There are three main types of green roof systems, extensive, semi-intensive and intensive.
Extensive green roofs are usually not accessible and are characterized by lower weight, lower installation cost, lower plant diversity, and minimal maintenance requirements. Modular systems that consist of a flat of sedum rooted in growing media can be installed.
Semi- Intensive / Intensive green roofs are often accessible and are characterized by deeper soil and greater weight, higher installation costs, increased plant diversity, and have more maintenance requirements. Intensive roof systems often provide green space for leisure activities in an ultra urban setting.