Groen dak - 004 [atelier GB, Madeleine d' Ersu] © atelier GROENBLAUW

Nature roof


  • Weight: 100-300 kg/m²
  • Depth: 10-25 cm
  • Roof pitch: 0-5° (0-9%)
  • Advantage: Herbs / grasses / sedum, possibly woody plants
  • Water retention: 60-90%
  • Discharge coefficient: 0.4-0.1
  • Water storage: approx. 30-80 l/m²


Garden roof in Stuttgart, Germany

Garden roof in Stuttgart, Germany © Optigrün

Extensive green roofs consist of a thin substrate layer and a layer of moss/sedum vegetation, which may be supplemented with herbs and grasses. Besides moss/sedum vegetation, special grasses and herbs 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 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 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.


© Optigroen

1 vegetation
2 substrate
3 filter mat
4-5 drainage layer
6 protection and storage mat