3D printing a two-storey home

“We printed the entire envelope in one piece, on site, in three weeks”

After 20 years working in building control, civil engineer Marijke Aerts thought it was time to do something a bit different: “In particular, I wanted to help construction become more sustainable through the use of transformative technology,” she says.

As it turned out, her career change proved dramatic. As project manager for Kamp C, a centre for innovation in construction in Belgium, Aerts (pictured below) has just overseen the construction of Europe’s first two-storey printed concrete house.“This is not printing components for assembly on site,” explains Aerts. “We printed the entire building envelope in one piece, on site, in just three weeks.”

Kamp C constructed the 8m-tall house using Europe’s largest concrete printer – a fixed gantry system device made by COBOD. “You erect it in just one day, like a crane,” says Aerts. “Working with printed concrete is a completely different way of building. There’s been a lot to learn, but it’s exciting work.”

The construction of the cavity walls is ingenious: an external layer comprises an outer skin some 40mm thick supported by a zig-zag inner skin to provide structural strength and stiffness. The inner layer of the wall is made in the same way and the 160mm gap between the two zig-zags is filled with insulation.

Operating the machine is the easy part: “The printer will put concrete exactly where you want it, when you want it.” More challenging, she says, is the handling of the geopolymer fibre-reinforced concrete: “When it’s cold you have to add a little more water as the all-important consistency depends on temperature and humidity. We also did a lot of tests to optimise the time between layers. Too soon and the previous layer will be too soft; too late and the layers will not bond well. We found eight minutes to be about right – depending on the weather!”

Another challenge is rethinking the design to suit the printer: “The architect’s vision has to be translated in such a way that the printer can understand it. Once you have done that, the machine’s ability is impressive. Our house features curved walls and overhangs which would be hard to build traditionally.”

And of course Aerts is enthusiastic about the environmental benefits: “There is hardly any waste of building material, and no formwork. I like the look of it too. We could have smoothed out the grooved finish, but we wanted people to be able to see and understand how this house was made.”

Kamp C built this house as a demonstration project: “To show what is possible,” says Aerts. “But for the next one, we will be working with developers, investigating how we can bring this technology to the market. Meanwhile, another COBOD printer is creating a three-storey house in Germany.”

Slowly but surely, and layer by layer, it seems printed concrete technology is moving out of the laboratory, and on to site.

Interview by Tony Whitehead

Photos Kamp C & Jasmien Smets