Adrian Corrigall’s self-built house is part film set, part adventure playground – but all concrete. Tony Whitehead explores the ‘disruptive’ technologies behind a unique dream home
Even by the standards of Channel Four’s Grand Designs, the house built by deep-sea diver Adrian Corrigall was, to say the least, unusual.
Nobody else, even on a programme that showcases the ambitions of mavericks and outliers, had ever tried to construct a home entirely from rough-finish, exposed, in-situ concrete. The result attracted an enormous amount of media interest. Even now, two years on, internet opinion rages as to whether the house is a triumph or a monstrosity. Presenter Kevin McCloud plans to revisit the project for a ‘what happened next’ episode; meanwhile, Corrigall and his wife Megan are fielding calls from filmmakers wanting to use their extraordinary home as a set.
But the East Sussex house is at least as interesting for the technology it contains as for its uncompromising design. It contains no fewer than five different concrete mixes – the result of Adrian’s desire to create his dream home with the help of disruptive technologies. The formwork, too, was cutting edge: reusable and made from recyclable plastic (see box, below). It was as a skateboarding teenager that Adrian discovered a fascination with concrete: “I loved the shapes and textures of the skateboard park,” he says, “the way you could see, just by looking, how it had been made, how it had been poured into existence.”
This interest matured into a keen appreciation of concrete architecture, including the work of Louis Kahn, Peter Zumthor and John Lautner, designer of the futuristic concrete villa that features in the Bond film, Diamonds are Forever. “These guys were adventurous,” says Corrigall. “They were optimistic, pushing the boundaries and creating exciting stuff. That’s what I wanted to do too.” It was the boundary-pushing that led Corrigall and his architect, Graeme Laughlan of Raw Architecture Workshop, to Switzerland and the laboratories of Cemex Research Group. By allowing Cemex to showcase innovative products in his design, Corrigall won both concrete and expertise at favourable rates.
“Adrian wanted to over-achieve on cost,” explains Laughlan. “So when Cemex proposed mixes which could reduce or even remove the need for rebar, we were immediately interested. It not only cuts the cost of the reinforcement itself, but also the labour costs of fixing it and the need for a crane on site to place it.” Corrigall’s concrete home may be a small building by commercial standards, but at 260m2 it is a large house and technically quite demanding. And though a bungalow, it does in fact contain seven levels. The entrance is 1.2m below ground, and this rises through a series of steps to the sleeping quarters which are at a similar level above ground.
A house made from rough exposed concrete might be an interesting idea, but what is it really like to live in? Having occupied his unusual home for more than two years now, does self-builder Adrian Corrigall have any regrets about his adventure to the extremes of residential architecture?
“Absolutely not,” he says. “I really love it. I think people got the wrong idea about the house when they saw it on television. The cameras were there when it was still really a building site. There were grout runs and wet stains. It’s not like that any more. When it’s fully dried, the concrete calms down and the look becomes … I call it ‘considered imperfection’.”
Corrigall is constantly amused by the way his home confounds the expectations of visitors: “It’s odd, people actually think it’s going to be cold and damp. Why would I live in a house like that? In fact, the thermal mass of the exposed concrete retains heat really well and the insulation works brilliantly. In two years we have only used the heating once – and that was this winter after a period of sustained freezing weather. The previous winter we only needed our NVHR [natural ventilation and heat recycling unit].”
The thermal mass effect is only one of several ways the Concrete House performs well environmentally. “One of the advantages of pouring a house is that it’s naturally very airtight,” says Corrigall. “We pressure-tested it and it’s near Passivhaus standard. It’s great, too, that the formwork was reusable as well as being made from 100% recyclable plastic. And my house will easily last a lot longer than the average new home being built today – potentially for centuries.”
The house’s final surprise is the way it behaves acoustically: “It is not at all echoey as people expect,” says Corrigall. “The solidity of the walls, and the roughness of the surfaces, seem to dampen rather than reflect noise. And when you find it’s acoustically how you wanted it to be, just how you planned it, that’s fantastic.”
Architect Graeme Laughlan agrees, describing the acoustics as “almost monastic – it’s a house to pad about in”, and an object lesson in how exposed concrete’s reputation for echoes is at least partly due to its usual deployment in larger, more open-plan buildings.
“We wanted the house to be an adventure,” explains Laughlan. “So as you move through, there are these changing floor levels, changing ceiling heights, and changing light levels. In the darker areas you see light coming round the corner from lighter spaces. You want to explore.” Cemex proposed its proprietary fibre-reinforced concrete for the floor and roof slabs – a mix which potentially requires no reinforcement at all.
But local conditions prevented this, explains structural engineer Adam Redgrove, director at engineersHRW. “The ground was clay with potential for heave, so we specified trench footings of standard concrete, mainly under the walls, and the slab spanned some 3.5m between these. The span meant we had to have a reinforcement mat, but because of the extra strength provided by the fibre reinforcement we were able to reduce it to one mat rather than the usual two. We did the same for the roof slabs.”
Around 120m3 of fibre-reinforced concrete was supplied to form the ground slabs and the upstands between level changes. Once this had been poured, it was time to deploy another specialist concrete, a proprietary thermal insulating mix called Insularis. “There was concern over the thermal performance at the joints between the slab and the walls, and the walls and the roof,” says Laughlan. “So the walls sit on kickers made from Insularis. We looked at prefabbing this element, but in the event it was all done in situ with Insularis.”
This concrete gets its insulating qualities from a blend of 8mm coarse and 1mm fine lightweight aggregate, but the mix is unusual and initially caused the pump to block. Channel Four’s cameras captured the tense moments when site workers struggled to fill the forms with shovels and wheelbarrows before the concrete went off. Fortunately, the kickers are only 175mm high, and were successfully constructed. When the time came to deploy more of the insulating concrete, at the junctions between the walls and ceilings, adjustments to the mix allowed it to be to pump-placed without mishap.
But perhaps the most unusual feature of the construction are the walls themselves. “These don’t have any reinforcement at all except for a single line of connecting rods that run from the slab through the kickers,” says Laughlan. “They comprise a slender outer skin just 100mm thick, 150mm of insulation and a 125mm-thick inner skin.” While the thinness of these sandwich layers was in part facilitated by the lack of reinforcement, and the obviated need for cover, it is also extraordinary that concrete walls several metres high can be structurally sound and yet so slender.
The secret of course is in the mix, as Richard Kershaw, national technical manager with Cemex UK, explains. “Like the Resilia Conventional we used for the slabs, the Resilia HP [High Performance] we supplied for the walls contains a mixture of steel fibres and glass fibres of different lengths. The proportions of steel and glass, together with the different lengths of fibres used, are key to the products’ strength.”
Adrian Corrigall discovered Peri Duo formwork in 2017 at its UK Concrete Show launch. The system comprises plastic forms and formliners locked together by integrated levers and, since each form weighs no more than 25kg, Duo can be used without the need for a crane.
Each Duo panel typically measures 900mm x 1,100mm, and three lorryloads, amounting to 355 panels, were used to construct the entire building. The panels can be used horizontally or vertically, up to 35 times. All walls were completed in 29 pours, with pour heights varying from 2.3m to 3.8m. ALPHA props provided direct support for 345m2 of concrete slabs, which were completed in five pours.
Originally designed with small projects and developing countries in mind, the Duo formwork requires relatively little expertise to use. The plastic formliners are easily replaced and striking simply involves loosening the levers and pulling hard. “Adrian and Megan basically just ripped the forms down whenever they had time,” says architect Graeme Laughlan. “It meant the curing times were not as consistent as they might have been. Nevertheless, I think the Duo system is a good one and I’d be happy to use it on other projects.” Though Duo is simple to erect and strike, Peri used augmented reality software and produced drawings in 3D to facilitate the design stage. This was particularly important at the Concrete House as, due to its fluidity, the self-compacting concrete mix exerts a higher pressure than conventional concrete. Panels were limited to a maximum pressure of 50 kN/m2.
Despite the sophistication of the design approach, it was not proof against site slip-ups. While Channel Four’s cameras were filming, an incorrectly secured Duo panel caused the formwork to rupture on one pour, and the wall section involved had to be remade. The embarrassing error does not seem to have harmed the Duo brand: it has since been used on a variety of residential schemes worldwide, including projects in Brazil, Singapore and India.
For the high-performance mix, they used a higher dosage of fibres, the details of which must remain confidential, he adds. “The trick is to use exactly the right amount of paste in combination with just the right aggregate size to keep the fibres suspended and well distributed. Get this wrong and you risk the fibres ‘dropping out’.”
Since the high-performance mix was self-compacting, it was also highly ductile, allowing it to be poured into slim forms with no need for vibration. Pouring the walls was not without its share of drama, however. When one delivery vehicle suffered a puncture, the resulting delay in getting the mix to site caused a pour-line along an external courtyard wall. Fortunately, the high-performance mix had four hours of consistence retention, so the material was able to be placed after the short delay with only an aesthetic line on the wall.
Once structurally complete, one more specialist mix was needed to finish the floors. These featured underfloor heating pipes to be laid beneath a finished screed. A bespoke version of a proprietary self-compacting concrete was designed to allow a power-floated finish. The mix contained a maximum 6mm aggregate (smaller than usual) to allow for thin, smooth layering, and a range of admixtures provided a two-hour flow retention to allow the contractor time to work with the material.
Aesthetically, Corrigall’s house will always have detractors: Kevin McCloud is among those who have voiced doubts about its raw design. Few would dispute, though, that its use of “disruptive” construction techniques has been a success. Some of the technology involved has already found its way into other developments. Indeed, Resilia was recently specified for a boutique residential project in London designed by 1200 Works – an architectural practice founded by one Hugo McCloud, Kevin’s son.