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These cute backyard houses can be entirely 3D-printed

Even the roof.

Inside a warehouse in Oakland, California, a 20-foot-high printer recently 3D-printed the shell of a tiny house—not only the walls and floor, but the ceiling and roof, and overhangs. The home took a total of 24 hours to print; similar homes will soon be trucked to backyards in nearby cities.

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Mighty Buildings, the startup that developed the technology to print the home, says that by automating more of the construction process, it can make homes more affordable. Compared to an average house in California, the new homes cost as much as 45% less. They’re also less expensive to build than other factory-built housing.

[Photo: Mighty Buildings]
The company isn’t the first to use 3D printers to build homes; an entire neighborhood of 3D-printed homes is being completed this year in Mexico. But because the new process can print more elements of a house—the homes in Mexico use 3D printing only for the walls and floor—it helps reduce the cost further. “As soon as you are able to produce not only the walls but also floor and ceiling, that saves a huge amount of hours, and specifically labor hours, which are very expensive,” says Slava Solonitsyn, CEO and cofounder of Mighty Buildings. The company’s process automates up to 80% of the total construction process. The rest—including the windows, plumbing, and electrical happen on-site. A “bathroom pod” is made by another supplier manually, and is then installed separately.

[Image: Mighty Buildings]

That’s particularly helpful in California, where construction is especially expensive, and the construction industry doesn’t have enough workers. “We’re not trying to replace labor,” says Sam Ruben, chief sustainability officer at Mighty Buildings. “What we’re trying to do is address the fact that we have a labor shortage, particularly skilled labor in the construction sector . . . What it’s really intended to do is make their job easier and faster and increase that throughput so that at the end of the day, hopefully, they’re actually going to have more work, not less. It’s just going to be less work per unit, but more work overall for a greater number units in order to get all those houses out in the market and close that affordability gap.” A McKinsey Institute report in 2016 estimated that the state needed to build 3.5 million houses by 2025—an unprecedented rate of construction—to meet demand and lower the cost of housing.

While it would be possible to print the homes on-site, the company says that it’s more efficient to work inside a factory, where construction can happen year-round in a controlled environment. The process uses far less space than other prefab construction, which typically uses multiple stations in an assembly line. The company aims to build small factories in the urban markets that it serves, ultimately partnering with developers who will place large orders for homes, rather than one-off sales to consumers. The buildings can be permitted at the state level (they are legal currently in California, for instance) and mass-produced, although the technology makes it possible to also easily customize each design with software.

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[Photo: Mighty Buildings]
The startup, which launched from stealth today and graduated from Y Combinator’s tech accelerator in 2018, developed a synthetic, lightweight stone material similar to Corian, a material sometimes used in countertops. As the material is printed and exposed to light, it creates a reaction that immediately hardens it. “It literally freezes in air,” says Solonitsyn. It can support its own weight, making it possible to print horizontally in the air. (A demonstration video with a prototype home shows workers adding support for the roof, but the company explains that it added this for redundant safety, and as the permitting official become more comfortable with the new method, future homes may be printed without this extra step.)

Building this way also has environmental advantages. A typical wall might use a dozen materials; Mighty Buildings uses a single material, preventing waste (Channels to install plumbing and electrical are printed as part of the process). The form of the house also makes it more energy-efficient. “From a sustainability standpoint, by being able to print the roof and the floors as well as the walls, it allows us to create monolithic shells that increase the airtightness, reduce the thermal leakage, and increase the overall energy efficiency of the structure, making it really easy to meet California zero net energy standards,” Ruben says. “We can even go past that into Passive House and other standards that are on the cutting edge of what energy efficiency can do.”

The company is making homes in a variety of sizes, ranging from a 350-square-foot studio (starting at $115,000, with permitting fees, foundation work, delivery, and other steps bringing the total as high as $223,000) to a three-bedroom, two-bathroom house. It’s focused at first on the market for accessory dwelling units in California backyards, where it’s quicker to get permits and begin construction than on empty lots. The first homes they’re selling aren’t fully 3D printed—they have a traditional roof—but by next year the company plans to shift to fully 3-D printing each unit.

But the process can also be used in larger single-family homes, and the company is now working on a material that could also be used in apartment buildings. “We’re actively developing a fiber-reinforced version of our material that already is showing preliminary structural properties similar to steel,” says Ruben. “We’re really excited for that to unlock the ability to move into multistory and multifamily, because we recognize to really address the housing affordability crisis in urban areas, it’s going to require density and that ability to get vertical.”


Correction: We’ve updated this article to clarify that the units currently under construction by Mighty Buildings are not entirely 3D-printed, but the next iteration will be.

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About the author

Adele Peters is a staff writer at Fast Company who focuses on solutions to some of the world's largest problems, from climate change to homelessness. Previously, she worked with GOOD, BioLite, and the Sustainable Products and Solutions program at UC Berkeley, and contributed to the second edition of the bestselling book "Worldchanging: A User's Guide for the 21st Century."

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