What actually is a blue roof? A blue roof is an evolution of the existing green roof concept but has been specifically designed to store water and in particular rainfall.

The goal of a blue roof is to ensure that rather than allowing water to drain from the roof at the earliest possible stage, the blue roof will deliberately retain some or all of the water above the waterproofing membrane, either temporarily or over a longer period of time and then deposit the water through a designated channel, such as a drain outlet to an area that will cause less damage.

Where Can Blue Roofs Help?

There are 3 primary areas where the installation of a blue roof can prove to be beneficial

  1. Effective Storm Water Management– The excess water deposited during storms can play an obvious and significant role in flooding throughout many areas of the world. The installation of a blue roof can play a pivotal role as part of a SUDS (Sustainable Urban Drainage Systems) at roof level. This will help to reduce the impact of rainwater runoff as the flow can be controlled through specifically designed outlets and redirected to less harmful areas. 
  2. Rainwater Storage – With rainwater being precious in many countries, finding a way to store rainwater effectively has taken on greater importance than ever before. The installation of a blue roof to a property can play a key role in the storage of rainwater. The harvested water can also be redistributed for irrigation purposes.
  3. Reduced Energy Costs – Blue roofs are known for their cooling properties and as such, can actually help to reduce the energy bills for the property to which they have been installed.
  4. Cooling and Energy Consumption – There was a study on a cider factory in Frankfurt on the Possman Cider Factory and Storage Facility on a blue roof which was installed in 1990 and paid for itself in electricity costs for cooling within 3 years. Click here for more on that study.
An image of a blue roof
An image of a blue roof installation

Are There Any Associated Issues?

For all of their qualities, the storage of water above the waterproofing membrane in a blue roof also poses a number of potential risks which cannot be ignored and must be addressed.

The main areas of concern are as follows:

  • Structural Issues – There can be no escaping the fact that water is heavy. It is absolutely essential that the structure of the building and the roof is fully assessed for suitability before any type of installation can begin.
  • Damage To The Waterproofing Membrane – With a significant amount of water being stored in a blue roof, what would happen if the waterproofing membrane became damaged? It’s difficult not to use the word catastrophic with the amount of damage that could be caused if too much water is released through the roof.

Please Note – Whilst there are definitely concerns relating to the installation of a blue roof, due to the modular nature of the M-Tray®, the potential risks can be substantially reduced by utilising our innovative modular roofing option as part of a blue roof.

A close up image of work taking place to install a green roof in Hammersmith
For more on the M-Tray®, please click here


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Wallbarn Ltd. Unit 16, Capital Business Centre,
22 Carlton Road, South Croydon.CR2 0BS