What is a greenroof?

Basically, greenroofs are vegetated roof covers, with growing media and plants taking the place of traditional coverings such as bare membrane, gravel ballast, shingles or tiles. The number of layers and the layer placement varies for each system and greenroof type - but at the very least - all greenroofs include a single to multi-ply waterproofing layer, drainage, growing media and the plants, which covers the entire roof deck surface.