Stormwater Management Roof

Water Retention with a Stormwater Management Roof

Why a Stormwater Management Roof?

Changing weather conditions (e.g. extreme local rain events) can result in an entire public sewerage system being overwhelmed. One of the great benefits of a green roof is that it detains water and allows for the time-delayed run-off of stormwater (water retention).

Water storage in a standard green roof build-up cannot be increased arbitrarily because more water could result in changes to the vegetation used.

However, this is possible with a Stormwater Management Roof which offers this option in addition to all the other features of a green roof build-up.

Features of a Stormwater Management Roof

Up to approx. 80 l/m² of precipitation can be retained with a Stormwater Management Roof and then released into the sewerage system over a pre-defined period (between 24 hours and a few days). The space required for the increased precipitation is created by a grid spacer situated beneath the actual green roof build-up.        

Meanwhile, the elements (water storage for the plants, air-water household in the root area etc.) that are of vital importance for the proper functioning of the green roof are all preserved.

Virtually all types of roof utilisation are possible above the stormwater retention space, once structurally permitted, from an extensive green roof to a roof garden with pathways and driveways.

System build-up

  • 1: Plant Community
    “Sedum Carpet”
  • 2: System Substrate
    “Sedum Carpet”
  • 3: Filter Sheet SF
  • 4: Floradrain® FD 25-E
  • 5: Filter sheet PV
  • 6: Floradrain® FD 60 neo
    as a Spacer
  • 7: Filter sheet PV
  • 8: If waterproofing is not
    root resistant the Root
    Barrier WSB 100-PO
    is required additionally.
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Technical Data

Build-up height:
ca. 160 mm
Weight, saturated:
ca. 170 kg/m2 *
Water retention capacity:
ca. 90 l/m2 *
* Values apply where the full 60 mm are accumulated
The values are typical for Central Europe and vary depending on the actual building and the location. Design rainfall 300 l / (s x ha)