There’s more to a green roof than meets the eye. Under the surface of a modern green roof lies a hidden build up that not only waterproofs the roof, but protects it from root damage, provides adequate drainage as well as the necessary growing medium to maintain whatever vegetation the roof is intended to support. Going hand in hand with the multitude of technical challenges of designing a green roof there lies the equally bewildering array of choices when it comes to selecting the type of fauna to grace your roof in the first place.
The choice of vegetation on any green roof directly dictates the roof build up, type and depth of growing medium, structural requirements of the roof as well as the ongoing maintenance regime – all of which need to be considered and understood from the outset, making the selection of an experienced green roof architect vital. Grainge Architects have successfully helped many clients through this potential minefield, to guide them to the most appropriate solution for their needs.
Many books have been written on the subject of green roofs, and the subject is far too vast to cover adequately in a short blog, so below we highlight just a selection of particularly interesting and varied schemes that we have completed in the last few years to give a flavour of the opportunities available.
Peter Lanyon Building, Combined Universities of Cornwall, Tremough Campus. – A large, relatively lush extensive green roof, seeded with native wildflowers, this is a roof that seems to change not only with the seasons but year on year. The biodiversity provided by the green roof was instrumental in helping the scheme achieve its environmental BREEAM rating.
Pinhoe & St Nicholas Primary Schools, Exeter – Two large low-fertility Bio-diverse nature roofs. The roofs were left to be steadily colonised by native self-seeded fauna to provide habitat to a wide selection of bird and insect life. The only maintenance required being a yearly check over for invasive tree species and the recovery of lost footballs. The roof provides an oasis for wildlife as well as helping to eliminate the noise of rain drumming on the roof and ensures longevity of the roof at the same time.
RSPB Birdhide, Darts Farm, Exeter – A small scale, low maintenance extensive sedum roof intended to blend into the landscape, and provide a valuable wildlife habitat. The timber-clad building has fixed wires on the facade to aid and encourage climbing plants to further settle the hides into their surroundings by forming green living walls – but this in itself is another topic entirely!
Porthcressa, Isles of Scilly – Several small scale beach-side green roofs situated in a challenging location. Roofs designed and vegetation specified to be native species capable of withstanding the sand and salt of this maritime location.
This small selection of roof types illustrate some of the alternatives to the more commonly recognized sedum or Intensive “Garden Like” roofs much of the public perceive as “green roofs”. Increasingly with green roofs being selected with biodiversity in mind as well as their other benefits such as reduction of rainwater run-off rates and planning aesthetic value, expect to see ever more examples springing up on a roof near you.