Each green roof should be tailored to the environment in which it is to be installed in order to achieve the objectives sought from it. The choice of how to achieve the desired finish will be driven by many factors such as cost, desired plant coverage at installation, aesthetics, biodiversity etc.
Whether sedum, wildflower or combined planting, the green roof system chosen will need to be constructed in such a way as to successfully replicate key functions of nature at roof level, these include the storage of suitable volumes of water and nutrients to sustain plant life and drainage or excess volumes of water.
Any green roof system whether extensive, biodiverse or intensive is configured from a number of components that perform vital functions.
Biodiverse roofs, which can also be called brown roofs, use recycled aggregate such as crushed brick and site rubble, and are generally left to colonise naturally or they can be seeded with an annual wildflower mix or local seed source. This creates aesthetic designs as well as aiding biodiversity by creating habitats for local plant and animal species.
The building materials, such as crushed brick and site rubble, used in a brown roof help to extend the life of land refill sites by using recycled building materials on the roof. A brown roof can also contribute to the local, regional and national biodiversity action plans. These systems are generally designed to provide limited access other than general maintenance.
Extensive Green Roof Systems, or 'Sedum Roofs' are an ideal solution for providing an aesthetic, low maintenance ecological feature, which can be admired from surrounding buildings. Due to a relatively shallow growing medium a sedum roof is much lighter in weight, making it ideal for use over most lightweight structures and low sloping roofs. The sedum roof system is designed to provide limited access other than general maintenance.
Intensive Green Roofs, or 'Roof Gardens' are versatile, allowing the roof area to be utilised as a highly aesthetic area for recreation, public access, or simply to be admired from surrounding buildings. Roof Gardens have a deeper growing medium than Extensive Green or Brown Roofs because trees, shrubs, turf, and hard landscaping can be incorporated into the design.
The roof structure will require extra loading capability to withstand the weight of the roof garden and support an irrigation system for maintenance, if required.