Nobody Has 3D Printed a House in 24 Hours

There is more to a house than just walls. Danish company COBOD tells the truth about it.

We have long been skeptical about 3D printing of buildings, calling it a solution looking for a problem. Most of the printers we have seen and shown squirt concrete out of a nozzle on a robotic arm and slowly build up layers of wall. But in normal construction, walls are the quickest part of a building and only a fraction of the cost of the finished, useful structure. When I last wrote about this, readers disagreed with me, the first commenter saying, "What a stupidly conservative view... the article is absolute garbage."

So it was really surprising to see a report from a company making 3D printers saying many of the same things. COBOD, a Danish company making gantry-style printers, has issued a document called THE TRUTH: facts about the true state of the art of 3D construction printing.

© COBOD

In it, they diss the competition like Winsun, Apis Cor and ICON for claiming that they built houses in 24 hours, as ICON claimed and Kim wrote about, when none of them actually did. But more importantly, they note that nobody has 3D printed an entire building. Only the walls are 3D printed (although Winsun's tilt-up system does do ceilings).

© COBOD

• So far, all projects related to buildings done with 3D printing on site have limited the use of the 3D printer to only printing the walls.
• Roofs, slabs and floors, thus, still need to be made the traditional way; similar for plastering, painting, cabling and plumbing.
• Hence, in essence it is wrong to state that a complete building was 3D printed. It is more correct to refer to, that the walls of the building was 3D printed in a certain amount of time.
• So far, in general, 3D printing only takes care of 20-25%, which the walls make up of an entire building, while conventional methods are still responsible for the remaining 75-80%.

© COBOD gantry printer/ Photo COBOD

COBOD did build a house in 28.5 hours of printing over 3 days, with their gantry crane design. It looks similar to the original printer proposed by Professor Behrokh Khoshnevis 20 years ago. Many companies are now working with robotic arms, but COBOD says Gantry designs are better:

We believe there is fundamentally a choice to be made between a robot arm printer and a gantry type printer. Generally speaking the robot printers have the advantage of being more mobile/movable than gantry printers and of being able to print certain prints due to the 6 axis movement that gantry printers would have difficulties with. Gantry printers on the other hand typically have cost and stability advantages, offers the ability to make larger prints and even print entire buildings in one go (as opposed to the more limited prints of robot printers and the robot printers need for printing single elements).

© COBOD

I am not sure either is an answer to the problem of building affordable housing in a hurry. 3D printing is still best at doing one-offs and prototypes, so it might slowly print a rocket nozzle but be faster than a machinist. A cement printer can print the walls of a small house in a little over a day. On the other hand, a computerized robotic wall-building machine like you see in Sweden can crank out all the walls of a house, with insulation, electrical wiring and windows in an hour, which can be shipped as easily as a bag of cement to a site and assembled in another hour.

© COBOD

I do believe that original commenter is wrong. I am not stupidly conservative. I am an architect and a professor teaching sustainable design who has worked in the prefab industry. I believe that 3D printing of buildings has a place, probably on the moon. But here on Earth, we need lots of housing fast, we need more than just walls, we need natural materials instead of concrete, and the real innovation is taking place in factories, not in the field.

I applaud COBOD's honesty and realism, but I still don't see what the problem is that they are solving.