Garden roof in Stuttgart, Germany © Optigrün

Extensive green roofs


Extensive green roofs consist of a thin substrate layer and a layer of moss/sedum/herbaceous vegetation, which may be supplemented with grasses. Besides moss/sedum/herbaceous vegetation, special grasses can also be planted; the drawback is that in summertime they often dry out and turn yellow. However, after a rain shower these plants restore. The cooling capacity of dried roofs in summer is less.

Below the substrate layer there is a drainage layer or drainage system, then a root-resistant layer, and below this the roof construction and insulation.

Moss/sedum/herbaceous plants are very suitable, as these plants have the capacity to store large quantities of water and are thus able to survive prolonged dry spells. Moss/sedum/herbal roofs also do not require an irrigation system. Green roofs need to be checked annually for seedlings of larger plants such as trees; these must be removed, as they can damage the waterproof membrane.