsening the park’s spatial conditions. There are, however, concerns with the rooftop gardens, specifically, whether the shacks are sturdy enough to support such systems and whether residents would want and remember to take care of gardens that were out of their sight and reach. An advantage of rooftop gardens is that the layer of soil and plant life on the roof can provide important insulation to the shacks. This fact could prove especially important in the design of the new homes in the redevelopment seed.

Design Aspects

To create a rooftop garden is a bit more complex than creating a container garden, but its benefits in insulation and rainwater filtration could potentially be worth the slightly more difficult installation process. The first layer on the rooftop is a root-resistant layer, which protects the roof from damage by quickly growing roots; it also keeps vegetation to a reasonable size. This Layer should be made out of a thick plastic or sheet metal. Above this layer is a drainage layer, typically made of gravel or foam, dependant on weight requirements. This layer allows for the permeation of water to prevent stagnancy, but prevents precious water from rolling off the roof too quickly. Next is a water permeable cloth layer (similar to a coffee filter) to keep growing medium particles from clogging the drainage layer, followed by a layer of growing medium. Lightweight artificial growing media is an option, other than loam or ground soil, to reduce structural loads. The final step is the planting of vegetation; the climate and amount of light influence this decision (Lui 2005) In Monwabisi Park, the choice of rooftop vegetation would be limited also by the high winds and strong solar conditions in the summer months



As previously stated, rooftop gardens are ideal in urban areas because of their lack of using already restricted ground space. Consequently and advantageously for Monwabisi Park, these gardens also do not use the community soil. Less dense soil must be used to prevent over-weighing on buildings, and in worst-case scenarios, collapse.   In Monwabisi Park, this soil would have to be acquired on a donation-based system, as there is not currently soil existing in the community with the right criteria to support a rooftop garden.

The idea of rooftop gardening is also beneficial from an economically conscious stance. If done correctly, the layers can provide an energy-saving insulation. The thermal advantages of rooftop gardening eliminate the need for insulation in warm, dry climates (Wark, 2003).

Another issue is Monwabisi Park is storm water runoff.  Rooftop gardens can also provide benefits in this area. In addition, drainage and irrigation systems can be designed and put into place for facilitated maintenance of gardens on roofs, dramatically affecting the quantity and quality of the runoff water.  In study conducted in Toronto in 2003, storm water runoff was reduced by 55% per square meter and flow rates by about 85% total. There was also evidence that the garden performance was affected seasonally, in months with more lush vegetation the runoff was reduced by a higher percentage. (MacMillan 2004)

Integrated Redevelopment Efforts

The redevelopment is the best time to attempt an integration of rooftop gardening because structural measures can be accounted for in the design of the new homes. (LINK TO REDEVELOPMENT PAGES WHEN THEY EXIST!)

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