Using 3D printers to build houses

The take-away

  • Digital construction processes save time and money. Walls, for example, take three days instead of three weeks to build.
  • In Europe, 57% of all construction activity is redevelopment. 3D printing is particularly well adapted.

The robot looks like a pastry chef spraying cream on elongated pieces of pie. A white liquid shoots from the robot’s arm, swelling and solidifying until a wall-like structure begins to take shape. In Nantes in western France, the construction site of the future is a reality: robots are using 3D printing to build houses from digital blueprints. The white liquid is polyurethane, a plastic used as insulating material. The plastic forms two parallel walls between which concrete is poured, using the same technique, to form the basic structure. On the inside, the walls are then covered manually with plasterboard; on the outside, with plaster. Beginning next year, the 95-m2 house will house a family. It is a world première: although some buildings have already been built with 3D printing in China and Russia, these are not inhabited.

“The house meets all building regulations,” says Benoit Furet, project manager and researcher at the University of Nantes. “Ten more houses are already planned.” The advantages of this digital construction process: since neither concrete forms nor scaffolding are necessary, time and money are saved. The walls, for example, take three days instead of three weeks to build. “3D printing also makes building with curves easy,” says Furet. “This is important because buildings lose the most heat in corners. In the conventional building process, curves are often unprofitable because the formwork or the building material has to be manufactured individually or cut to size. ”With the new technology, the house in Nantes has no right angles. In combination with the polyurethane, a 40% improvement in thermal insulation can be achieved.

Furet and his team are not alone. Several European projects show how robotics and 3D printing can be used in construction. As early as 2011, four flying robots demonstrated in a museum in Orléans how they could team up to build a six-metre-high tower consisting of hundreds of polystyrene building blocks. At the Dresden University of Technology, a research team is working on producing concrete in 3D printing, as in Nantes. The Technical University of Munich (TUM) is focusing on the purely mechanical properties of robots. In its “Hephaestus” project, the research team is developing a cable robot that can be used on building façades for both construction and maintenance. Controlled by a cable system mounted on the roof, the robot is especially useful for very tall buildings.


Tour Bel-Air in Lausanne

New 3D digital models were used to install new insulation and ventilation systems in the Tour Bel-Air, a skyscraper in Lausanne (Western Switzerland).

More complex than cars

According to British building company Balfour Beatty, construction in 2050 will have no workers, only robotic teams and drones supervising the site. All will be planned and controlled by algorithms that create 3D and 4D models. For the time being, however, construction remains highly dependent on analogue processes and, above all, manpower. This is no surprise for Thomas Linner of TUM’s Institute of Building Realisation and Building Informatics. “On one hand, there are often very large and heavy parts in buildings, where today’s robots quickly reach their limits,” he says.

“On the other hand, local requirements must always be taken into account during construction, such as climate or specific material uses. And there are more variable components than in the automotive industry.” Nevertheless, he notes that automated construction has been steadily gaining ground. “This is due mainly to the new legal requirements for energy efficiency in Europe. Robots and 3Dprinting can save a lot of costs and material.”

According to Benjamin Dillenburger, professor of digital construction technologies at the Institute for Technology in Architecture at ETH Zurich, 3D printing raises basic questions. “Even today, there are automated processes for the prefabrication of certain components for standard buildings,” he says. “3D printing would not necessarily be profitable here.” In his view, this technology makes more sense for exceptional, non-standard models, as well as for specific construction steps. What happens when various digital functions are specifically used can be seen in the “DFAB House” project, which Dillenburger is currently working on together with several other professors from ETH Zurich at a research building (“NEST” of the Empa and Eawag, two Swiss research institutes) in Germany.

The load-bearing wall on the ground floor of the three-storey building is being built by a mobile robot, approximately two metres in size, using the so-called “mesh mould” method that researchers have developed from robotics, materials science and structural engineering. To do this, the robot first builds a steel wire mesh according to 3D models, into which concrete is then poured manually. Due to the grill’s fine mesh, the concrete cannot flow out; the wire framework thus serves as both formwork and reinforcement. As in Nantes, the supporting wall is not right-angled, but doubly curved. The formwork is made with a large-format 3D sand printer and then filled by hand with shotcrete. Printed formwork also makes complex shapes in concrete possible. The ceiling is geometrically highly differentiated, In order to distribute material only where it is structurally necessary.

As a result, more than half the concrete can be saved. Another innovative construction step is the wooden construction of the two upper floors. These are prefabricated and assembled as part of the “Spatial Timber Assemblies” project in what is currently the world’s largest robotics laboratory in the architectural field at ETH Zurich. The 200-m2 house, to be completed in the summer of 2018, will serve as living and working space for guest researchers.

Assistants on the building site

Unlike emerging countries, Europe focuses on redevelopment, which accounts for 57% of all construction activity. Dillenburger particularly values the potential of 3D printing technologies here, since in most cases tailor-made solutions are required for recompacting or extension constructions. However, a key to efficient building renovation is powerful 3D digital models. Bernard Cherix of the École Polytechnique Fédérale de Lausanne develops such models with the aim of aligning them optimally to the needs of building renovation. He was involved in the renovation of Switzerland’s first skyscraper, the Tour Bel-Air in Lausanne. “To install new insulation and ventilation systems, it was important to simulate them in digital models”, explains Cherix.

In addition, individual elements of the building were raised. Here too, it was necessary to simulate these steps to avoid distorting the building’s external appearance. These models allow for more efficient construction by eliminating errors and saving material. “3D printing and robotics can be helpful if used selectively,” says Cherix. In contrast, he sees great potential in the application of AI technology in digital3D models.

Furet also sees hurdles for wider application of 3D printing and robots in building construction. “For now, we can build only single-storey houses with our robot. They would have to be lighter to be able to work on several floors.” He also sees limits in the construction of horizontal components. Is the goal of a fully automated construction site too ambitious? Linner is uncertain. “Construction sites will eventually become like factories,” he acknowledges. “But I don’t believe in complete automation. Digital technologies will play a supporting role, but people will continue to be needed in the preparatory and subsequent work.”