Green roofs or living roofs consist of a waterproofing membrane, root barrier, drainage layer, growing medium, and vegetation. This system provides multiple benefits including insulation, stormwater management, extended membrane life, and aesthetic appeal. The waterproofing membrane must be specifically rated for green roof applications; standard roofing membranes may be damaged by roots. The root barrier prevents roots from penetrating the membrane. Drainage layers allow excess water to drain while retaining some moisture for plant growth. Common drainage materials include recycled plastic or foam products specifically designed for green roofs. The growing medium (engineered soil) must be lightweight to minimize structural load while providing adequate nutrients and water retention. Typical growing medium weighs 15 to 25 pounds per square foot, adding 300 to 500 pounds per hundred square feet of roof area. Structural analysis must verify the roof can support the combined weight of all layers plus live loads. Vegetation selection depends on climate and desired appearance. Extensive green roofs use sedum and other drought-tolerant plants requiring minimal maintenance. Intensive green roofs can support deeper soil, larger plants, and even small trees, but require more maintenance and structural capacity. Installation begins with the waterproofing and protective layer. Drainage and filter layers are installed. Growing medium is spread evenly. Vegetation is installed either as pre-grown modules or individually placed plants. Irrigation systems may be required in dry climates. Maintenance includes regular weeding, monitoring moisture, and occasionally replacing dead plants. Green roofs last 40 to 60 years with proper maintenance.