Blue Roofing

A blue roof system is a type of flat or low‑slope roofing design that temporarily stores rainwater on the roof and releases it slowly to help manage stormwater runoff. Unlike traditional roofs that drain water immediately, blue roofs use controlled drainage — such as flow restrictors, trays, modified drains, or passive ponding — to attenuate (slow down) water flow and reduce pressure on urban drainage systems.
 

Sika® RetentionRoof Blue Roof Systems can be integrated within a Sika® NatureRoof Green Roof, a Sika® NatureRoof PV BioSolar system or beneath a variety of permeable hard landscaping pedestrian surfaces.

Designed to contribute to, or provide the SuDS design requirements on a site, each roof is designed individually to help meet planning restrictions placed on the development, such as a limited discharge consent through the attenuation of rainfall as it falls on the roof.

The Sika® RetentionRoof Blue Roof will attenuate incident rainfall within the roof build-up whilst reducing the discharge of stormwater through a restricted flow-control device over the rainwater outlet.  This will limit discharge from the roof whilst other hard landscaped surrounding areas are drained.  The Sika® RetentionRoof Blue Roof will gradually discharge water from the roof after a storm event at the controlled rate over a set period, typically up to 48 hours.

Rainwater outlets not fitted with restricted flow-control will be utilised as overflow devices, enabling the roof to drain faster at the point of maximum capacity (known as ‘H Max’). 

Blue Roof’s are required as part of the London Plan since 2021 and are being introduced as planning requirements in other parts of the United Kingdom due to their positive contribution to rainwater management and flood risk alleviation.

When specifying a Blue Roof it is critical to ensure the waterproofing system used in either a Warm Roof or an Inverted Warm Roof installation has the appropriate BBA Certification.  Your local Sika® Area Technical Manager can advise on the correct SikaShield® 2 Layer Reinforced Bitumen Membrane or SikaShield® Hot Melt specification.