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.
Dry and Saturated Weights
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.
Plant Coverage
Planting can be achieved through forceable planting or by leaving the exposed growing medium to be pollinated naturally by airborne seeds. Forceable planting can be achieved using Plug Plants, shrubs and/or seeds, with planting normally chosen to meet the requirements set by an ecologist.
Roof Types and Installation
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 Roofs 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.
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Biodiverse Green Roof Rainfall Management
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.
Maintenance
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.
Biodiverse Green Roof with Solar PV Panels
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).