Blue Roof Crates - Modular SuDS Attenuation Crate System (UK)

Frequently asked questions

What are blue roof crates?

Blue roof crates are modular HDPE attenuation units laid above a waterproof membrane on a flat roof. They create a shallow void that stores rainwater during a storm and releases it slowly through a flow-control outlet - turning the roof itself into a SuDS attenuation tank without using any ground space.

Do you supply blue roof crates UK-wide?

Yes. The Green Roofer supplies blue roof crate systems across mainland UK on standard pallet courier, with technical specification support, flow-control outlet sizing and CAD details for tender packages.

Can blue roof crates be retrofitted to an existing flat roof?

Yes - provided the existing waterproof membrane is sound and the deck can carry the additional saturated load (typically 90–160 kg/m² depending on storage depth). We always recommend a structural and membrane check before retrofit.

Can a blue roof crate system be combined with a green roof?

Yes. A blue-green roof places a sedum or biodiverse build-up directly above the crate field - you get SuDS attenuation plus full biodiversity, U-value and amenity benefits in a single roof zone. This is now the preferred spec for many London Plan and BNG-conditioned developments.

How is the discharge rate controlled?

A calibrated flow-control outlet - either a fixed orifice plate or a vortex flow controller - is fitted at the roof outlet and sized to match the planning discharge rate (commonly greenfield run-off, e.g. 2–5 l/s/ha). Water held in the crate field above this rate is released slowly over hours.

How much do blue roof crates cost?

Pricing depends on roof area, storage depth required, flow-control specification, top finish and delivery location. Send us your project details - roof area, planning discharge rate and any green roof finish - and we'll come back with a fixed supply-only quote.

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.