How to print a house

At home late one night, an energy drink in one hand, the 3Doodler pen in the other, Platt Boyd had his breakthrough. Like hot glue from a gun, the molten plastic secreted by the 3Doodler hardens as it cools, which allows the user to draw 3D shapes. Boyd drew a small scaffold, an object that crudely represented the three-dimensional diagrams of compounds a high school student might study in chemistry class. When it solidified, he set one book on top of it. Then another, and another. Eventually the tiny 3D object he had created minutes before was holding up 18 pounds of books. It weighed half an ounce.

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At the time, Boyd was a partner at a regional architecture firm based in Birmingham, Alabama, doing what everyday architects do: dreaming up boundary-stretching designs without a shot at ever seeing them built. “What I as an architect wanted to have was the freedom to design things like all these starchitects,” he says. “All of these normal architects are frustrated because the building technology isn’t there to realize it unless you have these huge budgets.” Using normal building materials, the sort of design freedom Boyd wanted could cost between $800 and $1,000 a square foot, by his own estimate, or even more.

But that night in 2014, doodling with a children’s toy, Boyd saw a way to make the designs in his head a reality.

Boyd envisioned a 3Doodler pen on a massive scale. Constructing a free-form house with such a machine would drop costs to around $200 a square foot, he figured. In April 2014, Boyd left the firm he had been with for 15 years and founded Branch Technology, one of the latest in a string of companies worldwide racing to upend the construction industry using 3D printing.

The concept of additive manufacturing—the more technical term for 3D printing—dates back to the 1980s but has become much more popular in the last decade, thanks to companies, such as Brooklyn-based MakerBot, that shrunk the necessary hardware so that it could fit on a desktop. Using powdered metals or plastic, a 3D printer employs heat and force to fuse together materials, layer by layer, until a fully 3D-printed object is created. In recent years, companies in a variety of industries have turned to 3D printing to streamline manufacturing processes and produce parts, like fuel nozzles for airplane engines and dental implants.

Now 3D printing is making its way into single-family home construction. Eric Schmidt, executive chairman of Google’s parent company, Alphabet, named 3D-printed construction one of the next moon shots at last year’s Milken Global Conference. Instead of powdered metals and plastic, mixtures of cement, sand, and plastic-polymers are the building materials. Instead of stationary, box-like machines, large robotic arms on a swivel produce fully functional houses, with electricity, plumbing, roofs, and windows.

In December, Apis Cor, a startup with offices in San Francisco and Russia, printed what it claims is the world’s first “on-site” house outside Moscow. In 24 hours, the company used a cement printer to construct a 400-square-foot house. Elsewhere abroad, other entrepreneurs, architects, and firms are constructing houses and buildings using 3D printing. Dutch firm Dus Architects spearheaded work three years ago on a 3D-printed, full-size canal house to demonstrate the capabilities of 3D printing for construction; it followed that up last summer by printing an 86-square-foot cabin in Amsterdam out of recyclable bioplastic. In the United Arab Emirates, a $140,000, 2,700-square-foot open office made of concrete and designed by international architectural firm Gensler was unveiled last May. In China, the company WinSun has made 3D printing a step in a prefabrication process to print, using a mixture of cement, sand, and some other substances, walls and other pieces off-site that are then assembled into buildings.

And, of course, there’s Enrico Dini, an Italian civil engineer and the inventor of the D-Shape, a massive 3D printer capable of printing entire houses. Many of today’s efforts to make 3D-printed construction a reality owe their efforts to the work Dini did during the late 2000s.

Pioneers of 3D-printed construction rattle off what they see as numerous advantages: decreased costs and the consequent ability to follow through on their inventive architectural plans, as well as simpler and sturdier houses built more quickly. The price is lower for homebuyers, too. The house Apis Cor built last December cost just over $10,000. By comparison, a three-bedroom, 1,050-square-foot house built by Habitat for Humanity costs roughly $50,000.

Even if 3D-printed home construction is the wave of the future, barriers remain. Testing the materials and the equipment to print them is an expensive process. Materials must, to comply with existing regulations, be fire retardant and offer UV protection. Not to mention that the construction industry is slow to change, especially in the U.S., where framed wooden houses have been the norm for decades.

“All of these convergences take a long time sometimes,” says Cindy Frewen, Kansas City-based architect and chair of the Association of Professional Futurists. “Right now these 3D-printed homes are just demonstrations more than a trend. But I think a new era is coming.”

This year could be a tipping point for the start of widespread 3D-printed home construction in the U.S. People at the vanguard of 3D-printed construction plan to roll out construction machines and build 3D-printed homes this year. And by the end of 2017, Boyd hopes to finish an 800-square-foot home in Chattanooga, Tennessee, where his new company has its headquarters. Two years ago, Branch sponsored a contest for architects, with a $10,000 prize, to design a 3D-printed house using the company’s technology. The winning house, dubbed Curve Appeal, was designed by the Chicago-based Urban Architecture Studio of WATG, an internationally acclaimed architecture firm founded in 1945.

In 20 or even 10 years, the house that now takes weeks to build might be done in a matter of days.

“Everybody’s dream is you hit the button and boom, your house pops out, and it’s ready to live in,” says Chris Hurst, one of the designers of Curve Appeal. “That’s the market, and it’s something we can do relatively soon.”

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Engineering professor Behrokh Khoshnevis was an early pioneer of house printing, sometimes referred to as its grandfather.

Khoshnevis, director of the Center for Rapid Automated Fabrication Technologies at the University of Southern California, began experimenting with 3D-printed construction as early as 1996. Over time, he developed what he calls Contour Crafting, a building method that makes use of a large, computer-guided robotic gantry outfitted with nozzles. The machine follows the outline of a house; from foundation up, it deposits a concrete mixture layer after layer until a roof is ready to be placed on top. Walls are hollow to allow for the conduits needed to install electricity, plumbing, heating, and air conditioning. The goal, he says, is full automation of home construction.

“It’s going to be cheaper, faster, more consistent, and less hazardous to humans,” says Khoshnevis, citing statistics from the International Labor Organization that place the number of deaths at construction sites worldwide at 60,000 each year.

He recently founded Contour Crafting Corporation, which plans to start selling an entry-level version of his Contour Crafting machine to contractors in late 2017. The plan is for his company to operate the machines for contractors, and then eventually offer training on the machines so contractors can use them on their own.

Branch Technology, on the other hand, uses a process more akin to prefabrication. The company currently has three hulking robotic arms in its downtown Chattanooga studio. Affixed to each arm is an extruder head that pushes out 3D-printed material. Those robotic arms assemble systems of matrices: cross-hatched, three-dimensional patterns of hardened material. One such arm is a 12-and-a-half-foot machine that travels along a rail on the ground and is able to print a matrix that’s 25 feet wide and 58 feet long. Stand up enough of these matrices and you have the frame of a house.

The concept is derived directly from Boyd’s time messing with a 3Doodler. After he built that first tiny matrix, he took a trip to Home Depot for supplies—a pipe, an auger bit, some portable heaters—to rig up a prototype of Branch’s system. Using it, Boyd printed a 2-ounce piece that held his weight, 160 pounds. After testing materials and build density, Boyd eventually printed a 2-pound matrix. It was made from carbon-fiber-reinforced plastic and, once it was reinforced with spray foam insulation, held 6,000 pounds.

“We’ve developed the hardware and the software to free-form 3D print so that it solidifies in open air,” says Boyd. “We prefabricate those frames, and then ship them, and then fit them together like Legos on-site.”

Today the robotic arms are supplied by companies that specialize in automation, but the concept is the same. Curve Appeal, in part, will be constructed this way. The exterior and interior walls as well as the roof, and maybe some of the furniture, will be 3D printed by Branch. The rest of the house is something that could be plucked from your own home.

While Khoshnevis is going to contractors with a machine and Boyd begins house construction this summer, Minneapolis-based Andrey Rudenko plans to print several houses this year on his own as a way to prove the technology works. He says by the end of 2017, there will be three houses made from 3D-printed construction: one in California, one in Florida, and one in his home state of Minnesota.

“I can print any shape, and it takes two or three days to print a house. At the same time we are installing electricity, wires, plumbing—everything,” he says, as opposed to the usual approach of running all the wiring and plumbing after the house is framed. “They are going to be gorgeous houses with contemporary design.”

Rudenko has been in the construction business since he was 16 years old. An engineer and architect originally from Russia, he was a contractor near Moscow, building houses, nightclubs, and restaurants, before he immigrated to the U.S. Rudenko’s name first hit the online 3D printing trade publications in 2015 when he built a 3D-printed castle in his backyard, using a machine he developed that operates similarly to the robotic gantry used in Contour Crafting. The castle, built from a mixture of fine concrete, plus some other additives, was constructed layer by layer, just like a 3D-printed Yoda head that comes out of a desktop 3D printer.

Rudenko knew the same technology could be applied to building houses, and his experience in the construction industry is what spurred him to develop newer versions of his original machine.

“The reason I started using 3D printers is because I clearly saw the construction technology was really outdated,” he says. “We are going to Mars, everybody has smart phones, but in construction, it’s the same as it was 50 years ago.”

Courtesy of WATG

There are reasons for the slow place, some economic, some rooted in safety. Both will prove to be challenges as developers of 3D-printing construction technology move forward.

The home industry usually thinks in terms of 30 years or more, says Peter Ebner, an architecture and urban design professor at the University of California, Los Angeles. A contractor who has been building wooden houses for years isn’t going to suddenly adopt a new means of building residences, even if people like Rudenko and Khoshnevis say it could cut costs by as much as 30 percent.

Testing the durability of 3D-printing materials is also a tedious and expensive process. Right now, Branch is trying a variety of building materials—plastic polymers reinforced with carbon fiber and glass, as well as some biopolymers—paid for by a $750,000 grant from the National Science Foundation.

“In Germany, for example, you have to get a certificate to show that building material will last 30 years or longer. How do you prove it with a new structure?” says Ebner, who worked as an engineer in Austria and Germany before heading to UCLA in 2009. He has his own experience comparing conventional and 3D-printed construction. In 2014, he and a group of students created a 3D-printed, 50-square-foot micro-house at UCLA’s 3M futureLAB, named after the Minnesota company better known for Post-It notes and Scotch tape.

Additionally, the construction business overall is big, expensive, and custom, three factors that make an industry loath to change. “There’s an innovation gap going on, and a need for some real, new ideas. But construction in general is very behind the times,” Frewen says. It also knows what works, and what’s permitted—especially when it comes to residential buildings, and especially in the U.S.—and doesn’t need to run a gauntlet of local and state code officials to get approval for a new construction method.

“As long as it’s conventional construction, if you’re using wood or steel like normal, I don’t need any plans,” says John Haustein, a plans review specialist with the city government of Chattanooga, where Boyd’s Curve Appeal home is to be built. “If you’re doing something innovative, I need to see building plans. Then I’m going to need some engineering to show that it will hold up to 90-mile-an-hour winds and a 10-pound snow load on the roof.”

And those standards, for obvious reasons, are not uniform across the U.S.

“Within the U.S., there’s no one set of codes or regulations that apply everywhere. There are differences regionally,” says WATG’s Miguel Alvarez. “And for a lot of difficult assemblies, they’re all known quantities and there’s a whole knowledge base that’s readily applied to those constructions. That doesn’t exist for 3D printing.”

Local and state building codes in the U.S. work from standards established in the International Building Code and the International Residential Code, both of which fall under the purview of the International Code Council, which provides technical support to government agencies that oversee building codes.

To prepare for 3D-printed construction, the ICC partnered with America Makes, the National Additive Manufacturing Innovation Institute, and the American National Standards Institute to put together a standardization roadmap for 3D printing across major industries, including construction, that just published in February. When these standards are finalized in the next couple years, the ICC plans to use them to create a regulatory framework around 3D-printed construction, according to CEO Dominic Sims.

“The IBC is at the core of our plans to modernize the International Codes in preparation for additive manufacturing,” Sims told Curbed by email.

Assuming the regulatory structure in the U.S. is worked out sooner than later, there’s one last hurdle Khoshnevis, Rudenko, and other aspiring printers of homes will have to jump: Who wants to live in a tiny, 3D-printed house made of concrete? For now, because of the size of the machines, there are limitations to what can be built, as well as questions around the visual aesthetic that a 3D-printed house can achieve.

“Right now, this is not very elegant, and there’s a lot to be said about quality… It’s a long way before you could say it’s the same as customized housing,” Frewen says.

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The purveyors of 3D-printed construction dispute the notion that a 3D-printed house, even a concrete one, is ugly or unappealing. Branch’s method, for instance, was recently used by the New York-based firm SHoP Architects to create a 200-by-100-foot outdoor pavilion for Art Basel. SHoP designed the lattice-like pavilion, and Branch created it out of 3D-printed biodegradable bamboo. The pavilion was the winner of the Design Miami fair’s Visionary Award.

And the companies developing 3D-printing construction technology are doing so with an eye toward building two-, three-, even four-story homes, or larger single-story houses. One company, Sunconomy, plans to use Apis Cor’s printer to build houses in Montgomery, Texas, and is advertising floorplans with two bedrooms and two bathrooms.

Still, sometimes it’s easier to build outside the U.S. Rudenko plans to build just a few 3D-printed houses here, but is in the beginnings of a master plan to print 10,000 houses in Russia.

“The whole industry here works toward building framed houses, wood houses. It just takes too much time and energy to discuss how we can switch to concrete,” he says. “It’s actually much easier to print in Asia and Europe, because they’re used to using concrete for traditional houses.”

While Branch Technology doesn’t print in concrete, the hope is that Curve Appeal will start winning over converts from the construction industry. As designed, the house is a winding, curvy residence replete with archways, something even a concrete printer is capable of building, with few of the sharp angles common in conventional home construction.

“If you Google ‘parametric architecture,’ you’ll see all these amazing designs in the computer. Hardly any of them are built because it costs so much,” says Boyd. “Well, now, through 3D printing, those things can be realized. It enables really a more beautiful architecture.”

And that’s the point, Boyd says—to demonstrate that, with 3D-printing technology, even everyday architects or homebuyers on a budget can afford not only a house, but also one that’s unlike any other on the block.

Editor: Sara Polsky