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    Exploring the Benefits and Design Principles of Blue Roofs

    August 2023


As sustainable building practices continue to gain momentum, innovative solutions are emerging to address urbanisation challenges, water management, and energy conservation.

One such solution is the blue roof, an ecologically conscious approach that not only enhances a building's environmental footprint but also ensures effective water attenuation.

In this short technical article, we look into the intricacies of blue roofs, their benefits, and the design principles required to align with industry standards such as BS 6229: 2018 and the NFRC Technical Guidance Note for Construction and Design of Blue Roofs. Please note however, that the information provided is intended for information purposes only and is not exhaustive. For specific project requirements, please contact us at Proteus Waterproofing.

What is a blue roof?

A blue roof is a sustainable construction feature designed to mitigate stormwater runoff, reduce flooding, and promote water conservation. Unlike traditional roofs that simply shed water, blue roofs provide controlled temporary water attenuation, imitating natural water retention and percolation processes. This controlled release of rainwater offers multiple advantages, including flood control, reduced strain on drainage systems, and enhanced green infrastructure.

Benefits of a Blue Roof

Blue roofs act as on-site reservoirs, temporarily storing rainwater and releasing it gradually into drainage systems. This prevents sudden and excessive surges of water that can lead to flooding and erosion.

By managing stormwater runoff, blue roofs contribute significantly to flood prevention, especially in densely populated urban areas where impervious surfaces dominate the landscape. The controlled release of rainwater from blue roofs also promotes water conservation by reusing rainwater for irrigation or other non-potable purposes.

The thermal mass of water in blue roofs can contribute to regulating indoor temperatures, reducing the building's energy demand for heating and cooling. Blue roofs can also be designed as green roofs, supporting vegetation that enhances urban biodiversity, air quality, and aesthetics.

Design Principles and Standards

A crucial aspect of blue roof design is a certified waterproofing system, such as those supplied by Proteus Waterproofing and endorsed by us as suitable for blue sustainable roof applications. Such waterproofing layer(s) prevent water ingress into the building while allowing controlled water attenuation. All waterproofing supplied by Proteus is BBA certified to ensure compliance with material standards and relevant codes of practice.

Water Discharge and Attenuation

Blue roofs feature specific flow restrictor outlets to meet the required water discharge rate, accessible for inspection and maintenance. These roofs are designed to fully drain over the designated retention period. Permanent water retention on the waterproofing layer is avoided, aligning with industry best practices.

Overflow Mechanisms

To avoid water ingress into the building during extreme weather conditions, blue roofs incorporate overflow mechanisms independent of the rainwater drainage system. These overflows provide a visible warning of potential drainage blockages, ensuring effective water management.

Insulation and Thermal Considerations

Designing blue roofs as warm roofs or inverted warm roofs involves careful consideration of insulation. In the case of inverted warm roofs, additional insulation compensates for the cooling effect of water penetrating the insulation and reaching the waterproofing layer, following the guidance in BS 6229.

Waterproofing and Drainage Layer (WFRL)

The Waterproofing and Drainage Layer (WFRL) is a pivotal element that ensures effective water management and minimises water penetration to the insulation layer. It's lapped and sealed to prevent rainwater from infiltrating below the insulation layer. The WFRL is also lapped and taped onto the lip of the water attenuation chamber, providing a secure water drainage path.

Protrusions and Penetrations

Attention is paid to limiting penetrations of the waterproofing layer, restricted to rainwater outlets and overflows. Protrusions and penetrations, including those between insulation and the water attenuation chamber should be sealed meticulously to maintain the integrity of the system.

Topping and Flotation Prevention

To prevent insulation flotation, blue roofs incorporate sufficient topping of ballast, paving, or green roofing materials. This ensures that flotation forces are effectively counteracted and that the system remains stable under varying water levels.


As the construction industry continues to prioritise sustainable practices, blue roofs stand out as an innovative solution that effectively addresses stormwater management, flood control and water conservation. Designed in accordance with standards such as BS 6229: 2018 and the NFRC Technical Guidance Note, blue roofs combine cutting-edge technology with environmentally conscious principles to create buildings that harmonise with their surroundings while contributing positively to urban resilience.

With certified waterproofing systems such as those supplied by Proteus, meticulous design, and careful attention to thermal and drainage considerations, blue roofs are a noteworthy advancement in sustainable building design.

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