Last winter’s flooding saw thousands of people evacuated from their homes; some are still waiting to move back in. And while everybody hopes that this winter will be kinder, the risk of further flooding remains.

“I was talking to the Environment Agency last week and they are very concerned,” says Justin Meredith, managing director of Floodline Developments. “The water table is very high from last winter. The water has nowhere to go.”

Floodline’s technical director Faruk Pekbeken is even gloomier: he describes flooding as “the UK’s earthquake” waiting to happen.

Floodline, set up four years ago, is a developer and water management consultancy which is proposing a flood solution that has worked well in the Netherlands: amphibious houses. Designed literally to float when flooded, they are known in the trade as “can float” houses. But promoting the concept has been like trying to make water flow uphill.

Part of the problem, Meredith admits, is down to public perception. Flooding is never an interesting story in the media unless regions are in crisis. Projects can founder if they cross political or council boundaries. And many local authorities do not have the technical capability to understand and interpret their own flooding policies.

“There is a lot of misinterpretation of policy. But everything that we are proposing complies with current UK planning legislation,” he says. Now, after four years of intensive research and lobbying, Meredith believes that the concept could finally be commercially viable for the UK market. And the Burghfield Park scheme in Berkshire, due to go to planning next year, could be the first large-scale development of its kind: a series of 30 waterfront homes built around a 200-acre lake, with in-built buoyancy for extreme flooding conditions. A new sailing club and around 150 traditionally built houses, set on higher land, are included in the proposals.

Water management measures (Meredith doesn’t like using the term ‘flood management’) are an integral part of the scheme. The lake capacity would be enlarged to accommodate an additional million cubic metres of water fed into it via culverts which would be opened when the local drainage system was under pressure.

It is an imaginative solution that, as well as providing accommodation on land hitherto considered impossible to build on, could solve some ongoing issues for locals. Last year when the Thames burst its banks nearby, roads were inundated and local villages were flooded. Pekbeken remembers an unsettling sight: the floodwater was slowly rising around the surrounding streets but it was not draining into the lake, even though that stretch of water sat 2m below ground level.

The principle behind Floodline’s scheme is that the lake acts as a kind of pressure valve, absorbing the equivalent of 360 Olympic swimming pools of water channelled away from surrounding roads and houses. “You can’t get rid of the water, but you can control the speed of it. And if you replicated this [concept] in other places along the Thames, you could start to make a tangible difference. It’s when the water hits major conurbations that it’s often most constricted,” Meredith says.

Unsurprisingly, the proposals for Burghfield generated a fair amount of media coverage at public enquiry stage, and the reaction has been mixed. More media focus was given to the floating houses and ecological questions than the flood alleviation measures. But Pekbeken argues that the Burghfield Park scheme could give villages in the surrounding areas up to 50 years of protection against flooding.

“This would make a huge difference to their insurance bills,” he says, adding that an extra incentive for councils is that the cost of water management measures would be borne entirely by the developer. Floodline would recoup its costs through cheaper land prices – after all, the land has hitherto been considered unsuitable to build on.

If such schemes were replicated across flood-prone areas of the UK, Meredith believes that they could make a major contribution to regenerating areas of towns and cities susceptible to flooding.

At present, five million properties have been identified as at risk of flooding. But for this distant prospect to become reality, a more holistic and non-territorial approach from local authorities is required. The public needs to be educated on the wider benefits of schemes, and financiers need to reassess their attitude to risk. It’s an area where the government cliché of “joined up thinking” should really be applied.

At present, councils could show a reluctance to embrace schemes that only directly benefit authorities further downstream. Residents worry that enlarging lake capacity may increase flooding risk (“it’s exactly the opposite,” Meredith argues, “We would be giving the river space to breathe”). Then there is the challenge of the unknown: amphibious houses are well established in the Netherlands, but not well understood in the UK.

Until now, one of the major obstacles to getting a “can float” house built in the UK has been the reluctance of insurers and mortgage companies to accept the idea. This is an irony not lost of Meredith, as insurers take the biggest hammering whenever floods occur. But he is pleased that mortgage providers are now on board. A panel of insurance companies also supports the concept.

“We’ve had to do a lot of box-ticking and background research just to get to the starting line,” he adds.

While it has been waiting for progress on its own developments, Floodline has been providing consultancy services on other projects, most notably Premier Inn’s floating hotel in Hartlepool, which recently received planning permission. This hotel would be built to the same concept of a “can float” house, albeit based permanently in the water.

Floodline is also watching with interest developments at the Royal Dock in London where the Carillion Igloo Genesis consortium has been chosen to design and build Britain’s first floating village.

“We welcome more people coming into the market, because it demystifies the model,” Meredith says.

“The more case studies that we can collect for the Environment Agency the better,” Pekbeken adds.

But they emphasise that their concept will not open the floodgates to building on every stretch of sensitive land. Coastal areas may be considered, but they would have to be in sheltered areas such as harbours or locks. And areas of heavy flooding are unlikely to be suitable.

Floodline’s consultancy arm has advised several clients to drop non-viable schemes on floodplains, despite commercial pressure to push them through.

“It depends on the rate of flow [of the water],” Meredith says. “Nobody wants to live next to a fast-moving torrent, even if the building can withstand it.”

Instead he points to the experience of the residents of Maasbommel, a Dutch village that surrounds an artificial lake. As well as some floating homes, some residents live in amphibious houses which have only floated on a handful of occasions.

Pekbeken says that there is initially some excitement when the water is expected to rise. “The residents call their friends over and hold flood parties. They expect something big to happen, but there’s nothing to see. The houses moved by millimetres. It’s actually quite boring.”

Boring – but after the high drama and human misery of last winter, it’s a word that UK flood victims may be happy to embrace.

How does a “can float” house work?

For most of the time, “can float” houses will rest on dry land. They are only expected to become buoyant in severe weather conditions, which could be only once in several decades, or may not even happen within the life-time of the property.

“We are not reinventing the wheel with this concept. It’s tried and tested,” Meredith says. The base of a “can float” house is a watertight self-contained reinforced concrete basement, which acts as a flotation chamber when necessary, but ordinarily rests on piles. Pekbeken says that the base design uses a fairly standard concrete strength of 24kN/m². But the formula contains additives and specialist coatings for higher durability and water-tightness.

Prefabrication is a major principle of a “can float” house. The flotation chamber is likely to be cast in segments in a factory, and then assembled and joined on site. Equally the house above it will be of modular construction, a lighter solution than conventional brick and blocks and better for buoyancy.

“We can’t build the traditional routes because the buildings are too heavy. But using efficient and lighter products is a great marriage. We are likely to produce highquality buildings that meet high BREEAM scores,” Meredith says.

Although there is some flexibilty in the design, Pekbeken says that it will not be possible for residents to configure the core parts of the building. Stairs, for example, must remain close to the middle of the design, providing balance.

To meet UK insurance requirements, the basement of a “can float” house will not be habitable.

The houses, which will often be on the waterfront, will be approached via a ramp above ground level. All services, including sewage, water and power will connect to the house through a series of flexible polyethylene pipes which can stretch if the property needs to move. The utilities cluster is likely to be bundled under the entrance ramp.

However, Floodline is also considering an alternative design whereby the polyethylene pipes enter the house from beneath the basement.

The house would be connected to a “guide pile”, which will sit outside the main structure. This would ensure that the floating house only moved on a vertical plane, unable to stretch in any other direction.

At Burghfield, the houses have been designed to rise by up to 1m. In the Netherlands, where flooding conditions are more extreme, guide piles typically allow up to 5m of movement.

So far, Floodline has developed models for three or four bedroom houses and will be bringing forward two-bed and five-bed options in the near future.

The company has been working with British prefabrication firms who will be ready to start manufacturing as soon as planning approval is received. But he adds that Floodline is not exclusively partnering with particular suppliers. And contractors do not need to develop particular skills to create “can float” houses.

“If we get to the position where suppliers can’t supply what we need in time, we need to have the flexibility to react to that and to go elsewhere.” Pekbeken stresses that they want to work with UK contractors. “It’s very important that quality is maintained. We need British companies who understand British laws and climate,” he adds.

This article first appeared in the November 2014 issue of The Construction Index magazine. To read the full magazine online, click here.

To receive you own hard copy each month in traditional paper format, you can subscribe at http://www.theconstructionindex.co.uk/magazine#

Got a story? Email news@theconstructionindex.co.uk