Sedum roof © De Dakdokters

Basic green roof


  • Weight: 80-130 kg/m²
  • Depth: 7 cm
  • Roof pitch: 0-5° (0-9%)
  • Vegetation form: Sedum/herbs/grasses
  • Water retention: 50-60%
  • Discharge coefficient: 0.5-0.4
  • Water storage: approx. 25 l/m²


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 light substrate
3 drainage layer
4 protection and storage mat