Sponge City Roof

  • Green roof in the city

Temporary water retention, maximum water storage and increased evaporation 

This system build-up combines the advantages of an insect-friendly, species-rich extensive green roof with an additional water storage element available to the plants and temporary water retention capacity with run-off limiter. The accumulated water stored in the retention spacer on the waterproof membrane level is available to the plants through the wicking mat. Rainwater is collected above the retention spacer up to a pre-defined level and is discharged at the required flow rate. 

This results in a dynamic development of the vegetation depending on the annual precipitation distribution. We recommend having the final and also the development care and maintenance regime carried out by specialists. Additional irrigation may be necessary during long drought periods during the summer. The accumulated water should be removed during the winter months and, depending on the geographic region, reinstated at the start of the following vegetation period. A roof design with 0° slope is a basic requirement for this build-up.

System build-up


System build-up


* The weight values stated above are considered to be exclusive of vegetation, see Info Sheet "Green Roof Ballast".



Technical Data
Build-up height ca. 16 cm
Weight, saturated ca. 210 kg/m² *
Water retention capacity ca. 107 l/m²

Stormwater Management Roof

This Planning Guide aims to give you a general overview of the technology involved in Stormwater Management Roofs.

Number of pages
16 pages