Green roofs are categorized as either extensive or intensive. Extensive green roofs typically only support grasses and small plants, have a shallow growing media depth, and are less expensive to install. Intensive green roofs have a deeper soil base that supports larger plant varieties and can function as gardens, but require stronger structures. Green roofs provide benefits like stormwater retention, increased building insulation, reduced urban heat island effect, and outdoor space for occupants. Proper installation involves layers like insulation, waterproofing, root barriers, drainage, and growing media.