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Extensive greenroofs are lightweight veneer systems of
thin layers of drought tolerant self-seeding vegetated roof covers using
colorful sedums, grasses, mosses and meadow flowers requiring little or no
irrigation, fertilization or maintenance after establishment.
The
types of plants suitable for extensive landscaping are those native mainly from
locations with dry and semi-dry grass conditions or with rocky surfaces, such as
an Alpine environment.
As a method of surviving extreme conditions, they have developed special
mechanisms such as water storage organs, thicker leaf surface, silver surface
hairs, narrow leaves, etc. (ZinCo, 1998). Minimum soil
depths range between 2 and 3 inches, which is sufficient to support the smaller plant
communities.
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Generally, extensive greenroofs can be constructed on roofs with
slopes up to 33%, and can be retrofitted onto existing structures with little,
or most often, no additional structural support.
The average weight of a fully saturated minimum extensive greenroof is 17 pounds
per square foot, which is comparable to the weight of gravel ballast placed on
many conventional roofs. These
roofs are not intended for recreation, or to accommodate the weights of people, larger shrubs nor
trees. Extensive greenroofs are less costly due to single or double layer
construction.
Link here to see section material
examples of Roofscapes, Inc.'s
four generic extensive greenroof profiles, which include overall depth,
excluding foliage; maximum saturated weight, including foliage; and typical dry
weight, including foliage.
Introduction | History | Extensive Greenroofs | Intensive Greenroofs | Underground Parking Garages | Why | Conclusion
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