Jun
These are not nearly so labor-intensive as intensive green roofs. They do still need occasional maintenance, such as: irrigation during extreme drought, weeding until the plants become well established, and occasional application of fertilizers. Extensive green roofs are usually installed more for environmental benefits rather than for the enjoyment of the general public.
The soil depth for extensive green roofs is much shallower than most intensive green roof: 3″ to 7″ as opposed to 8″ to 4′. Because of the extreme conditions of many roofs the plants for extensive roofs are typically low growing and very drought and sun tolerant. The plant foliage is usually 2″ to 6″ long and designed to provide maximum ground cover, water retention, erosion resistance, and respirative transpiration of moisture.
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These roofs can be installed over various roofs, but it must first be inspected to ensure that it can bear the load of a green roof. If it is installed on a flat roof another layer must be added to drain the excess water away from the root zone. The best roof slope for extensive green roofs is between 5 degrees and 20 degrees, but, if a grid system is used, they can also be installed on slopes up to 45 degrees.
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