Green roofs, aka vegetated roofs, eco roofs and living roofs, are systems for putting living plants on a roof. The goals are to make a beautiful green space, slow and reduce water runoff, cool and clean the air and provide habitat, among others . A green roof system must have a durable waterproof membrane at the base, a layer to provide proper drainage, an appropriate growing medium and plants that are suited for the conditions on a given roof in a given climate. Generally, green roofs fall into two categories, extensive and intensive, with a wide range between the two.
Extensive green roofs have a soil depth of 1 to 6 inches, with the soil depth being dictated by existing conditions and desired outcome. Intensive green roofs are the type where you would see trees and large shrubs planted and can have soil depths of several feet.