160 Old Street is a nine-storey office redevelopment scheme in London designed by Orms Architects on behalf of The Great Ropemaker Partnership, a 50/50 joint venture between Great Portland Estates plc and Ropemaker Properties Ltd. Formerly known as 148 Old Street and owned by Royal Mail, consent was awarded for the comprehensive refurbishment plans in 2015. Completed in 2018, the 14,920m 2 of office space comprises a complex array of 29 different roof zones over multiple floor levels, with 16 of the areas re-designated to blue roofs and or green/biodiverse roofs. This design encourages local biodiversity, and attenuates storm water at source to reduce the volume of surface water runoff and the associated risk of flash flooding. The blue roof option was deemed the most cost-effective SuDS solution for the restricted site, with the construction of a basement stormwater attenuation tank deemed impractical, prohibitively expensive and impacting plans for the majority of the basement to be converted into office accommodation.

For this reason, blue roofs were the preferred solution for SuDS compliance on the project. This is driven in part by climate change with more frequent and extreme rainfall events; as well as government planning policy which is encouraging rainwater runoff to be controlled as close to its source as possible. Increased awareness of the blue roof solution was being raised by key design guide documents, such as the National Flat Roofing Contractors Technical Guidance Note for Blue Roofs that sets out basic minimum performance criteria and includes advice on insulation, falls, waterproofing, exceedance overflows and surface finishes. More in-depth guidance on SuDS, including specific examples of dos and donts, is available in CIRIAs SuDS Manual.