Blue Roof Flashings, Edge Trims & Kerb Upstands

Frequently asked questions

How high does an edge trim need to be for a blue roof?

There is no single suitable height. The detail depends on the attenuation depth, finished roof build-up, maximum water level and required freeboard. Waterproofing upstands are typically at least 150 mm above the finished roof surface, but blue roof conditions may require a higher detail.

Do you install rooflight upstands?

Rooflight upstands can be included in the commercial roof package. Their structure, waterproofing and height must suit the rooflight specification, blue roof water levels and safe maintenance access.

About Blue Roofs

Blue Roofs supplies its own water retention crates and designs and installs blue roof systems for commercial projects across the UK, including Essex, Southend-on-Sea, Chelmsford and London. Our modular attenuation crates store storm water on the roof and release it via flow restrictors. We work with developers, contractors and building owners on commercial flat roofs and podium decks, subject to structural and drainage checks. See our water retention crates or our commercial blue roof services.

Our core services support our crates with blue roof installation, storm water attenuation and SuDS design and compliance. We also offer our own green roofs, which can be paired with our crates as blue-green roofs: the green roof sits on top, with filter fleece between it and the crates storing storm water underneath. The combined design must allow for the saturated green roof load plus stored water. Flow control devices regulate discharge to the drainage network. We supply blue roof materials UK-wide for trade and commercial projects, including our water retention crate systems and podium blue roof systems. Components include flow restrictor outlets, emergency overflow outlets, drainage boards, filter fleece, protection fleece and pebble ballast.

System selection depends on roof structure, load capacity, waterproofing, storage requirements and the agreed discharge rate. Stored water adds load: 1 mm of water over 1 m² equals 1 litre and adds 1 kg/m². Emergency overflows and accessible outlets are essential parts of the design. Our blue roof maintenance service helps keep outlets, flow controls and overflows clear and working as intended. Blue roofs temporarily store rainwater runoff and release it at a controlled rate as part of a site-wide SuDS strategy.

Planning a project? Read our planning drainage strategy guide and SuDS compliance guidance. For commercial buildings we also supply and fit rainwater hoppers and roof flashings and trims. Learn the basics in what is a blue roof, our storm water management guide, active vs passive blue roofs and our guide to the complementary roles of our blue roofs and green roofs. Explore blue roof supply and pairing our crates with our green roofs for your project.