- Project plans
- Project activities
- Legislation and standards
- Industry context
Last edited 11 Apr 2019
A blue roof is a roof designed for the retention of rainwater above the waterproofing element of the roof. This is as opposed to more conventional roofs which allow for rainwater to drain from the roof.
Blue roofs are typically flat, without any fall, with control devices regulate drainage outlets that enable water to be retained or drained. They can be designed as open water surfaces, as storage within or beneath a porous or modular surface, or below a raised surface or covering.
Some of the reasons for incorporating a blue roof into a building, include:
- As a form of Sustainable Urban Drainage System (SuDS) to try and alleviate urban flooding caused by stormwater run-off.
- In areas of urban density, the space created by a blue roof can avoid having to provide attenuation for rainwater at ground level.
- Rainwater harvesting for use, independent from, or supplemental to the mains water supply, such as wc flushing or green roof irrigation
- Cooling solar panels, or reducing load on mechanical refrigeration or cooling equipment.
- For recreational purposes, such as rooftop swimming pools or water features.
Unlike some other forms of SuDS, blue roofs make use of spaces that might otherwise be redundant without extending beyond the footprint of the building or into ground space which, depending on the density of the location, may be expensive.
To ensure safety, there must be careful estimation of the flow restriction, which calculates the peak rates of run-off and the water depth that will be formed on the roof surface. This informs the design of the safety overflows, the preventative maintenance programme, and the design and construction of the waterproofing layer.
 Related articles on Designing Buildings Wiki
Featured articles and news
We have a great range of introductory articles written by ECA.
7 of the most common myths, busted.
Consider a career in the electrotechnical industry.
Exploring local assets of community significance. Book review.
Wood-burning stoves should not be used in thatch-roofed buildings.
Servitisation, smart systems and connectivity.
What happens to the Construction Products Regulation if there is no Brexit deal.
The first step to long-term prosperity.
The status and rights of employees in construction
Continuing to share environmental best practice.
The employee assistance programme EAP.