Component: Green roofs

SuDS Green Roof


Green roofs comprise a multi-layered system that covers the roof of a building or podium structure with vegetation cover/landscaping. The roof is likely to consist of an impermeable layer, a susbstrate or growing medium and a drainage layer (although not all green roofs require a drainage layer).


Green roofs are designed to intercept and retain precipitation, reducing the volume of runoff and attenuating peak flows.


Advantages and disadvantages


  • Mimic predevelopment state of hydraulics and hydrology

  • Good removal capability of atmospherically deposited urban pollutants

  • Can be applied in high density developments

  • Can be retrofitted (reliant on site specifics)

  • Ecological, aesthetic and amenity benefits

  • No additional land take

  • Improve air quality

  • Help manage urban heat island impacts

  • Insulates buildings against temperature extremes

  • Reduces the expansion and contraction of roof membranes

  • Sound absorption


  • Cost (compared to conventional roof)

  • Not appropriate for steep roofs

  • Opportunities for retrofitting may be limited by roof structure (strength, pitch etc)

  • Maintenance of roof vegetation

  • Any subsequent damage to waterproof membrane likely to be more critical since water is encouraged to remain on the roof












Where component can be used?

Residential:  Yes
Commercial/industrial:  Yes
High density:  Yes
Retrofit:  Yes
Contaminated sites:  Yes
Sites above vulnerable groundwater: Yes



Peak flow reduction:  Medium
Volume reduction:  Medium
Water quality treatment: Good
Amenity potential:  Good
Ecology potential:  Good



  • Irrigation is needed during establishment of vegetation for some roofs

  • Inspection for bare patches and replacement of plants will be required on a regular basis

  • Litter removal may be required (depending on setting and use)


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