St. Louis Zoo Green Roof
When Fox Architects was enlisted to design an animal nutrition center for the St. Louis Zoo, it was decided early on that a green roof would be incorporated into the construction of the "green building." Shield Systems, Inc. was quick to sign on to assist in incorporating the necessary design to assure a successful green roof application. The roof deck is unique to conventional construction as it is sloped in such as way to transition from the building in to the finish grade.
To install the green roof assembly the metal decking was first covered with a high density composite board to provide for a smooth surface. Next, a 215 mil hot rubberized asphalt was installed and flashed into the surrounding perimeter walls and parapets. After the installation of the membrane system, the green roof assembly was installed. First, a root barrier was placed over the membrane to protect against root migration and damage to the membrane. Following the root barrier a geo-composite drainage board was installed. The purpose of the drainage medium is to retain rain water, normally up to 60%. A filter fabric is placed over the drainage composite to prevent the soil from filling the pockets designed to hold water. After the filter fabric a moisture mat is put in place with the purpose of retaining and wicking moisture to the roots of the plantings.
Finally, the engineered soil is installed at an average of 4" thickness. Growing media is light weight and loaded with organics to promote plant growth and provide for moisture retention. With as little as 4" of the specialty soil the roof can support hardy growth of sedums and grasses in an extensive roof application.
In the case of the Orthwein Nutrition Center, a grouping of sedums and grasses were specified by SWT Landscape Architects. Photos show the aggressive growth of the plantings after only one year. The flow of the plantings from the roof to the on grade landscaping make for a seamless transition.
