Green Roof Substrate - Lightweight Growing Medium
Green roof substrate is not topsoil. It is an engineered mineral-based lightweight growing medium designed to stay free-draining for 40 plus years, resist compaction, hold enough water and nutrient to support extensive vegetation, and weigh roughly half of garden soil when saturated. We supply two BS 8616 compliant mixes - an extensive sedum substrate at 60 to 80 mm and a biodiverse substrate at 80 to 150 mm - in 850 kg bulk bags on pallet nationwide.
Engineered lightweight green roof substrate, BS 8616 compliant. Extensive and biodiverse mixes for sedum and wildflower roofs. UK supply in bulk bags on pallet.
Frequently asked questions
Can I use topsoil instead of green roof substrate?
No. Topsoil is too heavy when saturated, compacts over time and blocks drainage. Green roof substrate is an engineered mineral-based lightweight medium designed to stay free-draining for 40 plus years - garden soil will fail within a few seasons.
What depth of substrate do I need?
Sedum roofs need 60 to 80 mm of extensive substrate. Biodiverse wildflower roofs need 80 to 150 mm of biodiverse substrate to support deeper rooting and a wider species mix. Going shallower than these depths shortens vegetation life.
How heavy is a green roof substrate?
Our BS 8616 compliant lightweight substrate weighs roughly 45 kg/m² dry and 70 kg/m² saturated at 80 mm depth. That is roughly half the saturated weight of garden topsoil at the same depth.
How much green roof substrate do I need?
One 850 kg bulk bag covers approximately 9 m² at 80 mm depth or 6 m² at 120 mm depth. Tell us your roof area and design depth and we will calculate the bags needed.
About The Green Roofer
The Green Roofer designs, supplies and installs green roofs for homes, developers and commercial buildings across the UK, with strong coverage in Essex, Southend-on-Sea, Chelmsford and London. We work on everything from a single garden shed or extension to large commercial flat roofs. See our residential green roof services or our commercial roofing services.
Our systems include sedum roofs, biodiverse and wildflower roofs, intensive roof gardens, blue roofs for stormwater attenuation and bio-solar roofs that combine planting with solar panels. Smaller projects are welcome too, including a green roof for your shed. We also supply green roof materials UK-wide for trade customers and DIY projects: complete systems such as the certified sedum green roof system, traditional green roof system, biodiverse green roof system and lightweight biodiverse system, plus individual components including sedum mats, wildflower mats, green roof substrate, drainage board, filter fleece, protection fleece and decorative cobbles.
Every project starts with a free site survey and a clear, no-obligation quote. We check roof structure, load capacity, waterproofing and drainage before recommending a system, and we offer ongoing green roof maintenance so the planting stays healthy year after year. Green roofs help manage rainwater, improve insulation, extend the life of the waterproofing beneath them and support biodiversity, including Biodiversity Net Gain requirements on new developments.
Planning a project? Read our guide to green roof planning permission. For commercial buildings we also supply and fit rainwater hoppers and roof flashings and trims.
Call 01702 964002 or email hello@thegreenroofer.co.uk for a free, no-obligation quote.