Green Roofs

Extensive green roofs are designed to reap the benefits that green roofs offer but at minimal cost and with very little maintenance. A shallow layer of growing medium is used to support low growing, stress-tolerant plants such as grasses, mosses and sedums - plants that can generally look after themselves. Apart from being low cost and low maintenance, their low weight means the building’s structure may not need strengthening so sometimes they can be added to an existing building.

Green roofs are generally defined as being either ‘extensive’ or ‘intensive’, terms that indicate their cost, their use and the amount of maintenance the plants need. However, their use also affects the components used in the construction of both the roof itself and the structure of the building.

Intensive green roofs, or ‘roof gardens’, are at the other end of the scale and are often designed to provide recreational space for the building’s occupants. They may contain a wide variety of plants, including shrubs and trees, and will need as much care and maintenance as any garden. In addition, large plants need more growing medium which means the building’s structure will have to be designed to take the additional weight.

Biodiverse roofs are another form of semi-extensive green roof (i.e. low maintenance) that makes use of recycled materials (e.g. crushed brick, crushed concrete etc.) in the growing medium.
This type of green roof is intended to create a natural wasteland and can be seeded initially with selected species to create some growth. However the basic design is to attract fauna and flora of all kinds. As the growing medium is not of high nutritional value, larger plants are not likely to survive and will die off creating further suitable habitat for invertebrates which in turn will attract other fauna.

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