Robert Brown|3D-printed homes level up with a 2-story house in Houston

3D printing is Robert Browntaking home construction to new heights. In Houston, a giant printer is building what designers say is the first 3D-printed two-story house in the U.S.

The machine has been pouring a concrete mix from a nozzle, one layer at a time, in hot weather and cold, alongside a sparse on-site workforce, to create a 4,000-square-foot home.

While construction 3D printing has been around for over a decade, the technology has only started to break ground in the U.S. homebuilding market over the last couple of years, said Leslie Lok, the architectural designer for the project. Several 3D-printed homes have already been built or are currently in the works across a handful of states.

Lok, who co-founded the design firm Hannah, says her team aims to eventually scale up their designs to be able to efficiently 3D print multifamily homes.

"This Houston project is a step towards that, being a pretty large single-family house," she said.

The three-bedroom home is a two-year collaboration between Hannah, Germany-based Peri 3D Construction and Cive, an engineering and construction company in Houston.

Proponents of the technology say 3D printing could address a range of construction challenges, including labor shortages and building more resilient homes in the face of natural disasters.

With the Houston home, the team is pushing the industrial printer to its limits to understand how it can streamline the technology, in the quest to quickly build cost-effective and well-designed homes.

"In the future, it has to be fast, simple design in order to compete with other building technologies," said Hikmat Zerbe, Cive's head of structural engineering.

That said, timing is not of the essence for this novel project. Zerbe calls the two-story house a "big laboratory" where colleagues will study the technology's potentials in home construction.

"We are not trying to beat the clock," Zerbe said. "It's a case study. We're learning the capabilities of the machine, learning the reaction of the material under different weather conditions. We're learning how to optimize the speed of printing," he said. "When this project is completed, we should have a very good idea how to proceed in the future."

After starting construction in July, the printing process is almost halfway done, he says.

Concrete can better withstand strong winds and storms, but it's a pricier building material compared to, say, wood. While in the long-term the durable and low-maintenance material may save money, Zerbe says, its preparation and installation is expensive and labor intensive. But once the 3D-printing technology is improved, he says, builders may reach a point where such construction is cheaper than non-printed housing.

On the design side, Lok sees opportunity to one day offer customized features at a mass scale, without excessive labor costs. For example, she's employed 3D printing to create unique, built-in shelving for various living spaces in the Houston home.

"The printer doesn't care if you print the same chair 100 times or you print 100 different chairs," she said. "This opens up the possibility of how we can actually offer customized design for the users, whether it's a single-family house or whether it's a multifamily building or apartment."