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Mercy Hospital


The Extensive Garden Roof® Assembly is ideally suited for locations that will receive little maintenance or where structural capabilities are a concern.

Unlike the Intensive Garden Roof Assembly, the Extensive Garden Roof is not intended for recreational use and is typically chosen for its appearance or to help reduce the "urban heat island" effect and minimize stormwater run-off. Extensive roofs only require a shallow growing media depth, generally as little as 75 mm to 150 (depending on the region), and therefore add little weight to the roof structure below when compared to a standard ballasted PMR roof.

Recommended plant types for extensive roofs need to be drought, wind and frost resistant, such as self-generating sedums, herbs, grasses and other vegetation that can withstand harsh growing conditions.

The water stored in the growing media and drainage/retention layer is sufficient to sustain the drought resistant plants between periods of normal rainfall. Thinner assemblies and very lightweight growing media blends are available for Extensive Garden Roof Assemblies. Contact us for specifics.

Features of the Extensive Garden Roof Assembly:

  • Depth of growing media between 75 mm and 150 mm
  • Reduction and delay of stormwater runoff
  • Attenuation of the urban heat island effect
  • Minimal maintenance required
  • Use on flat or sloping roofs
  • InstaGreen® GT-4 tray available for modular applications
  • Vegetation options - Plugs, Sedum cuttings, InstaGreen® sedum carpet or InstaGreen® sedum tile

Typical Application:

An Extensive Garden Roof Assembly can be applied to flat roofs and sloping roofs with a pitch of up to 12:12 (45°), provided the appropriate measures are taken to cope with the shear forces and soil retention. Extensive roofs are typically lightweight and can be installed over a variety of structures including metal roof decks.


Extensive Garden Roof