Low Impact Development Manual for Michigan - OSEH - University ...

Description and Function
Vegetated roofs involve growing plants on rooftops,
thus replacing the vegetated footprint that was removed
when the building was constructed. Vegetated roof
covers are an “at source” measure for reducing the rate
and volume of runoff released during rainfall events.
The water retention and detention properties of vegetated
roof covers can be enhanced through selection of
the engineered media and plants. Depending on the plant
material and planned usage for the roof area, modern
vegetated roofs can be categorized as systems that are
intensive, semi-intensive, or extensive (Table 7.16).
Intensive vegetated roofs utilize a wide variety of
plant species that may include trees and shrubs, require
deeper substrate layers (usually > four inches), are
generally limited to flat roofs, require ‘intense’ maintenance,
and are often park-like areas accessible to the
general public.
Extensive vegetated roofs are limited to herbs, grasses,
mosses, and drought tolerant succulents such as sedum,
can be sustained in a shallow substrate layer (