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public roof - retention

Retention public roofs are paths and areas that can be used by people, cars and trucks while also functioning as retention areas. They can be combined with green areas on the roof. Retention traffic roofs can be used on uninsulated roofs as well as on warm and inverted roofs.

This variant of roof greening benefits the principle of the sponge city. The aim behind this is to ensure a better urban and microclimate. This is achieved by retaining rainwater and keeping it where it falls. The green roofs also delay evaporation. The sponge city thus absorbs water and releases it again with a delay. This improves the urban climate. Our green roof traffic roof retention also contributes to this.

System structure public roof - retention

Note: Click on the marked points to get more information!

Top layer

  • Pavement or slab covering, covering height depending on load class

Bedding material

  • E.g. bedding stone chippings 0–5 mm (30–50 mm)
  • Screed layer for surfacing material

Base layer

  • Base layer of gravel 0-32 mm resp. 0-45 (height 150 mm minimum)

Filter fleece FIL 300

  • Prevents fine particles from forming sludge in the drainage layer
  • high water permeability
  • very high robustness class GRC 5
  • learn more: Filter fleece FIL 300

Water retention box WRB 85, WRB 95 or WRB 170*

  • Infiltration trough made of recycled PP intended for surface drainage in combination with a Flow Control System
  • high water retention potential
  • learn more: WRB 85
  • learn more: WRB 95

  • learn more: WRB 170

    * Selection according to load class, roof construction and required accumulation height. Please contact our Technical Department.

Protection, seperation and slip layer SGL 500 and seperation and slip sheet TGF 0.2

Technical specifications

Weightfrom 400 kg/m² or 4.0 kN/m²
Build-up depthfrom 250 mm
Roof pitch*0°
Load class1-3 (max. 20 t vehicle weight)

* Roofs with zero degree falls do not meet FLL Green Roof Guidelines and Optigrün systems should not be used without consultation.