The property where the Ancaya Green Roof Garden Shed is located is topographically situated in a low area that gathers water during large rain events (4″+). Surrounding impervious rooftops are the major source of water runoff contributing to the small flood events. The property owners were in need of a backyard building to house gardening tools and materials but did not want to add to the impervious surface area. A green roof was a perfect choice for this situation. The green roof not only decreases the quantity of rainwater runoff from the garden shed roof, it also provides habitat for insects, birds, and butterflies, is an aesthetically pleasing addition to the urban backyard, and maintains cool temperatures inside the building creating a retreat from the summer heat. We are absolutely pleased with the green roof.

The green roof was designed prior to building the garden shed. This allowed for the design of a structurally sufficient 7:12 roof system able to hold the weight of a fully saturated extensive green roof. Treated 2×4’s were used for slope stabilization positioned 3/4″ above the roof deck allowing water to drain freely bellow the grid. We are extremely pleased with how well the slope stabilization method has performed. The green roof did not slump or slide after the 7.5″ tropical rain event in June 2006.

Because this was a small project (112 ft2, 10.4 m2), 10 mil polyethylene was used as the waterproofing membrane. The waterproofing was trippled to increase the thickness of the membrane. Root barrier cloth (garden store weed control cloth) was used above the waterproofing membrane. The media is 4 inches (10 cm) thick and comprised of three parts PermaTill Expanded Slate (coarse) and one part compost. The plants growing on the green roof include species of Delosperma, Sedum, Talinum, Euphorbia, and Sempervivum (some of the plants provided by Emory Knoll Farms/Green Roof Plants).