Iowa Stormwater Education Program

Design Details

There are three main types of green roof systems, extensive, semi-intensive and intensive.

Extensive green roofs are usually not accessible and are characterized by lower weight, lower installation cost, lower plant diversity, and minimal maintenance requirements. Modular systems that consist of a flat of sedum rooted in growing media can be installed.

Semi- Intensive / Intensive green roofs are often accessible and are characterized by deeper soil and greater weight, higher installation costs, increased plant diversity, and have more maintenance requirements. Intensive roof systems often provide green space for leisure activities in an ultra urban setting.

  • Green roofs are more conducive to flat or gently sloping roofs.
  • Design consideration must be given for the weight of the green roof.
  • A root resistant waterproof membrane is installed to protect the building.
  • Drainage is needed to handle the excess water flow from the roof. A variety of lightweight aggregates or a synthetic drainage framework is place on the waterproof membrane below the soil media.
  • The types of plant materials used is dependent on climate, irrigation, maintenance, depth of media, and how the green space will be used. Shallow roof media requires more drought resistant plants such as sedums. Deep roof media expands the range of plants that can be used. Shrubs and trees are often include in intensive roof systems.
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