Friday 6 September 2019

How to build a climate-proof home that never floods

The Netherlands has found an ingenious way to combat rising water – build housing that does the same

Could climate change-resistant homes help solve the housing crisis? The Met Office’s conclusion was unequivocal. There is “no doubt” climate change played a role in the record-breaking temperatures that fried the UK and northern Europe last month.

But there was an irony in this year’s latest heatwave too. The scorching heat that sparked fears of buckled train tracks and made many of us yearn for rain was a symptom of a gradual shift that isn’t just raising temperatures but is making flooding more likely too.

The UK Climate Projections 2018 warn that coming decades would see a triple whammy of rising summer temperatures, rising sea levels and more extreme weather such as flash floods. In time, these patterns will fundamentally change where we live and the homes we live in.

Many of us already face an uncomfortably high risk of flooding. More than one in 10 of the new homes built in England in 2016-17 are in areas the Environment Agency deems at risk of flooding (it estimates they face at least a 1% chance of flooding every year). Over time, those aren’t great odds.

Yet the agency recently warned that “we can’t win a war against water by building away climate change with infinitely high flood defences”. Instead it is calling for housebuilders to construct homes that are more flood-resistant, for example by adding watertight flood doors and thicker, more waterproof membranes in the walls.

This sort of technology is getting better. Much of it comes from the Netherlands, where they know a thing or two about flood defences.

There are also things that can be done to make homes more resilient in the event that the worst happens, and flood waters do get in.

 Schoonschip, a floating home project in Amsterdam. Photograph: Isabel Nabuurs
As anyone who has endured the horror of a flooded home will tell you, one of the biggest expenses in the aftermath is replacing waterlogged wooden flooring and joists and sodden electrics.

Housebuilders can mitigate these risks fairly easily, by installing concrete floors and routing power cables as high as possible.

In the long term, such building techniques will become increasingly mainstream. By the 2080s up to 1.5m homes in England will be in areas at significant risk of flooding, according to the Committee on Climate Change.

But a more radical change to the way we build homes could deliver a more immediate benefit – by helping tackle the housing crisis.

Building homes that aren’t just resistant but immune to flooding could allow developers to build safely on land currently dismissed as unviable because it has a high flood risk.

Opening up swaths of extra land for development, especially in the most densely populated parts of the country, might even give developers a fighting chance of meeting the government’s target of building 300,000 new homes a year.

The most tried and tested way to build in flood-risk areas is to lift the house off the ground. Humans have been building homes on stilts for millennia, and this technique is still popular in south-east Asia, Central America and Brazil.

More modern techniques include building on a raised platform like a beach house – a familiar sight in my wife’s native Australia – or simply on banks of earth or concrete. Of course this approach requires an element of second guessing: you need to build the accommodation above the level any floodwater will reach.

But the latest technology solves this problem: houses that float and rise with the floodwaters.

Ingenious Dutch architects – where else? – have designed houses that have a buoyant, air-filled concrete base instead of conventional foundations anchoring them to the ground.

Some are intended to float full-time and are bound together to form floating communities that sit atop the water of a lake.

Others are amphibious, designed to sit on terra ferma most of the time but able to float safely in the event of flooding, albeit with copious moorings to prevent any relocation.

Such technology comes at a price. Amphibious houses cost about 20% more to build than a conventional design. With prices falling in some parts of the country and builders seeing their margins squeezed, persuading them to build more expensive homes won’t be easy. The clincher could be the land question.

A combination of strict planning rules and “landbanking” – developers’ habit of buying but not building on land – is driving up prices in many parts of the UK.

By contrast, floodplain land is cheap. So technology that enables homes to be built safely in areas that were previously off limits could make business sense for private developers and spur the construction of thousands of affordable, unfloodable homes.

Other parts of the property industry would need to get, ahem, on board. Insurers will want to be sure of the houses’ immunity to flooding, as will mortgage lenders. But both serve conventional homes in flood-risk areas, so there’s no reason for them to eschew homes that cannot flood, no matter how high the water rises.

This won’t magically solve the housing crisis or eliminate all flooding risk. As climate change steadily puts more conventional homes at flood risk – whether from tidal surges, or rivers and drains overflowing – the UK needs to continue investing in flood defences.

But if we’re willing to embrace the new technology of floating and amphibious houses, we can unlock tracts of cheap floodplain land that could be used for some of the new homes Britain needs so desperately.

As the Environment Agency says, we can’t out-build the flood risks of climate change. But if we’re canny, we might just turn some of the threat into an opportunity.

(Source: The Guardian)

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