3D printers have been around for decades — think engineers making plastic prototypes of car parts or architects printing small-scale models of buildings. But what about 3D printing the buildings themselves — full-sized houses — using concrete instead of plastic?

Well, a number of companies are doing just that. 

From inside his garage, Jim Scott demonstrated a 3D printer that can build the concrete walls of houses.

“That back-and-forth motion is what the printer does,” Scott said. The prototype took up most of the space in his four-car garage in Colorado Springs, Colorado.  

“It starts at the bottom and then it goes up, up, up, up, up,” he said.

Scott’s company, called StructureBot, is one of several trying to disrupt the housing industry. It’s a tech company designing products for construction companies to purchase, like that giant printer.

The prototype consists of a 16-by-16-foot steel scaffolding supporting a robot holding a silver cistern with a nozzle. The nozzle lays down layers of specialized concrete a couple of inches wide. The result is a wall that looks kind of like concrete corduroy.

It could be a game changer in the world of affordable housing. Cheri Witt-Brown, CEO of the Habitat for Humanity chapter in Greeley, Colorado, has been following this technology for a while. 

“For the first few years it was a little bit more expensive, clumsy, maybe not cost-effective enough for affordable housing,” Witt-Brown said.

But when she recently had the chance to tour some 3D-printed houses, she was blown away. 

“I’ve been in this business for over 37 years, and it’s the first thing that’s come along that I think … will revolutionize the industry,” she said.

She said “revolutionize” because those concrete walls can be printed in hours, versus the days or weeks it can take to frame a traditional home. They provide great insulation and can cut a household’s energy bills in half.

3D-printed walls also tend to be stronger, easier to maintain and more resilient against natural disasters — especially important in wildfire-prone Colorado.

“With 3D-printed homes, you’re looking at something that is much more fire-resistant,” Witt-Brown said.

At the same time, the houses look basically like any other single-family home, just with those corduroy-textured exterior walls.

Habitat for Humanity plans to build up to 15 of these homes in Greeley next year, and it hopes to add dozens more after that. It’s contracting with a builder called Alquist 3D. Founder Zachary Mannheimer moved his company to Colorado and wants to make it an epicenter for shaking up home construction.

“This industry is overdue for advancement, and that’s what this technology is trying to do,” Mannheimer said.

Along with the Habitat contract, Mannheimer said Alquist is working with a local community college to create a first-of-its-kind 3D-building curriculum.

“Once you go through that program, you’ll be certified to be a 3D printer, and companies like ours will hire you,” Mannheimer said.

3D-printed concrete is really only used for making those corduroy walls. Roofs, trusses, all the rest, that’s still done the traditional way, at least for now.

Alquist homes currently cost about the same as a standard lumber-built house. But, Mannheimer hopes to drop the price by as much as 30% as his company scales up.

“We’re not there yet today. But within the next 24 months, we believe we will be,” Mannheimer said.

If all these benefits pan out, Mannheimer believes 3D printing could put a real dent in the country’s affordable-housing crisis.