Will blue roofs be the answer to Britain’s flooding problem?

Most will be quick to blame climate change, but with overwhelming evidence that increased rainfall is going to be a major feature of winter weather in the UK, action needs to be taken now.

Britain is depressingly a long way behind its continental neighbours when it comes to managing water and excess rainfall. German cities in particular are several years ahead of us in the number of green roofs that seem to feature on almost every building.

These impressive roofs slow up the release of rainwater, encourage plant growth, attract birds and insects, and generally make a positive impact on the environment. According to Proteus Waterproofing, green roofs come into their own when rain first begins to fall, significantly reducing excess rainwater overwhelming sewers and storm drains.

While green roofs make a significant contribution to managing excess rainwater, in isolation they are really just a metaphoric drop in the ocean, particularly in the UK. At this moment there are simply not enough of these structures to make a significant impact.

Government legislation would help to encourage building owners to go green, but even then, many of these existing flat roofs were not built to take the additional weight needed to accommodate plants, irrigation components and the other products needed, which is why suppliers such as Proteus Waterproofing are turning to a different solution – the blue roof.

There would of course still be weight restrictions with such projects – water by its very nature is heavy, and in layman’s terms, a blue roof is effectively the equivalent of an empty swimming pool. It fills up when it rains and slowly releases the water back into the sewage system, usually over a 24-hour period when drains are better able to cope.

This has become increasingly more important as town planners are restricting the amount of rainwater leaving a construction site via the drainage system. This can be limited to 5-10 litres per second per hectare, the flow rates are the same for regional greenfield sites as part of a sustainable drainage policy (SuDS).

As with green roofs, going blue usually requires a bespoke design which building owners and specifiers should first check with suppliers, such as Proteus, who will work closely with them to ensure that the roof complies and meets the demands dictated by SuDS.

This is particularly important as from the 6th April 2015, it became compulsory for sustainable urban drainage systems to be considered in local policies and decisions on planning applications relating to major developments. This is to ensure that systems for the management of water runoff are implemented, unless demonstrated to be inappropriate.

In the past, roofs were designed to allow water to run off as quickly as possible which is why a blue roof is somewhat of an enigma. It means if you are holding water on a roof, you have to be very sure that the waterproofing membrane you employ is up to the job.

To meet this challenge, Proteus Waterproofing has developed a blue roof build up system which incorporates Cold Melt®, a seamless, waterproofing membrane that’s BBA certified to last the lifetime of the substructure on which it is installed.

Its seamless finish means that there is nowhere water can escape through. This is imperative because egress of water from any part of the roof can spell disaster for the building structure below, and if you are holding back the equivalent of a small swimming pool, it would be a major problem.

Combine Cold Melt® with Proteus’ Pro-Living® components and you have a roof with blue roof certification that will last the design life of the structure on which it is built – so what’s not to like!

Proteus can offer advice and expertise to support your blue roof installation, no matter how large or small. Just give us a call.