Page 130 - Bexley SuDS DESIGN & EVALUATION

Detailed Design Green & blue roofs 2. Most green and blue roof substrates have

Recent examples in the UK have focused on a
a water storage capacity of between
shallow depth of growing medium with a
30-40% void ratio.
Sedum (fleshy leaved, drought tolerant plant)
based vegetation. This approach is driven by
3. A simple orifice control together with
overflow arrangements provides an ideal
cost and the idea of minimum maintenance.
opportunity to retain water on the roof
There are now many examples of failure of
meaning that it does not have to be
planting on this type of green roof due to
lack of drought resillience.
arrangement is particularly important for
urban redevelopment where the building
1. A minimum 100mm soil depth is stored again at or below ground level.This
recommended for drought resilience and footprint may take up all of the site. This
this design is particularly suitable for a would be referred to as a blue roof.
natural dry grassland vegetation.

125

3 1 2

London Borough of Bexley SuDS D & E Guide © 2018 McCloy Consulting & Robert Bray Associates