An Extensive green roof has a shallow growing medium containing little nutrients which is suitable for less demanding and low growing plant communities. In Extensive green roofs, landscaping is designed to be more self-sustaining, requiring less maintenance and fewer expenses than other systems. Since they are lighter and require less structural support, they are well suited to roofs with little load bearing capacity. They are often not accessible. Extensive green roofs are often suitable for retro-fit installations on existing buildings, due to their relatively low load implications, although structural engineers must be consulted for any such applications.
Semi-Intensive Green Roofs in terms of requirements fall in between Extensive and Intensive Green Roof. More maintenance, higher costs and more weight are the characteristics for this green roof type compared to that of the Extensive Green Roof. It can be accessible but it is more likely to be only overlooked.
Intensive Green Roofs have a deep growing medium that supports a variety of landscape design and growth. They add considerably more weight to roofs; thus requiring additional structural support and added costs. They are mostly accessible and are used as recreational spaces, therefore safety features should be considered to allow public access. The amount of maintenance for Intensive green roofs is the highest among the three types of greening. There are no limitations in design and individuality.