Whats the difference between an extensive and intensive vegetated roof?
Commonly, the roof function or objective of the roof space determines the design – is it just an ecological cover or is it intended for human recreation, vegetable gardening, etc.? The limiting factors for vegetated roofs include: the roof loading capacity or maximum dead and live weight loads, determined by a structural engineer; the slope of the roof and perhaps the client’s budget. Extensive – Also referred to as eco-roofs, and low-profile – They have thinner and less numbers of layers, so therefore they are lighter, less expensive and very low maintenance. Extensive vegetated roofs are built when the primary desire is for an ecological roof cover with limited human access. The minimum growing media or soil substrate starts at about 2 1/2″ to 6″ at most (although vegetative mats can actually have even less than 1″ of growth media); the engineered soil media contains 70 – 80% inorganic or mineral material (or higher) to 20 – 30% organic (or less). Low growing, horizontally spreading
