Wildflower Extensive Green Roof Systems
A Wildflower Extensive Green Roof is a green roof designed to support hardy vegetation, specifically native wildflowers, grasses, and sometimes sedums, on a shallow growing substrate. It delivers strong biodiversity and sustainability benefits while requiring minimal ongoing care.
Sika® NatureRoof Wildflower Extensive Green Roof Systems
Sika® NatureRoof Wildflower Extensive Green Roof systems replicate the aesthetics and biodiversity benefits of a ground level wildflower meadow at roof level, have a long flowering window and are compliant with building regulations fire performance requirements (BRoof(T4) and the GRO Code of Best Practice.
Key System Features
- Dry weight: 100 kg/m²
- Saturated weight: 154 kg/m²
- Build-up: 144 mm
- Rainfall retention: 55–65%, storage up to 40 l/m²
- Suitable for roofs: up to 45° pitch
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A Sika® NatureRoof Wildflower Extensive Green Roof system will typically have a dry weight of 100 kg/m2 and a saturated weight of 154 kg/m2 with an overall build-up height of 144 mm above the roof system. These weights reflect a Sika® NatureRoof Wildflower Extensive Green Roof system that is installed with a level low organic material growing medium, to a minimum settled depth of 100 mm over a 40 mm deep water retention and drainage layer with filter fleece.
Planting is commonly achieved using either Wildflower and Sedum Plug plants that are available in a variety of species to provide greater plant diversity and flexibility for shaded or sunny areas, or through the casting of Wildflower seeds which are available in a variety of seed mix options. Pregrown Wildflower blankets with a minimum 75% plant cover are also available for more instant plant cover. Wildflower and Sedum plugs, or Wildflower seeds, will take 12 to 18 months to achieve circa 60% to 70% plant cover with full cover taking up to 4 years.
Suitable for flat roofs and zero falls’ roofs Sika® NatureRoof Wildflower 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 Wildflower 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 Wildflower Extensive Green Roof systems provide positive contribution to rainfall management, retaining approx. 55% - 65% of rainfall depending on saturation level and up to 40 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 Wildflower Extensive Green Roof systems should be maintained twice annually, at a minimum, in the Autumn and early Spring. This should also include cutting back to a low level to support new growth and spread seed heads, creating a self-sustaining plant community. All grass cuttings and other organic matter must be removed to ensure increased fire load fire risk at roof level over time. Unwanted plant species such as grasses, buddleia etc. should also be removed.
Solar PV panels can be incorporated within a Sika® NatureRoof Wildflower 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 installed by Sika® SolarRoof Registered Contractors.
Sika® NatureRoof Wildflower 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
Wildflower Extensive Green Roof Systems - FAQs
No, Wildflower Green Roofs will flower from Spring to Autumn depending on the species mix.
Wildflowers require a deeper substrate than a Sedum roof to allow the root systems to support the increased plant height.
Only if not maintained properly through the removal of dead plant matter annually, the cutting of which also spreads the seed heads.
The deeper drainage board provides greater attenuation of water, which supports the Wildflower plant growth.
Pre-grown blankets are planted in a nursery field annually, and like the plants in a garden, grow with the seasons. Each year they will be dormant through the Winter.
