Green roofs

Green roofs are vegetated layers that sit on top of the conventional waterproofed roof surfaces of a building. Green roofs are designed to be sustainable and have a number of benefits for the environment. Green roofs:

• Conserve energy
• Improve the lifespan of roofs
• Provide sustainable urban drainage, thereby reducing flooding
• Provide a shelter for wildlife
• Improve air quality
• Provide noise abatement
• Mitigate climate change.

Whilst green roofs come in many different forms and types, usually a distinction is made between intensive, extensive and biodiverse roofs.

As a result of Living Roofs and Walls: Technical Report Supporting London Plan ^(PDF-2580K) the first direct policy in the delivery of green roofs in the UK has been released in the UK. The policy stipulates that The Mayor will incorporate living roofs and walls wherever feasible.

Further information on worldwide green roof policies can be obtained from Living roofs and guidance on planning, design, construction and maintenance of green roofs can be obtained from CIRIA – Building greener.

Glossary

Intensive roofs

These are composed of deep substrates of over 20cm in depth and can support a wide range of plants and vegetation type. They are generally heavy and require a large amount of support from the building.

Extensive roofs

These are composed of lightweight layers of free-draining substrates that support drought tolerant plants. The depth can be only a few millimetres with a maximum of 10-15cm. These roofs have a potential for wide spread use due to needing a lack of support from the building.

Biodiverse roofs

These are designed to replicate a habitat for a specific species, or to create habitats that maximise the number of species that can inhabit and use the roof.