Biodiverse Green Roof Systems
A biodiverse green roof - also known as a brown roof - is a type of extensive green roof specifically designed to create and support habitats for wildlife, often mimicking or replacing the natural ecosystems lost during building development. They are intentionally designed to attract and support wildlife, including insects, birds, and other species and often aim to recreate habitats lost during construction.
Sika® NatureRoof Biodiverse Extensive Green Roof Systems
Sika® NatureRoof Biodiverse Extensive Green Roof systems provide the greatest opportunity for the creation, replication or reinstatement of the most biodiverse habitats at roof level, particularly within an urban environment. Elements such as bug and insect hotels, lying logs and ponding water can be incorporated, as can sand bars and large stones and boulders.
Key System Features
- Dry weight: 82 kg/m² - 143 kg/m²
- Saturated weight: 128 kg/m² - 215 kg/m²
- Build-up: 124 mm - 194 mm
- Rainfall retention: 60–70%, storage up to 50 l/m²
- Suitable for: Roofs up to 45° pitch
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Installed with an undulating and/or mounded low organic material growing medium, settled depth is typically between 80 mm and 150 mm but can be deeper. Beneath the growing medium is a 40 mm deep water retention and drainage layer with filter fleece. A Sika® NatureRoof Biodiverse Extensive Green Roof system will typically have a dry weight of between 82 kg/m2 and 143 kg/m2, a saturated weight of between 128 kg/m2 and 215 kg/m2, with an overall build-up height of between 124 mm and 194 mm above the roof system.
Planting can be carried out either through direct planting or by allowing the exposed growing medium to be naturally pollinated by airborne seeds. Direct planting may involve the use of plug plants, shrubs, or seeds, with the chosen method typically guided by the specifications provided by an ecologist.
Suitable for flat roofs and zero falls’ roofs Sika® NatureRoof Biodiverse Extensive Green Roof systems can also be installed on roofs up to 45 degrees pitch, or on waived, curved or domed roofs. A Sika® NatureRoof Biodiverse Extensive Green Roof is installed on-site using individual components to create each layer. Green Roof systems should be installed by suitably qualified individuals holding LANTRA or GRO installation qualifications. When installed by a Sika® NatureRoof Registered Contractor the green roof system forms part of the comprehensive Sika roof guarantee.
Sika® NatureRoof Biodiverse Extensive Green Roof systems provide positive contribution to rainfall management, retaining approx. 60% - 70% of rainfall depending on saturation level and up to 50 l/m2 of permanent water storage. As this retained rainwater evapotranspirates, the green roof contributes to the cooling of the urban environment, as recognised by the House of Commons Environmental Audit Committee inquiry in 2024 into Heat resilience and sustainable cooling, which led to a recommendation that Government legislate for the use of green roofs in cities across the UK.
Sika® NatureRoof Biodiverse Extensive Green Roof systems should have a maintenance programme designed to support the specific planting of the individual roof areas, but be maintained at a minimum of once a year. Remove all unwanted plant species such as grasses, buddleia etc. and any organic matter that may increase fire load fire risk at roof level over time.
Solar PV panels can be incorporated within a Sika® NatureRoof Biodiverse Extensive Green Roof system creating a BioSolar system that is compliant with the requirement of the Department for Education (DfE) schools’ output specification. The inclusion of solar PV panels with the green roof enhances the power output of the PV system due to the evapotranspiration of moisture from the green roof. This cools the panels, whilst the green roof also reduces the solar gain experienced by traditional exposed waterproofing. Sika® NatureRoof PV Green Roof systems are designed in accordance with the GRO BioSolar Best Practice Guide with the solar panel systems being installed by Sika® Solar Roof Registered Contractors.
Sika® NatureRoof Biodiverse Extensive Green Roof systems can be installed over a Sika® RetentionRoof Blue Roof system for enhanced rainfall management contribution to a site-specific Sustainable Drainage System (SuDS).
System Components
Biodiverse Extensive Green Roof Systems - FAQs
Yes, Biodiverse Green Roofs can be designed to attract ground nesting birds such as the Black Redstart.
The growing medium for a Biodiverse Green Roof is laid in mounds or undulating to create habitat for invertebrates, arachnids, insects, beetles and birds. The uneven substrate will also capture airborne seeds.
The key principles for Biodiverse Green Roofs were developed by Dr Stephan Brenneisen of ZHAW Zurich University of Applied Sciences in Basel, Switzerland.
Logs are used on Biodiverse Green Roofs to create habitats for invertebrates, arachnids, insects and beetles.
