Mr. Holliday of Factory OS started thinking about modular housing about four years ago, when he was struggling to build a project in Truckee, Calif., a mountain town of about 15,000 people near Lake Tahoe. The idea was to build a cluster of 800 to 1,000 high-density apartments and condominiums, but "the numbers wouldn't work," he said. "You couldn't get the construction costs down enough."
Mr. Holliday floated the idea of modular building to his longtime contractor, Larry Pace, from Cannon Constructors, who over the past four decades has built various projects from one-off homes to high-rise condo and office towers. "I said 'modular jobs have been a fiasco — we don't need that in our lives,'" Mr. Pace recalled, adding an expletive for emphasis.
But Mr. Holliday persisted, and he and Mr. Pace used modular technology from two manufacturers to build four projects in the Bay Area. They are planning to do the same with the original Truckee development. Mr. Pace became so comfortable with modular that he suggested that they find some investors and build a factory of their own.
On a recent afternoon, Mr. Pace laid out the factory's process. At the first station, just past the door, four workers toiled above and below a raised platform to build what would eventually become the floor. The two men up top laid down flooring while a man and woman stood below simultaneously installing pipes.
From there the unit would move steadily down the line, and, over 21 additional stations, would acquire toilets, indoor walls, outdoor walls, a roof, electric outlets, windows, sinks, countertops and tiling. It takes about a week to finish a unit, Mr. Pace said. The goal is to churn out about 2,000 apartments a year, which would be turned into four- and five-story buildings with 80 to 150 units each.
For workers, factory building seems to mean lower wages but steadier work. Factory OS pays about $30 an hour with medical insurance and two weeks of vacation. That's about half what workers can make on a construction site, but the work is more regular and, for many, requires less commuting.
Tony Vandewark, a 51-year-old foreman at Factory OS, is OK with the trade-off. Mr. Vandewark lives a few minutes from the factory in Vallejo, where homes cost less than half what they do closer to San Francisco. Contrast that with a job he once had in the Silicon Valley city of Sunnyvale. Mr. Vandewark drove two hours to work and three hours home before deciding to rent a room so he could stay closer to work on weekdays.
"On a job site, you can go do piece work and make really big money, but then the job is gone," he said.
In addition to not being rained on, one of the key differences between a construction site and Factory OS is that any worker can be trained to do any job. And for old-school trade unions, that is a declaration of war. "The business model is 'Hooray for me,'" without regard for anyone else, said Larry Mazzola Jr., business manager of UA Local 38, a San Francisco plumbers' union with about 2,500 members across Northern California.
Factory OS is not anti-union: It has a contract with the Northern California Carpenters Regional Council, which has organized other modular factories and is banking on the technology's continued growth. The issue is that builders are laid out like a Detroit auto factory, where one union represents all of the workers, and workers can be trained to do any job within the company walls.
That is a huge departure from construction sites, where unions representing plumbers, electricians, carpenters and various other trades each control their piece of the building process. Last year Mr. Mazzola wrote a letter to San Francisco's mayor, Ed Lee, a month before he died, urging him to deny any city business — such as contracts for subsidized housing — to Factory OS.
"Any decision to use Factory OS shows a blatant disregard for the other craft unions," he wrote. He asked the mayor to refrain from contracting with the company unless it allowed craft unions to do their pieces of the work. "We realize modular is coming and we want to be part of it, but not at the expense of our workers, which is what's happening right now," Mr. Mazzola said in an interview.
Jay Bradshaw, director of organizing for the carpenters' council representing Factory OS workers, said that would be impractical. Think back to that first station, where four people worked above and below the floor. In Mr. Mazzola's world, a plumbers' union would represent the workers installing pipes, while other unions would represent the workers up top.
"It would never work to have upward of 10 or 15 labor organizations at a single employer in a factory setting," Mr. Bradshaw said.
For Mr. Bradshaw, the real fight isn't defending job titles but making sure construction workers remain part of a union at all. A short drive from Factory OS, at a carpenters' training center, the union is developing a program to train housing-factory workers — something that, it hopes, will prepare more people for an industry that it has come to see as inevitable.
"It sure blows the hell out of building in China," he said.