To maximise the efficiency of a green roof when it comes to implementing Sustainable Urban Drainage Systems (SUDS), Boningale GreenSky, say that it’s important for designers to have a basic understanding of how plant and substrates work and what the local climate is like.

Maggie Fennell, Technical Green Roof expert at Shropshire-based Boningale GreenSky recommends that green roof designers follow three main guidelines to ensure the best SUDS performance from any green roof; these relate to substrate depth and composition, plus plant combination.

“For substrate depth, 150mm is ideal because it offers the best possible water storage and attenuation, and supports a good, varied range of green roof plants,” explained Maggie. “It’s also important to examine carefully what the local climate is like, because rainfall distribution will majorly impact on the type of substrate you need. For example, we have developed a range of substrates that can store water to cope with drought, or attenuate water to mitigate flooding.”

“Selecting plants that are good for water management on green roofs is essential too, and is often overlooked,” confirmed Maggie.

While water-storing succulents such as sedum, delosperma and sempervivum are particularly good at surviving drought conditions, there are myriad wildflowers and perennials that can live happily alongside them – especially those with leaves that are silvery, hairy or have a small surface area.

“Successful SUDS design is about many different measures working together to control the flow of water around a site. Applying these three rules will mean that a green roof will have the greatest chance of success and efficiency when it comes to water management,” added Maggie.

Boningale GreenSky is the award-winning green roof department of Albrighton-based Boningale Nurseries, who have developed market-leading horticultural products and guidance in partnership with the technology experts at the University of Sheffield’s Green Roof Centre. This research is translated into award-winning design tools that are freely available at www.boningale-greensky.co.uk