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Preparing for our prefab future

A burgeoning U.S. prefab market has much to learn from Japan

The Muji Hut.
Courtesy of Muji

In the Brooklyn Navy Yard, a massive post-military industrial compound of warehouses converted into creative offices and bespoke manufacturing operations, there is a factory that builds houses. It’s a long, cavernous 100,000-square-foot warehouse with a string of workstations for welding together steel-trussed wall panels, threading them with electrical wiring and plumbing, and finishing them off with drywall and window sashes. Stacks of plywood and steel beams fill large racks next to industrial-sized spools of plastic conduit. It’s a construction site gone linear.


Not long ago this factory was used to fabricate the 930 steel-frame modules that were stacked and interconnected to create 461 Dean, a 32-story, 363-unit residential building that opened in 2016 adjacent to the Barclays Center arena in Brooklyn. It’s considered the world’s tallest building built through modular construction, a form of off-site construction that uses nearly finished sections of rooms and units that are built in a factory and snapped together at the construction site. Originally, 461 Dean was supposed to be one of 15 modular buildings in the 22-acre Pacific Park megaproject, but conflict between the developer, Forest City Ratner, and its construction partner, Skanska, stretched construction time to more than four years, wiping out the savings in cost and time and pushing the developer to fall back on conventional construction for the rest of the project. Immediately after construction on the building was finished, Forest City Ratner sold the factory and all its associated technology.

They didn’t have to look far for a buyer. Roger Krulak was an executive at the company who led the Brooklyn project, and he thought the factory-based building approach could still work. The key was bringing the process under one roof—break down the lines between design, development, and construction, and the delays they saw on 461 Dean would disappear. “Complete inefficiency. That’s what’s wrong with construction,” says Krulak, a 25-year veteran of the industry, as he walks the factory floor.

Krulak became familiar with prefabrication while studying management in Japan in the 1990s, when he toured factories of some of the country’s major prefab homebuilders. Seeing how their systematized factory methods made construction faster, more resource-efficient, and potentially cheaper than conventional building, he knew he wanted to try to replicate Japan’s success back in the U.S. His company, Full Stack Modular, is now operational and focusing on 10- to 45-story buildings, with current projects ranging from a hotel to a mid-rise housing project in Brooklyn to an 11-story building in Manhattan. “We are trying to do it differently and we think we have the model to do it differently,” he says.

Differently for the U.S., at least. This approach to construction is becoming almost mainstream in many parts of the world—from Sweden to Germany to Australia. But the world leader in prefabricated housing is undoubtedly Japan. More than 15 percent of the nearly 1 million new homes and apartments built there last year were made inside factories, either as stackable modular blocks or panelized walls and floors pieced together on empty lots. Millions of buildings now standing in Japan were prefabricated, and several Japanese companies regularly produce more than 10,000 new prefab homes every year. “They’re leap years ahead of where we’re at today,” Krulak says.

In the U.S., only a small number of homes are prefabricated (not counting mobile, or “manufactured,” homes). Annually, only about 2 percent of new single-family homes are constructed through modular means, according to the U.S. Census. Even so, off-site construction has long been seen as the grand solution for the mass production of affordable homes. Everyone from Frank Lloyd Wright to Buckminster Fuller has tried to make a go of industrialized housing in the U.S., particularly after World War II, with startups using mothballed aircraft factories for production. Though a few, like the Lustron Corporation, managed to produce a couple thousand prefab homes here and there, none of these ventures achieved their goal of revolutionizing the production of housing.

Krulak thinks prefab’s time may have finally come in the U.S. With advanced robotics, automation, and digital building information technologies—and increasing concern nationwide about the affordability of urban housing—factory-built housing once again seems poised for wider adoption. And a growing number of companies, from small homebuilders to major hoteliers, are betting that prefab is the future. To understand what that future may look like, you have to go to Japan.


Half of a dining room creeps slowly along a conveyor on a factory floor, with holes where its windows will soon be installed and bundles of electrical wire waiting to be connected with the room’s other half. That chunk is following closely behind on the assembly line, along with a few dozen segments of houses—bathrooms, bedrooms, sections of living rooms—each a box of walls, ceilings, and floors inside a steel frame, as if a typical house had been sawed into precise geometrical forms.

Sekisui House Global Website Channel

“Right now, you’re looking at units for the homes of two or three different customers,” says Toshiya Nomura, a factory boss for Sekisui Heim, the house-building segment of the Sekisui Chemical Company, a Japanese conglomerate that’s one of the largest prefabricated-home manufacturers in the world. We’re standing on a catwalk looking down on the assembly line at Sekisui Heim’s factory in the city of Hasuda, about 25 miles north of Tokyo, where the house parts glide through a series of workstations of robots spot-welding metal beams and rotating wall panels, workers nailing together staircases and slotting in sliding glass doors. In the same light blue uniform worn by the nearly 500 workers clanging away below, Nomura explains through an interpreter that this factory is one of eight the company operates across Japan and that it has the capacity to produce about 150 of these box-like modules per day, the equivalent of about 10 homes. Overall, the company produces about 14,000 houses and apartments per year.

Sekisui Heim, along with about a dozen other major manufacturers, now produces about one of every six new homes built in Japan annually. Prefabricated housing is common in Japan, from multi-unit apartments in Tokyo to modest bungalows in far-out villages to expansive luxury homes in the suburbs. The industry emerged partly by happenstance in the aftermath of the destruction of World War II. In the early 1950s, when Japan was still under Allied occupation and the Korean War was raging, the U.S. military’s demand for steel caused a boom in Japanese industry. After that conflict ended, the companies running those factories began looking for new markets. With the need for housing acute—Japan faced a shortfall of 4.2 million homes in the postwar years—and the population growing, and with the government offering incentives for housing construction, some began building homes. “The growth of the prefabricated housing industry mostly had to do with timing,” says Shuichi Matsumura, a professor of architecture at the University of Tokyo and an expert on prefabricated housing.

What followed was a boom in homebuilding—both among prefab manufacturing companies and the far more plentiful independent carpenters and builders—growing from about 688,000 new housing starts in 1963 to more than 1.9 million a decade later. Since then, Japan has had an unusually high rate of new homebuilding, much of which can be attributed to the fact that Japanese homes depreciate quickly, losing all of their value within 20 to 30 years. When property changes hands, valueless homes are typically torn down and built anew. This scrap-and-build approach has a few interrelated causes: the short lives of low-quality postwar construction; the challenges of renovating to meet building code revisions meant to address Japan's seismic activity; a feedback loop of poor maintenance resulting from the lack of a resale market. The result is that Japan builds approximately the same amount of new housing each year as the U.S., a country with three times the population.

Prefab home builders, like car manufacturers, have taken advantage of this scrap-and-build mentality, continually producing new models of homes with added features and updated safety standards. (A television ad for Sekisui Heim shows an elephant standing safely on top of one of its steel-frame modules. Another shows a frame being dropped from a crane.) According to Matsumura’s research, prefab buildings made up about 7 percent of new homes in the early 1970s. By 2016, they accounted for more than 15 percent.

Sekisui Heim Channel

But conditions are changing. The amount of new housing being built in Japan is slowly declining, as is the country’s population, which is expected to shrink from about 127 million today down to 88 million by 2065. Twenty years from now, more than a third of the population will be 65 or older, and both old and young are already concentrating into metropolitan areas, leaving millions of suburban and rural homes vacant. And with a stagnant economy, the demand for new homes is evaporating.

The country’s prefab manufacturers aren’t waiting for the changing demographics to run them out of business. Instead, they’re doubling down on the design and development of new products to lure in a larger share of a shrinking market, through customizable and flexible home designs, additional luxury appliances and features, and, given the country’s predisposition to natural disasters, advanced safety measures.


“Welcome to the dream factory,” says a man at the front of a theater. He’s in a uniform embroidered with the logo of Sekisui House, Japan’s biggest prefabricated home manufacturer, and the theater is part of a factory and showroom complex in Koga, an industrial city about an hour outside of Tokyo. He starts a film, which uses one of the company’s homes as its set. A multigenerational family is preparing for a potluck. The camera swoops through the house, its kitchen, and out to its patio, where a grandfather is showing his grandson lush crops from the home’s small vegetable garden. As guests arrive, the camera zooms out to show a leafy neighborhood of pristine homes lined around a central green—each a Sekisui House product. Suddenly, the theater’s screen raises like a curtain to reveal a large opening to the outdoors, onto the very cluster of homes featured in the film. The man in the uniform smiles.

The model homes on display in this theater/exhibition space are some of Sekisui House’s top-line products. Replacing shoes with slippers in the foyer, visitors can walk through these furnished show homes, each offering a stylistic theme—from the sleek slate facade and floor-to-ceiling windows of a modernist bachelor pad to the peaked roofline of a suburban McMansion to the indoor-outdoor fluidity of a California Contemporary that could host a summer potluck. Each was fully fabricated in the Sekisui House factory down the road.

In hundreds of locations across the country, often in suburban areas, model homes like these are on display in what are known as housing plazas—outdoor showrooms with full-scale model homes and salespeople eager to offer tours. Big prefab manufacturers like Sekisui House and Daiwa House line their homes up on fake neighborhood blocks alongside model homes from smaller-scale prefab manufacturers like TamaHome and local conventional builders. The homes are bigger than what most people would need, in order for the housing companies to show all the options available.

Safety features and seismic reinforcements are an inevitable part of the walkthrough: Walls and floors are often sliced open and covered with transparent plastic to show sturdy steel beams and cross bracing. High-end appliances and built-in features bedeck every room possible. Typical prefab homes in Japan cost usually in the $300,000s, comparable to conventionally built houses, Matsumura says. These new high-end features are pushing them to higher price points.

One of the bigger housing plazas is located about an hour by train from Tokyo, in a suburb called Tachikawa. About 50 homes are on display here, and a slow trickle of shoppers mills around on a recent Sunday afternoon. Mikiko Okabe, her husband, and her parents have just toured a steel-frame prefab model home built by the company Asahi Kasei. The family is in the market for a duplex they can share. “My parents will live on the ground floor and we will live above,” she says. They decided to look at prefab homes instead of conventional wooden houses because of advertised soundproof floors. “We want to make sure we don’t disturb them,” Okabe says.

Nearby, Shoko Yokota is looking at a conventional wooden home. She’s not interested in prefab homes—too basic, she says—and is instead looking for a home in the style of an English manor one might find in the Cotswolds. She’s never been there, she says, but her husband has. “I love the Old World style, the beautiful tiles.”

Next door, a saleswoman tries to lure Yokota in for another tour by noting that the company’s homes are designed to be furnished by Ikea. “For Scandinavian tastes,” she says.

It’s a significant shift in focus for the prefabricated housing industry, from its roots as a postwar housing solution for the masses to producing primarily luxury homes for the upper-middle class and above. “For the single-family housing industry to survive, we have to focus on the luxury market,” says Noboru Kaihou, a public information officer for Daiwa House.


Bringing down costs isn’t a priority for most of Japan’s prefabricated housing industry, but advances in technology and increasing automation may make homes more affordable anyway. An hour’s train ride from Kyoto is the factory and R&D facility of PanaHome, the prefab homebuilding arm of the electronics company Panasonic, and automation has been integrated into nearly every part of its assembly line. Robots spot-weld steel beams into the panels that are eventually snapped together into homes. A two-level conveyor system pulls the panels along, automatically applying zig-zags of glue and laying down pre-cut interior wall materials. At the end of the row, the conveyor flips the wall panel and sends it back to where other robots and a small team of human workers insert insulation and nail down exterior wall finishes. A five-axis robot arm scans up and down the newly outfitted wall before applying a precise line of sealant in the seams between the exterior panels and around the windows. Elsewhere, another even larger robot arm stacks the completed panels for shipping, layered from top down in the order workers will install them. This factory produces enough panels to build about 16 homes a day.

On the actual construction site, all the automation results in a very quickly built house. PanaHome officials play a time-lapse video showing one of their homes being constructed on a customer’s plot of land. A small crane unloads panels from the back of a truck as workers guide walls and floors down onto a pre-poured concrete foundation. Within an hour and a half, the first floor is complete. A few truckloads later, the whole house is built, floor to roof, in just five hours. (The process typically takes a full work day; “The workers skipped lunch for the video,” a company official notes.)

The overall process for building a PanaHome takes three to four months, involving accommodating a customer’s specific design requirements plus the time to permit the project, demolish any pre-existing building, lay a new foundation, and install finishings inside the completed structure. Though the average cost for a prefab home like this is comparable to conventional construction, the home can be move-in ready in half the time or less. For prefab builders, the speed of construction is a strong selling point.

“On-site construction of prefabricated buildings is very easy and skilled workmen are not necessary,” says Junichi Goda, managing director of the Japan Prefabricated Construction Suppliers and Manufacturers Association. He says that the companies in the association are all looking at how improving the efficiency of the production process can improve the efficiency of construction. He predicts that automation will become even more prevalent in the years to come.

And it may have to. “A major issue in Japan today is the rapid decrease of carpenters,” says Matsumura, the prefab housing expert. In the 1980s, he says, there were about 1 million skilled carpenters in Japan, using traditional joinery and construction techniques to build the roughly three-quarters of homes in the country that are not in some way prefabricated. Now, there are only about 300,000 of these carpenters, and their numbers continue to fall. (In the U.S. there are currently more than 2.5 million people employed in residential construction jobs.) Japanese prefab manufacturers, with their quality control and factory precision, have become a more attractive option in a smaller field of builders.

Architecturally, that may mean an increasingly disjointed urban landscape, according to Azby Brown, director of the Kanazawa Institute of Technology’s Future Design Institute in Tokyo, who’s written extensively about Japanese homebuilding and architecture. “The prefab companies pride themselves on their ability to provide whatever style people want,” he says, “but often they don’t really mesh with their surroundings, or with the traditional urban form.” Prefab buildings are typically standalone single-family homes, unlike traditional Japanese buildings that align their facades to create an almost seamless engagement with the street. “Let’s call it a lack of contextual awareness,” he says. “I guess it’s because the market hasn’t asked for it.”

That could be changing. Some companies and designers are now starting to think differently about the potential of prefabrication, with design as the guiding principle. The minimalist retailer Muji has recently ventured into homebuilding, and has used prefabrication for projects or parts of projects. Known for its plain aesthetic and focus on utilitarianism, Muji began selling homes in 2004, partnering with architects like Kengo Kuma to create prototype homes of Muji-like simplicity. These designs became the basis for industrialized versions, with three models that can be adjusted to customers’ spatial needs and produced in factories. (The company recently expanded its offerings with the Muji Hut, a 130-square-foot one-room cabin marketed as a sleek halfway point between camping and a vacation home.)

The Muji hut.
Courtesy of Muji

So far, the company has sold about 2,000 of its prefabricated houses. “Muji doesn’t intend to do mass housing,” says Koji Kawachi, a registered architect and director of Muji House, the subsidiary company charged with designing and selling Muji’s homes (and huts). He’s leading a tour through a model of the Wood House, outside of Yokohama. The house is a white, two-story rectangular building with floor-to-ceiling windows lining nearly its entire length and wrapped with a ground-floor porch. Inside, it’s filled with natural light from the large wall of windows, and it is surprisingly open for a two-story, two-bedroom home of about 1,100 square feet. “It looks completely different from conventional Japanese houses,” Kawachi says.

The openness is deliberate. The home was designed without full walls separating any of its spaces, save the bathroom. From the second-floor master bedroom, one can look down on the living room and kitchen or across to the other bedroom. It’s partly for energy-efficiency reasons—the lack of walls makes it easier to heat and cool—but mostly an attempt at social engineering. “It makes the bond of the family stronger because each member is not isolated from one another,” Kawachi says. “We’re making a proposal for a new lifestyle for the Japanese people.”

The design is also flexible, he says, noting that as family makeup changes and children grow, walls can easily be added or removed to accommodate new needs—something the typical home is unable to do. Standardized designs and factory-produced components allow the home to evolve with its owners, and potentially to live on to meet the needs of new owners down the line. “Our dream is for this type of house to become a conventional house,” Kawachi says.

But prefab or partially pre-built homes may make their strongest inroads into the current U.S. housing market as a solution to non-conventional housing needs. In Los Angeles, which has the highest unsheltered homeless population in the U.S., plans were recently released for an 84-unit transitional housing complex for the city’s homeless built using shipping containers, a first for the city. The project’s architects, KTGY, cite the ready-made simplicity of the containers as a key to getting the project built in just six months. For other cities grappling with the slow disasters of homelessness and a lack of access to affordable housing, pre-built elements, like containers, are powerful tools.

Japanese architect Shigeru Ban offers one model for using pre-built construction to design for disaster. After the 2011 tsunami that struck the northeastern coast of Japan, Ban—a Pritzker Prize winner famed for unique cardboard-based shelter structures designed for disaster response in places like Haiti and Rwanda—was called on to help design temporary housing for a particularly hard-hit harbor town named Onagawa. Then home to about 10,000 people and sitting inside a small bay, the town’s hillsides had the unfortunate effect of funneling the tsunami into an even taller onslaught of water, nearly 50 feet high, which rushed inland and tore apart roughly 70 percent of the town’s buildings. An estimated 827 people died.

Some of the temporary homes on the edge of Onagawa. These are 3-room prefabricated houses where families now live in.
Patrick Wack/laif/Redux

Ban was tasked with quickly creating 190 temporary housing units, for use by residents as the town recovered and new housing plots could be prepared and distributed by lottery. Lacking suitable flat space for construction, the town’s baseball field was taken over. But the space would have only allowed about 70 of the portable single-story temporary buildings commonly used by the government. Ban proposed a series of rectangular buildings two and three stories tall, built from shipping containers, with interior walls strategically removed to create open spaces and balconies. “My approach solved the problem,” Ban says in his Tokyo office.

Ban says the Japanese government is “not as serious as they should be” about disaster readiness in housing. (More than six years after the tsunami, Ban’s temporary units and their residents are still sitting on that baseball field, under the shadow of its scoreboard.) So he has continued preparing new plans on his own. He’s developed a design for temporary housing based on simple factory-fabricated wooden panels that can be trucked to sites in need. They serve as the structural frame of the building, the basic form of which can be assembled in just two days. The design was put into action in July 2016, after a 7.0 earthquake hit the southern prefecture of Kumamoto. By early September, a temporary home was complete and able to accommodate three families. Key to the speed of construction were the prefabricated structural panels. For Ban, they’re an example of how an industrialized approach to building can not just meet the market’s demands, but also answer a serious need.

“I’m interested in designing a system, not designing houses one by one,” Ban says.


It’s a sign of the future of factory-built housing that Japan’s highly advanced prefabricated housing industry is diversifying into new forms and market niches. It’s also telling that the Japanese companies are expanding outside of their homeland, pivoting away from a shrinking country and economy and toward a growing and urbanizing world. Most of the major manufacturers are either opening or already operating factories in other countries: Sekisui House now has factories in Australia and China; Daiwa House recently began partnering with local builders in Malaysia; Sekisui Heim began building in Thailand in 2013; PanaHome has fledgling enterprises in Taiwan, Vietnam, Singapore, Malaysia, and Indonesia.

Sekisui Heim Channel

Some are even edging into the U.S. market. Sekisui House recently purchased the Salt Lake City-based homebuilder Woodside Homes, and in February Daiwa House expanded a small U.S.-based subsidiary by acquiring a majority stake in the single-family homebuilder Stanley Martin, based in the Washington D.C. metro area. Neither are planning to open Japanese-style prefab factories any time soon. Officials from Daiwa House say they’re interested in understanding the U.S. market before making the significant capital investments a factory would require. And given that modular and prefabricated houses are sometimes treated differently from conventional construction in local zoning codes, the regulatory environment of this bigger market is exponentially more complicated.

Highly automated and efficient prefab factories like the ones in Japan aren’t likely to start popping up in the U.S., at least not at the scale seen in Japan. The postwar dream of one or two companies figuring out the magic formula to take industrialized housing nationwide seems basically impossible. Rather, the revolution in homebuilding will probably be more diffuse, spread out among numerous companies and designers operating at a variety of scales. And the beginnings can already be seen across the country. In the San Francisco Bay Area, Blu Homes is offering “premium prefab living” while Factory OS was recently hired by Google to manufacture 300 modular apartments for a new company campus in Mountain View. East Coast architects like Boston-based Turkel Design and New York-based Resolution: 4 Architecture specialize in custom prefab home design. Companies like North Carolina-based multi-unit modular specialist Prescient and the single-wide, double-wide, and triple-wide builder Champion have factory-made projects on the ground nationwide.

And in mid-October, Alphabet, the parent company of Google, announced that its cities-focused subsidiary Sidewalk Labs would be leading a tech-fueled urban redevelopment of 750 acres of Toronto waterfront that aims to utilize modular building techniques, among many other technological schemes. "The integration of these systems will change the way structures are designed and built," the company claims.

In Brooklyn, Roger Krulak believes the time is right for his startup to crack the 10- to 45-story market. “There’s still a little hesitancy, but that hesitancy is diminishing,” he says. The 32-story 461 Dean project in Brooklyn is high-profile proof that it can be done, he says. And on the production side, the availability of advanced building technology helps, as do increasingly applicable best practices from the Japanese prefab industry—practices Krulak is gradually integrating into his own factory. In the end, it’s all about making it easier to get stuff built. If prefabrication offers an advantage over conventional construction—whether by lowering cost, shortening construction time, or reducing reliance on a shrinking pool of skilled labor—to Krulak, the choice seems clear.

“There is a huge housing disaster around the world, and the current process just doesn’t work. We need a different solution,” Krulak says. “To me, that is the driver.”

Travel for this article was supported by the Abe Fellowship for Journalists, a reporting grant from the Social Science Research Council, and the Japan Foundation Center for Global Partnership.

Editor: Sara Polsky

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