Rising from each track was a metal tower, and connecting those towers was another perpendicular track of sorts, with a machine sliding across its rails from side to side.
For the past few months, one vertical inch at a time, that machine glided up, down and across its gantry system to create the high-ceiling, single-story home before it.
Soon it will glide to the next parcel of the subdivided lot, where inch by inch the process will repeat, forming a row of five concrete houses in what its developer has called the first micro community of 3D printed homes in California.
The five-home community under construction by 4dify, a Sacramento -based developer, using technology acquired from New York -based SQ4D, serves as a test-run for future homes and communities built from 3D printing, a novel building method with potential to blossom in housing-crunched California.
“Long term, we definitely want to be a leader in the industry,” said Nan Lin, Sacramento developer and 4dify owner. “Short term, we want to dial this in for the next few houses and we want to start scaling this.”
Proponents of 3D printed construction boast the potential for the technology to build housing more efficiently — particularly at scale — while lowering costs, saving time and reducing waste when compared to traditional home building methods.
The trend of building 3D printed homes has taken off in other parts of the country, including Texas, where the technology has been used to develop communities as large as 100 homes, according to various media outlets.
In California, the first 3D printed homes were built several years ago in Redding by Emergent 3D. The partnership between 4dify and SQ4D differs in terms of the design and functionality of its 3D printer, and scale, with plans to deploy multiple machines simultaneously to build out larger developments.
The five homes under construction in Yuba County , designed by Endemic Architecture, provide a test run, using the large machine to build a relatively small community of modest-size homes before tackling more ambitious projects.
The Sacramento developer next plans to use the machine to build 19 units, which are currently in the design phase, in Sacramento. Lin said that his company has also signed on to a project of 75-100 3D printed duplexes, which is still in its early stages, in Southern California.
A New Way to Build
A crew of workers outside of 4dify’s first 3D printed home on the Yuba County lot this week was plastering a stucco mixture to the home’s outer walls. That job is not uncommon to a traditional home build, but with the 3D printing machine, the manner of applying and smoothing the outer base layer was far from ordinary.
An attachment to the machine sprayed the plaster, specifically mixed on-site and fed to the printer, covering large swaths of the walls and accelerating the time needed for the task.
“We want the machine to do the heavy lifting,” Lin said. “We want the humans to do detailed work that the machines can’t do yet.”
The 3D printer set up has several components.
A portable silo holding the cement powder and materials funnels them to an adjacent machine — controlled by a worker — that mixes the cement, allowing the builders to batch their own concrete and control its consistency and thickness as needed. Batching the concrete themselves costs roughly a third of the price of buying and having the concrete mixed, Lin said.
Another worker operates the machine’s main controller, using a programming scheme for 3D printers called G-code to tell the printer what to build and how to build it. The nozzle pours a thick stream of concrete while gliding precisely on its course, stacking each layer, one after another, about an inch thick.
“It is extremely accurate,” Lin said.
In 24 days the machine layered the 1,000-square-foot house 13 feet high. That timeline was slowed due to “bureaucracy” and the newness of the technology, Lin said.
The next two homes in the micro community will be built simultaneously with the same machine.
Lin said that with the machine, which cost about $1.5 million, he expects to eventually have crews of three to five workers each building a house every four to six weeks, rather than a crew of five to 10 people building one over the course of several months.
With one machine capable of printing eight to 10 houses in a year, Lin said that he plans to scale up to having 10 machines building up to 100 houses per year.
The three bedroom, two bathroom homes in the Yuba County micro community have not yet posted for sale, but Lin said he expects to list them in the ballpark of $350,000 to $375,000.
Why Concrete?
Beyond the efficiencies for developers, proponents of the new building method tout cost-savings and durability advantages for the people who choose to live inside the robot-built houses.
“Concrete is a super well understood material that’s used across the world for a lot of different projects, and it doesn’t have the same issues as wood,” said Kristen Henry , SQ4D chief technology officer. “So it’s a really good building material that’s strong, durable and weather-resistant in light of a lot of the changing climate things going on.”
The concrete base and walls make the homes more resistant to fire and other natural elements, and could provide significant energy savings when heating and cooling the houses. The homes in Yuba County will have metal roofs supported by wood trusses. But future designs may allow for the 3D printer to create a concrete roof, removing anything flammable from the home’s exterior.
“It’s water, fire, wind, mold, pest, people resistant,” Lin said. “You can’t punch a hole through the wall. If this was a rental product, it would last so much longer than a traditional product.”
Samples of the Yuba County home’s walls even withstood ballistic testing, Lin said, as they were taken to a range and shot with guns multiple times.
“They’re bulletproof,” he said. “The bullet just stops on the wall.”
From a design standpoint, the SQ4D printer helps streamline the electrical and plumbing processes that typically require different work crews to complete. In addition to interior and exterior walls, the machine also creates a slab foundation and footings, Henry said, which differentiates it from other printer designs.
“Traditional construction is very wasteful, a lot of materials end up going to the landfill so we’re really hoping to cut down on that because we’re using concrete to calculate the exact amount of material we need before the project begins,” Henry said.
The waste generated by the 3D printed builds is deposited into casts resembling large Leggo bricks. Once full, a solid block can be removed from the mold and used for practical purposes, such as retention walls.
Addressing a Housing Shortage
The development fits into the broader push by Yuba County officials to expand housing supply in the rural county north of Sacramento.
“This is definitely a first of its kind for us in Yuba County and something where our building team and community development team as a whole has had to do some outside of the box thinking,” said Ashley Potočnik, Yuba County business engagement manager.
The permitting process went smoothly despite the relatively new form of construction, Lin said. The build was subject to special inspections, which entailed the county sampling the concrete mix each day the machine was operating, similar to inspections used for commercial projects.
Much of the new housing in Yuba County has been developed south of Marysville and Olivehurst, with areas such as Plumas Lake continuing to add subdivisions, and active construction sites visible from parts of Highway 70, an artery connecting the county to Sacramento.
“It is redevelopment, which is great,” said Gary Bradford , Yuba County supervisor, of the 3D printed micro community. “It’s adding density, which is also great, and helping to revitalize an older, lower income part of the county.”
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