Greenroof Basics
Extensive, Semi-Intensive, & Intensive
"Extensive" greenroofs are low-cost systems designed to be self-sustaining. They typically contain less then 4 inches of growth medium and can support a variety of plants – especially succulents. This lightweight system requires a structural load capacity of 18 – 30 lbs per sqft, in addition to the local snow load requirements. Extensive greenroofs need little maintenance once established. These systems are aesthetically pleasing substitutes to conventional systems and provide a variety of benefits to the owner and the environment.
"Intensive" greenroofs are intricate systems often referred to as rooftop gardens. Intensive systems are heavy, comprised of more then 4 inches of soil. They incorporate a broader plant range including grasses, trees, and shrubs. Intensive greenroofs, like extensive greenroofs, are dictated by the structural load capacity of the building. An intensive system usually requires regular maintenance and irrigation. This should be viewed as an amenity to a building providing environmental benefits as well as opportunities for recreation.
"Semi-intensive" greenroofs refer to any combination of the aforementioned systems. Semi-intensive greenroofs have some areas with less then 4” of soil, with other areas of deeper soil.