A green roof, living roof, or vegetated roof are all terms used to describe a partially or completely covered roof with vegetation over a waterproof membrane. There are two types of vegetated roofs, intensive or extensive. The difference is simply the depth of the planting medium.
The traditional vegetated roof uses larger plants and a deeper soil to support the root growth. Newer technology has allowed for a lighter planting medium that supports sedum plantings, but would not work for larger plants.
Vegetative roofs are not a new concept, having been developed originally in Germany in the 1960s. They have become more popular with the benefits of added insulation, reduced storm-water runoff, habitat creation, and protection of roof membranes. Vegetative roofs also benefit the reduction of heat island impacts in the urban setting.