Traditional rainwater disposal systems are intended to remove water quickly, being designed to cope with the high intensity (high flow rates) that result from short duration storms.  Blue roofs manage the discharge of rainwater from roofs and podiums at a controlled rate, in line with an approved flood risk assessment and /or drainage strategy for a building or development.  

They are designed specifically to manage the rainwater, slowing its discharge into the drainage system and downstream infrastructure and are often coupled with other SuDS, biodiversity and ameniety elemets.

This reduction in flow rate helps protect the downstream environment from increased local flood risk, potential erosion, and pollution of watercourses.  

Although many blue roof suppliers have excellent technical support departments, they will always be restricted to offering their own products and methods.

By using an independant consultant, the methods and components selected will be those best suited to the application and project.  Watershed can also prepare a Tender specification which will enable the most competative cost whilst ensuring critical design elements are maintained.

Also, suppliers will limit their input and responsibility leaving the potential for scope and liability gaps, potetially embedding risk into the project.

Take a look at some design watchpoints here.

Watershed Engineering use their experience as Building Services Engineers specialising in Public Health and Blue Roofs to ensure that the blue roof is detailed as an integral part of the building services systems and that is effectively intergrated with the architecutural and structural engineering schemes.

We were sucessful in being awarded the CIRIA reseach project into blue roofs and are lead authors for their forthcoming guidance on the delivery of blue roofs.

Carl Harrop's article in the CIBSE Journal was seen by many as the catalyst for the increasing uptake of the method of rainwater sttenuation.

We are independant consulting engineers and as such are free to specify any approach we feel is right for a project.

We have also been innovative in developing new elelements such as inline downstream flow controls.

Peer reviews and design audits are a regular part of our work.

This can give clients and specifiers peace of mind that their system is effective and does not embed unecessary risk into the project.