More and more frequently pitched green roofs are being seen as providing an important visual design element for modern buildings. There are widespread advantages in specifying green roofs, such as water retention, protection of waterproofing membrane and protection from heat and cold. However sometimes the appearance of attractive vegetation on a pitched roof is seen in itself as being the sole reason to specify a green roof when planning modern and sustainable projects.
BFI Master Film Store
The 45° pitched roof on the new Master Film Store for the British Film Institute is an excellent example of a green roof that adds not only functionality but also an outstanding design feature to the building.
Carol Costello of Edward Cullinan Architects, who were the designers of the award-winning BFI Master Film Store, said: “When it came to the design of the 45° roof at the BFI Master Film Store we chose the Optigreen T-System solution. With not many proven products for pitched green roofs available in the marketplace, we were able to rely on Optigreen’s experienced technical support for this challenging element. The green roof provided a sustainable solution for the building, enhancing the ecology of this rural site.”
Central Parc Prague, Czech Republic
Stefan Zeller, Managing Director of Optigreen explains: “At first glance you don’t even think that it is a roof you are looking at, however an area of 1,000 m² was greened with the Optigreen Pitched Roof solution. The range of possible ways to use a green roof as a design feature for modern buildings is very wide.”
Witchford Recycling Centre
For the waveform roof of the new Witchford Recycling Facility the client selected an Optigreen Pitched Roof Solution. The low maintenance sedum planting will assist with rainwater attenuation and help to blend in the pitched roof with the local rural landscape.
In the UK specifiers and installers still tend to be unsure of the long-term effectiveness of pitched green roofs and fear the risk of a failing design. To ensure even steep pitched green roofs stay looking stunning calls for planning and installation by experienced green roof professionals.
Two factors are particularly important and need to be considered with regard to pitched green roofs: a reliable and permanently functioning anti-slip system and fast-rooting vegetation in the form of pre-cultivated mats to help prevent erosion.
The build-up, in particular the substrate layer, has a propensity to slip necessitating anti-slip measures. Typical tried and tested mechanical solutions involve either the use of a bearer and sill system which transfers the shear force to the roof eaves, or alternatively a netting and sill solution, which instead transfers the shear force across the roof ridge.
The choice of system will very much depend on the shape of the roof and whether it is mono- or duopitch. Under the right conditions permanently functional green roofs on steep roof pitches are entirely possible and have been successfully designed and installed