Blue roofs are becoming a common approach to manage local flood risk and attenuate water. But what are they?
Traditional flat roof drainage design principles state that all rainwater should be removed from the roof as quickly as possible. However, rainwater management within urban areas is becoming more critical due to the effects of climate change increasing the risk of flooding within our communities. As these effects become more apparent, this traditional drainage design method is increasingly being challenged.
As defined within BS 6229:2018 Flat roofs with continuously supported flexible waterproof coverings – Code of Practice, a blue roof is a “roof designed to attenuate the rate at which rainwater is drained from the roof and is allowed to enter the drainage system”. A blue roof is not rainwater storage on a roof.
A blue roof provides source control, managing rainfall where it falls by temporarily attenuating it on a roof. It mimics the natural environment by managing the discharge of rainwater from roofs at a controlled rate in line with a drainage strategy and overall site flood risk assessment. They are becoming a common approach to deliver Sustainable Drainage Systems (SuDS) and manage local flood risk, particularly in dense urban environments where space is at a premium.