On this loud, lively Habitat for Humanity of Central Arizona building site in Tempe, Arizona, power tools grind and whir, and construction workers and yellow-shirted Habitat volunteers briskly walk from one job task to another. At one part of the site, large green lights top an elevated steel mast; everyone on the site dutifully notes them, as they would a traffic signal. At intervals, a loud flat sound cuts through the construction clamor and the green lights blink. Immediately, a BOD2 gantry printer designed and built by the Danish construction company, COBOD, begins delivering Laticrete®, a proprietary cement, through a steel head that travels along the wall alignment and makes pinpoint corner turns as it creates Habitat for Humanity’s first 3D-printed home in the United States.
As the gantry moves along both x and y axes of the walls and vertically to complete columns, the head outputs the high-strength cement until each section is complete, placing it as meticulously as a printing press does ink on paper. A technician posted next to a large delivery hopper issues commands through a hand-held control unit; the lay-down is spot-on.
“When the green light is on, that means the walls don’t need material, and when the blinking begins, the software delivers the Laticrete,” says Steve Horst, director of construction for Habitat for Humanity Central Arizona.
Habitat’s President and CEO, Jason Barlow, and his team have partnered with the Shivers family, who plan to move into this historic 1,738-square-foot, three-bedroom, two-bathroom home designed by award-winning Scottsdale architects Candelaria Design Associates. As with all Habitat for Humanity families, they have agreed to make their “down payment” with 400 hours of sweat equity, Barlow explains.
Three other traditionally built homes will complete the one-acre site, purchased by Habitat Arizona at a nominal cost from the City of Tempe, a longtime project partner. Other participating businesses in the printed home include the PERI Group, 3D Construction, The Brewer Companies, Chas Roberts, Younger Brothers, Lowe’s, Cox Communications, Ramsey Social Justice Foundation, and many more.
The Arizona group is aligned with Habitat for Humanity International of Americus, Georgia, founded in 1976 by Millard and Linda Fuller on a farm owned by Clarence Jordan. Supported by well-wishers such as former U.S. President Jimmy Carter and his wife Rosalynn, Habitat now works in all 50 states in the U.S. and in 70-plus countries. As a result, more than 35 million people have achieved safe, decent, and affordable shelter.
In turn, Habitat Arizona, coordinating with local firms and volunteers, has built more than 1,170 homes, assisted in 2,500 repairs, and improved the lives of 3,800-plus Arizona families since its founding in 1985.
“This is really a moonshot opportunity for Habitat for Humanity. When we consider the housing issues facing Arizona, the need for affordable homeownership solutions becomes clear,” Barlow says. “If we can deliver decent, affordable, more energy-efficient homes at less cost, in less time and with less waste, we think that 3D construction will be a real game-changer. Think of the implications.”
A FUTURE OF POSSIBILITIES
Most of the 3D home at 677 W. 19th St. will be printed—about 70%–80%—including the internal and external walls. The remainder of the house is built traditionally, Horst explains. Once the printed walls are complete, the construction team will complete the wood truss roof, add insulation and shingles, ceilings and floors, a garage door, doors, and windows. Because of the gantry method, the printer can move to any position within the structure, putting down both inner and outer walls layer by layer. So, too, as this structure moves from one area to the next, manual work, such as laying empty conduits and connections, can be easily integrated into the process.
Although printed, the home will be strong and provide excellent sound attenuation, Horst says. “We took core samples of the cured cement and tested them to 10,000 psi; we believe that means the walls are capable of withstanding up to 120-mph winds, equal at least to most stick-built homes.” He notes that PERI is working with groups such as the International Building Council to certify 3D printing. For the home’s designer, Mark Candelaria, structural printing “opens up endless possibilities. We can create and construct both repetitive and custom structures with less labor and less waste, thus bringing the time and cost of producing a house down,” he says.
In 1999, he founded the high-end residential architecture firm which now includes three partners, Vivian Ayala, Meredith Thomson, and Evelyn Jung. Damon Wake, an associate architect, partnered with Candelaria on the 3D home design.
Candelaria is a Habitat Arizona board member. A little more than a year ago, Paul Mooney and Clarence McAllister from 3D Construction of Phoenix suggested to the board the opportunity of building Habitat for Humanity’s first 3D-printed home in the Valley. Connections were made with the PERI Group in Germany and structural engineer, Dominic Petrocelli, of PH Structural in Mesa.
“We adapted one of the already existing and often-constructed Habitat plans to use with this state-of-the-art 3D printing technology,” Candelaria recalls.
Progress has been swift. The Habitat team pulled permits in March of this year, PERI shipped its 3D printer to the U.S. that month, and it was transported to Arizona in April. Printing began in May. 3D future construction is sustainable.
“Because the walls of the home are printed in concrete versus frame, there is virtually no waste. Just like the printer you use to print your documents, only the ink that goes down on the paper is used, and it’s the same with the concrete,” Candelaria explains.
“So many of our typical tract homes including our Habitat homes are built of wood-frame construction, requiring trees to be cut down, and so much of the lumber waste ends up in landfills,” he adds. “The concrete is made from sand, gravel, cement and water, thus also requiring less upkeep, maintenance, and hopefully extending longevity, all adding to the sustainable aspect of this kind of building.”
Dorie Morales, publisher of Green Living magazine in Scottsdale, adds, “The first 3D-printed home in Tempe is an innovative and sustainable way to expand affordable housing. The project is very exciting because of the technology, reduction of waste, time and manpower and affordability. Habitat for Humanity Central Arizona partnered with many groups that have donated their time and resources to make this home possible. The house will be solar-ready, and is pursuing a LEED Platinum certification, which is for the good of our planet.”
AFFORDABILITY AND ACCESSIBILITY
When it is more widely used, the 3D construction model will also cost less than traditional construction methods. In addition, the technology can be used for homes as well as multifamily residences at any price, says Thomas Imbacher, managing director of innovation and marketing
for the PERI Group, one of the leading manufacturers and suppliers of formwork and scaffold systems in the world.
Since 2016, PERI has developed 3D construction printing solutions for residential construction. In 2020, the company built the first 3D-printed house in Germany with a BOD2 printer, followed shortly after by the largest 3D-printed apartment building in Europe to date. And, just recently, the firm won the German Design Council’s German Innovation for a 3D-printed two-story home in Beckum, North Rhine-Westphalia.
“Our PERI 3D construction printing team is incredibly proud to print this home in Tempe for Habitat for Humanity,” he says.
For Tempe Mayor Corey Woods, Habitat for Humanity Central Arizona’s 3D home aligns with a municipal goal to find new solutions to develop affordable and workforce housing inside the city. While Tempe, anchored by Arizona State University, has many affluent areas, it also has some neighborhoods with high poverty rates.
“We have to make sure that anyone who wants to live here, including my 82-year-old retired dad, has that opportunity,” he says.
Habitat Arizona and the City have partnered for more than 30 years; in addition to the 3D home, 15 traditional homes are now also in process on four city lots.
Woods recalls that when he was in his 20s, he had to stretch to make his mortgage payments, but some friends had to leave the city.
“We must be committed to not losing our intellectual capital because we can’t provide affordable housing,” he says. “When I became mayor in 2020, I pledged to make that part of my mission, and this historic Habitat for Humanity project suggests that, working together, we can get that done.”
To learn more, visit www.habitatcaz.org/3D, www.3dconstructionusa.com, www.candelariadesign.com/3d-printed-home-for-habitat-for-humanity-az, and www.tempe.gov.