This paper reviews the devices suitable for building scale application and then outlines three case studies, two from Coventry, UK and one from Valencia, Spain. The first assesses the potential to retrofit an extensive green roof to the Frederick Lanchester Library, Coventry University. Costings are given, the structural strength of the building is investigated and various benefits of its installation, including potential to sequester and store carbon, are assessed. The second reports part of the AQUAVAL Project, Spain, whereby an extensive green roof was retrofitted to half of a school roof and porous concrete retrofitted to a pavement. Preliminary monitoring results show expected benefits, including attenuation of the storm peak and increased time to peak. The third case study using WinDes® software compared a conventionally drained new-build housing estate with a Sustainable Drainage Systems train of porous paving, bioretention and swales. Stormwater volume was reduced by ∼20% and peak flow by >250 L s–1. Addition of extensive green roofs to all buildings increased these differences and delayed return to baseflow conditions reflecting water stored in the management train components.