NFRC Technical Guidance Note for the construction and design of Blue Roofs. Roofs and podiums with controlled temporary water attenuation.

A Blue Roof is a Flat Roof, designed to allow controlled attenuation of rain fall during heavy and storm events as part of a Sustainable Urban Drainage Systems good practise policy, replicating the natural environment or improving the as built environment. A Blue Roof will treat and release the water at a managed and controlled rate directly into the sewers waterways and river systems.

In the absence of British or European standards for blue roof design and installation, this guidance was produced by a committee formed of the NFRC Joint Flat Roofing Technical Committee, whose members include, Membrane and System Manufacturers, Insulation Producers, Standards and Certification Bodies, Drainage Consultants and representatives from Flat Roofing trade associations. It aims to support the design of technically correct Blue Roof construction and provide information for specifiers, designers and installers.

The guide focuses purely on the ‘hard’ elements of the blue roof: the waterproofing, drainage and substrate, with no mention of a surface vegetation layer. However this type of roof can be capped with a layer of plants, as shown in the illustrations throughout the guide, to bring biodiversity benefits and act as a nature-based solution.