Hillingdon SuDS Design & Evaluation Guide
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
Detailed <strong>Design</strong><br />
Green & blue roofs<br />
Recent examples in the UK have focused on a<br />
shallow depth of growing medium with a<br />
Sedum (fleshy leaved, drought tolerant plant)<br />
based vegetation. This approach is driven by<br />
cost and the idea of minimum maintenance.<br />
There are now many examples of failure of<br />
planting on this type of green roof due to<br />
lack of drought resillience.<br />
1. A minimum 100mm soil depth is<br />
recommended for drought resilience and<br />
this design is particularly suitable for a<br />
natural dry grassland vegetation.<br />
2. Most green and blue roof substrates have<br />
a water storage capacity of between<br />
30-40% void ratio.<br />
3. A simple orifice control together with<br />
overflow arrangements provides an ideal<br />
opportunity to retain water on the roof<br />
meaning that it does not have to be<br />
stored again at or below ground level.This<br />
arrangement is particularly important for<br />
urban redevelopment where the building<br />
footprint may take up all of the site. This<br />
would be referred to as a blue roof.<br />
125<br />
3<br />
1 2<br />
London Borough of <strong>Hillingdon</strong> <strong>SuDS</strong> D & E <strong>Guide</strong><br />
© 2018 McCloy Consulting & Robert Bray Associates
Change language