A white cowboy hat in hand and hair clinging to the sweat on his forehead, Jason Ballard paces around an 11 1/2-foot-­tall 3-D printer named Vulcan II that stands on a slab of concrete atop a small hill. It's a late-spring day on the outskirts of Austin, the temperature pushing 90 and the humidity not far behind, and the machine is not working--and nobody can figure out why.

Ballard squints in the midday sun. "People see these unbelievable stories about this technology, like there are no problems," he says.

Despite its stubbornness today, the Vulcan II is a very big idea. The giant printer--which Ballard's startup, Icon, devised as a radical new way to construct homes--squirts out continuous beads of concrete that stack up to create walls, in whichever configuration a builder may want. It can spit out the walls of an entire small house in just 24 hours. Construction is a trillion-dollar industry in the U.S.; 3-D-printed buildings could strip out as much as half the cost of building a home, Icon predicts. Consider what this means for the more than one billion people around the world who lack adequate shelter--and also consider that, once 3-D-printed buildings are commonplace, hundreds of millions of tons of construction waste could be eliminated every year.

But first, the Vulcan II needs to work. This week, Ballard and the Icon team trucked their freshly built construction robot out of the lab and into the field for its inaugural real-world printing, of a community center in a neighborhood called Community First! Village--a clutch of tiny homes occupied by formerly homeless people. They printed the first three layers of the walls on Monday, and then prepped for what they hoped would be a full day of printing on Tuesday, during which they theoretically could have completed the structure, save for the roof and finishes. But that morning, the concrete that emerged from the printer was too dry. The team cleared hoses, made adjustments, and tried again--and then had concrete soup. So it went for 15 hours: Try to print, make tweaks, try, tweak, try again. Now, on Wednesday, the investigation continues.

Like lab-grown meat or self-driving cars, 3-D-printed housing seems like a science-fiction fantasy come to life--which is why Icon became an overnight sensation in March 2018, when it unveiled a tiny home it had printed with Vulcan II's predecessor (called, naturally, Vulcan I) at Austin's SXSW conference. The company quickly raised $9 million in seed funding from top venture capitalists and com­panies such as D.R. Horton, the nation's largest homebuilder, and was covered by every media outlet from House Beautiful to Fox News.

"What the Icon team has accomplished in such a short period of time is not only a transformational breakthrough in homebuilding--it is an inspiration for the entire world to think outside the box about how humanity will confront the global housing crisis," declared Jason Portnoy, an early PayPal executive and the founder of the Silicon Valley venture capital firm Oakhouse Partners, which is Icon's lead investor.

Now Ballard has to live up to the hype. And reality can be messy. "These are the moments you decide what kind of company you're going to be," he says, as a newly hired materials science PhD and other staffers peer at yet another concrete sample. "It's easy to work for a company where everything works perfectly right away. But rockets blow up the first few times."

He would know.

Wiry, boyish, and intensely spiritual, Ballard speaks with a gentle Texas twang that gives even his wonkiest academic references to E.O. Wilson or Carl Sagan the sound of country wisdom. When he discusses his most audacious, against-the-odds goals, he sounds more like a preacher than a Silicon Valley striver. Among his staff, it inspires devotion. "I have trouble persuading people to go home at night," says Dmitri Julius, Icon's director of operations, who also worked for Ballard at his previous company, a chain of green home- improvement stores. "He's one of the smartest, most magnetic and jovial people I've ever met."

Ballard grew up "behind the pine curtain" in deep East Texas--Orange, to be precise, not far from the Louisiana line--where the landscape turns from open plains to piney woods and bayous, and where the level of poverty not long ago meant that people sometimes hunted possums or raccoons for dinner. While his parents are solidly middle class, when he earned his degree in biology at Texas A&M, he became the first in his family to graduate from college.

After college, in the late aughts, Ballard was working on construction crews for green builders in Colorado and noticed that there was no single place where his employers could get sustainable materials. Sourcing them in bulk was difficult and expensive. He started mulling what a sustainable home-improvement chain might look like, and called a college friend, Evan Loomis, who was then working on the East Coast as an investment-banking analyst covering the homebuilding industry. The two started drafting a business plan. Ballard's wife, Jenny--they'd met at a barn dance when both were counselors at a Christian summer camp in Colorado--came up with the name: TreeHouse.

Ballard was also working toward a different dream: to enter seminary and become an Episcopal priest. One day in 2010, Jason and Jenny went to meet with the bishop of the Texas diocese--largely a formality in which Jason would get the man's blessing to pursue the priesthood. But the conversation turned to Ballard's other passions.

"Jason," the bishop finally said, "you seem to be motivated by tackling big problems. That's what makes you want to be a priest. But I want you to be open to the idea that you're going to exercise your priestly calling through TreeHouse. I want you to try with all your heart to finish what you started. The church will always be here." He said a prayer over the couple, and a business was born.

Ballard and Loomis teamed up to raise a $6.8 million funding round, led by Container Store co-founder and fellow Texan Garrett Boone, who would become the company's chairman. They took the advice of investors and recruited two executives from Home Depot, since they had no real experience in the field. One of those veterans became CEO. Loomis signed on as president and Ballard as vice president, focusing on product selection and services.

The first TreeHouse opened in an Austin strip mall in late 2011, and was a notable misfire. Rather than being something radically new and innovative, it was a pricier but typical big-box store, with high shelves stacked floor to ceiling with hardware--just like Home Depot. It failed to meet sales goals, and within two years, the board pushed out the entire leadership team except for Ballard, and asked him to be CEO. He had just turned 30. It was time to make good on his promise to the bishop.

Then Jenny was told she had breast cancer--while she and Jason had two babies at home, one of whom, they'd just learned, had epilepsy. They prayed hard and decided he should take the job. The doctors had caught Jenny's tumor early, which simplified treatment. "We said, 'It's a year of surgeries. Let's just knock this out and move on,' " she says. "It's a bump in the road, not a hole."

"It became clear to me," Ballard remembers, "that if TreeHouse ran the normal retail playbook, we were going to die, because retail is dying." He immediately rebuilt TreeHouse as a kind of collaborative project-planning space and showroom, where customers could sit down with, say, a solar-panel expert to map out an installation and work through the finances. Sales grew. Ballard scored a deal to be the first retailer anywhere to carry the Tesla Powerwall residential-energy-storage unit, and outsold much larger competitors for hot home brands such as Nest and Big Ass Fans. "If TreeHouse doesn't end up working," Boone took to saying, "there is no truth in the universe."

By early 2017, the company was preparing a new Dallas store, and planning several more. Ballard had begun assembling a tech team, and they had created a virtual-reality tool for doing walk-throughs of the new stores to figure out optimal floor plans and to serve as a neat tool for TreeHouse's project consultants (salespeople) to use with customers to help plan home improvements.

But Jenny's cancer came back, and this time the prognosis was dire. She would have to undergo a wrenching chemo­therapy regimen, and it wasn't clear if she'd survive.

Ballard had been an avid cross-country runner in college, and, as a coping mechanism, he returned to his old sport. In the middle of the night, after working all day at TreeHouse, caring for his sick wife and two children, and getting them all to bed, he would quietly slip out the front door and start running, with no destination in mind. Some nights he ran 30 miles, while his family and employees slept. "I can sleep when I'm dead," he told Jenny.

He supported Jenny during each of her weekly chemo sessions. She supported him when he signed up to run the Leadville Trail 100, a 100-mile ultramarathon in the mountains of Colorado. "If I'm going to live, then we should keep living," she told him. "And if I'm going to die, then we should keep living." She was still undergoing treatment in August 2017, when he ran the race--and finished it, a rare feat for a first-timer, let alone one who trained only a few times a week in the dead of night.

Jenny's treatments continued, through when the TreeHouse board decided that it was time to bring in another retail pro--a former CEO of video-game mall chain GameStop. "Congratulations, Jason," Ballard says they told him. "You've done a great job, and we're right on the cusp of being able to raise a lot of money and take this thing wide. We think it's an inflection point where we need an experienced retail operator." Ballard would become president, they told him­--"the innovative visionary, focusing on new products, developing new programs."

Ballard was excited about some of it--like developing the home-consultation app he'd dreamed up that could scale TreeHouse beyond its store locations. But mostly he was crushed. "It felt like Moses dragging the Israelites across the desert," he says, "and right when they're about to go into the Promised Land, Joshua gets to take over."

But he had one idea that he wasn't sure would fit with TreeHouse. About a year earlier, he and Loomis had started building a wooden prototype for a large-scale 3-D printer. As TreeHouse had underscored Ballard's earlier doubts about the highly inefficient construction business, he had latched onto 3-D printing as a solution: It would be cheaper, faster, and more resilient in the face of extreme weather and the march of time. He'd read extensively about the potential for 3-D-printing houses and knew that nobody had cracked that opportunity yet. In 2017, he and Loomis joined forces with Alex Le Roux, a freshly minted engineering grad, who was experimenting with the technology in Houston.

Ballard had cultivated the TreeHouse idea while pursuing seminary years before; now he was cultivating Icon while pressing on at TreeHouse. After a full day of work but before his late-night runs, he, an exhausted Jenny, and the kids would spend a few hours working on the printer, the kids screwing beams together. "It still seemed like science fiction," she remembers. "We didn't know if it was going to work. But how fun that we were trying."

But Ballard was already thinking the transformative and financial potential of his new idea was much bigger than TreeHouse's. "We always thought TreeHouse might one day become as big as Whole Foods," he says. (Which is very big: Amazon bought the grocer for nearly $14 billion.) "But it's incremental, not transformational. Icon could change construction and offer shelter for people in desperate need. It would create something that could change humanity."

As Ballard, Loomis, and Le Roux had their first conversations with potential investors, they kept hearing one thing: Icon sounds exciting, but, well, it still seems like science fiction. They needed a prototype printer that could print something that not only looked like a home but was a real, government-permitted, occupiable house. When no funding materialized, the partners maxed out several personal credit cards to build Vulcan I.

Providence came in the form of a chance connection. The founder of Praxis, a Christian startup accelerator that Loomis went through in the early TreeHouse days, introduced him and Ballard to another Praxis alum who'd founded a California-based nonprofit called New Story, whose mission is to build homes for the billion-plus people who lack adequate shelter. New Story provided funding for Icon to complete its printer and build a prototype house. "Aside from climate change, there is arguably no greater emergency on earth today than the housing crisis," says New Story CEO Brett Hagler, who co-founded the charity after Haiti's devastating earthquake in 2010. "To have the biggest impact, we needed a breakthrough to cut costs and build faster without sacrificing quality."

Ballard saw it all as "a way to kill two frogs with one stick"--line up an early partner and some funding while showing potential investors that Icon could create a fully permitted home. So rather than printing something in a cow pasture outside of town, he printed behind a friend's office in a mostly residential area near downtown Austin. They set a goal of unveiling the house at SXSW in March 2018.

A week before SXSW, the Icon team had a working printer and a proprietary concrete recipe--a tricky thing, it turned out, because the concrete has to flow easily through the printer but emerge in solid form, and do so in wildly variable weather conditions. But the "material-delivery system," which loads the concrete into the printer, wasn't working yet. March is the start of Austin's rainy season, and 2018 was no exception. Every night for a week, in the pouring rain, Ballard, Loomis, Le Roux, and a rotating cast of friends working for free beer spent their nights heaving buckets of freshly mixed concrete, by hand, into the printer and extruding a 350-square-foot house.

They finished printing the first day of the festival, a Friday, and spent the weekend installing windows and doors, painting, and hooking up the power and plumbing. The house was finished Sunday night, just hours before their planned launch event on Monday. Total cost: $40,000, and 50 hours of printing time. A city inspector came out and gave the house a temporary certificate of occupancy. An exhausted Loomis hired a friend (now Icon's software lead) to build a quick single-page website that night--a picture of the completed house with a simple contact form for anyone interested in learning more.

Then came the flood of media reports, and countless inquiries from investors, homebuilders, nonprofits, and far-flung governments. Within a month, Icon had requests to build more than a million homes. Portnoy, the former PayPal executive, had been visiting family in Houston while the SXSW media crush was happening; after reading a news story about Icon, he piled his wife and kids into a rented van and drove straight to Austin to meet Ballard and the team at the house, where they sat on the porch and got to know one another.

"It was clear within a few minutes that Jason was the right person to be CEO," Portnoy recalls. "He has such a clear vision of what he wants the world to look like and what he wants Icon's contribution to that vision to be. And he's unapologetic about it: 'This is what we believe, this is what we are going to do, if you want to be a part of it, that's great, and if not, that's great too. We know where we are going.' " In his PayPal days, Portnoy worked closely with Elon Musk, Max Levchin, and Reid Hoffman. Ballard reminded him of them. "They believe in what they're doing with every cell in their bodies. And that conviction imprints on the people around them, who start to believe what they believe."

After the blockbuster debut at SXSW, Ballard wrote a hasty strategy memo outlining two possible business models--selling homes or selling printers--and promptly quit his job at TreeHouse. Months later, late one night that December, Ballard awoke to a call from one of his former executives: TreeHouse was folding. The announcement was going out in the morning. Ballard got out of bed, drew himself a bath, and just sat there, quietly processing the end of the company that had taken him from the priesthood and steered him toward a different kind of service.

He didn't have much time to reflect. By then, he'd set an aggressive goal for Icon to unveil Vulcan II at the next SXSW. The new printer would print 2.5 times faster than the first one. It would be controlled by a simple interface on a tablet computer, the material-delivery system would work, and it would be able to print a 2,000-square-foot building in as little as a few days. Meanwhile, HUD secretary Ben Carson visited Icon. Fannie Mae called. So did FEMA and the U.S. Army. Other officials in Washington alerted Ballard that rival countries were trying to obtain Icon's technology secrets. ("I can't say any more about that," Ballard says.)

On March 11, 2019, Ballard stood on a stage at one end of Icon's hangar-like headquarters and delivered a rousing sermon about the need for cheaper, faster, and better homebuilding to a packed room, and then issued the command to lift a black veil and reveal the hulking new printer, as Steve Jobs once might have.

The cocktail hour that followed felt like a victory party. Austin's mayor and other luminaries grinned and congratulated the Icon team, while a publicist frantically arranged media interviews with Ballard, who'd donned his white cowboy hat after leaving the stage. But Icon had arrived only at the starting line.

The Vulcan II, silent but for the rumble of a small gas-powered generator and an occasional hiss and click, scoots its preprogrammed route around the slab foundation at Community First, eerily snaking out its gray, tube-shaped layers of concrete. The walls of the community center rise almost magically and reach their full height within two days, until, when the building is all but done, at midnight on a Friday, the generator fails. Its primary gas tank has run out of fuel, and its auxiliary doesn't switch on. If the team doesn't fix it immediately, the concrete in the tubes will harden and ruin the printer. Ballard spots a bulldozer, races over, siphons out some diesel the old-fashioned way--with his mouth--and gets the generator working long enough to clear out the concrete. "Luckily, we have a CEO from East Texas," he cracks.

The earlier concrete problems, the team learned, stemmed from a supplier's improperly formulated batch. Once the new shipment arrived, after about 10 days of downtime, things worked again. But Icon aims one day to have third-party builders using its technology all around the world, and when that day comes it will inevitably have to rely on a patchwork of suppliers. Inconsistencies will happen. And if those inconsistencies brick the expensive printers or create misshapen, droopy messes, the promises of revolutionary advances in affordability, speed, and resilience will mean little.

Ballard is unfazed. To him, the slowdown is just one more natural step on his journey, a minor mishap in the grand scheme--the kind of thing that simply informs his next moves, like a new quality-control step in the concrete supply chain. "It's so fortunate that you got to witness that," he says.

There are real-world implications, though. The partnership with New Story is in a new phase: The nonprofit has arranged for Icon to print an entire community of 50 small homes in a mostly rural part of Mexico. That project, the world's first 3-D-printed neighborhood, was originally slated to get under way in midsummer. Now, the delays mean it will start in the fall.

"This feels like a miracle, does it not?" Ballard demands of the crowd. "We will show the world there is a better way, and that way is love."

By early September, Ballard and a few members of the 25-person team he hired in the previous year are living in Mexico, laying foundations for the homes, working to get their giant robot through customs, and girding for whatever unexpected events might befall them next. Jenny, now about 18 months cancer-free, will soon join him and bring the kids.

But on September 10, Ballard is back in Austin for a few days to unveil the completed community center, now painted gleaming white and standing alone in a dirt clearing like a temple. The temperature hits 100 degrees as Ballard steps out onto the concrete porch to address the hundred-some attendees. A lot has happened. In addition to the Mexico project, the company will soon begin printing six homes for the homeless at Community First. It's finalizing a deal to print middle-market homes in Central Texas at 30 to 50 percent below market rates. The ink is still drying on a grant from the Air Force to explore printing facilities for it, and a deal with NASA looks imminent: The agency wants to enlist Icon to help it build on Mars.