A lack of water is one of the biggest stresses for a green roof of any size, anywhere. However, too much water retained on a roof can cause a number of serious issues that need to be avoided or mitigated:
- Potentially overloading from the increased weight of water,
- Vegetation that does not like anaerobic conditions can be killed off by excess water.
How to best drain a small green roof?
One of the main concerns that small scale builders have outlined to us is how to provide green roof drainage to adequately cope with rainfall of all quantities. In the guide we give rational and simple advice and instructions on the whys and hows of allowing good rainwater drainage.
In the era before commercial drainage layer materials were developed, it was common practice on green roofs to use a thin layer of gravel to act as a drainage layer. The issue with gravel however, is that it is relatively heavy. Thus, in the guide we explore alternative, innovative and creative ways of dealing with drainage for green roofs while also adding to the visual landscape design and increasing the biodiversity potential of the roof.
While you’re on the subject, please also check out our article Vertical Drainage on a Green Roof which looks at some of the novel and interesting ways of dealing with the ‘down’ after the ‘off’.