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Roofing and flooding, can a roof be the answer?

Roofing and flooding, can a roof be the answer?

Despite assurances to the contrary, anyone observing the news over the last few months might easily conclude that the UK is unprepared to cope with extreme weather.

But the recent flooding wreaked upon us by storms Clara and Dennis, is not new. The Somerset levels seem to have been underwater for most of the last decade. And the areas worst affected by flooding now, saw the same or similar flooding last year.

Almost every region of the UK has seen flooding and suffered the consequences, including closed roads, railways and motorways, business disruption and thousands of people made homeless.

These changing weather patterns were predicted decades ago and talk now of future investment of £4 billion to introduce flood defences, is too late. Many of those flooded out of their homes for the second year running, were promised action last year.

5.1 million people live in areas at risk of flooding and the potential impacts are catastrophic. Economically flooding can cost over £100,000 per hour and 40% of businesses affected never re-open.

So what can the roofing industry in particular, do to help alleviate this problem?

Following the great storms of 1987 and 1990, the industry worked together to introduce new codes of practice around the mechanical fixing of roof slates. The British Standard was re-written and has been improved further since.

Whilst you wouldn’t normally associate roofs and roofing as a way to alleviate flooding, it can certainly have a big impact.

The primary role of a roof is to keep the interior of a building dry.

Most roofs are designed to shed water quickly into rainwater gutters, through downpipes, into the drainage system and into rivers. It’s a quick efficient process and due to the speed at which rainwater is diverted into them, this can cause flooding.

The use of soakaways has helped to reduce the burden on surface water drainage, but their use represents a drop in the ocean.

But, what they do highlight is that great improvements are most commonly achieved by a combination of small ‘marginal gains’, rather than one dramatic great leap forward

If we are able to slow down the rate at which water drains from roofs we can make a valuable contribution to help alleviate the enormous cost and misery the floods are causing.

Green roofs absorb large quantities of water. Any surplus to its requirements will be released slowly over several hours, during which time much also evaporates and the combined effects greatly reducing the flood risk.

Water harvesting system can further contribute. Forward looking clients and designers are using harvested rainwater to water their gardens, flush toilets and clean cars.

What a terrible waste it is to use drinking water for these purpose when, with a very little foresight, water can be gathered and used free of charge and without putting further burden on resources.

There are of course many other benefits from green roofs, including many financial ones.

Another roof related option is blue roof design. Similar to green roofs and often incorporating green roof elements,  blue roofs hold water on the roof,  attenuate the drainage and allow it to be released slowly.

In the past some asphalt roofs were designed to deliberately hold water; not for environmental reasons, but because it was thought that standing water would keep the roof cooler, protect the membranes and extend their life.

Of course both green and blue roofs do those things as well.

Blue roofs as a means of slowing water drainage is a relatively new idea and the NFRC have published a paper which is available here.

So next time you are watching the news and blaming inadequate politicians and civil servants, look at yourself. With your knowledge and influence, and our help, you may have the answer in your grasp.

Please do not hesitate to get in touch with us about these issues or any other commercial roofing projects you would like help with or for which you are looking for an excellent contractor