An eco-roof, otherwise known as a green roof, is a roof that is covered in vegetation. Whether this is plants, mosses, herbs, grasses, or shrubs, these green and thriving microsystems support the environment by creating a sustainable area on what would otherwise be a barren, unused surface.
Eco-roofs can be categorised into three main sub-categories, extensive, semi-extensive, and intensive. There is no precise, definitive meaning behind each of these categories besides from the growing medium itself; hence the main visible difference between each is the types of vegetation that tends to thrive there.
An extensive eco-roof has a shallow growing medium with a lower roof load, so has a plant diversity limited to species of small mosses, etc. Intensive eco-roofs on the other hand have a deeper growing medium, have more soil, so can support a diverse plant selection sometimes of even small trees or shrubs. Semi-intensive roofs fall between these two.