Green roofs have been a part of building for over a thousand years. The current green building movement has, however, had the greatest impact on the growth of the green roofing industry.
A green roof is commonly defined as a roof that consists of vegetation and soil, or a growing medium, planted over a waterproofing membrane. There are two basic types of green roofs, an extensive roof, which has a few inches of soil cover and an intensive roof that has two feet or more of soil for a variety of grass, trees, bushes and shrubs.