Ultimately, it would work like this: On a cleared and leveled site, workers would lay down two rails a few feet farther apart than the eventual building’s width, and a computer-controlled contour crafter would take over from there. A gantry-type crane with a hanging nozzle and a components-placing arm would travel along the rails. The nozzle would spit out concrete in layers to create hollow walls and then fill in the walls with additional concrete, most likely an insulating variety that incorporates polystyrene beads. The placement arm would insert wiring, reinforcing rods, and plumbing and ventilation shafts in hollow chases left in the walls, welding and screwing sections together as the building rises. The arm would then place beams on top of the completed walls to form floors and the roof. Humans would hang doors and insert windows.

“I have other patents, but I always wanted to do something really significant for humanity. It seems this is the one,” says inventor Behrokh Khoshnevis, with his contour crafter.
“You could set it up on a site to build one house or a whole row of houses,” says Khoshnevis. He has even designed a contour crafter that climbs, allowing the construction of skyscrapers.


As smart as the idea of contour crafting seems to be, houses require more than good engineering. They will not be popular if they resemble concrete bunkers more than elegant, graceful homes. Khoshnevis points out that the exterior trowel could be followed by a rolling die that prints a brick, shingle, or clapboard pattern in the wet concrete, while the interior could be painted using ink-jet technology in any color, or even in wallpaper patterns. The concrete itself could be of varying types, including versions that resemble adobe or plaster.

With more complex nozzle architectures, the machine could make buildings that are not just cheaper and quicker to build but far safer too. Today, for example, making a house earthquakeproof is material intensive, expensive, and inexact. But a contour-crafted building “can be strengthened in a smart way,” says Khoshnevis. “The reinforcement steel and even the chemical composition and thickness of the walls could be changed on the fly, with more added precisely where it is needed.”

Some building professionals are enthusiastic. Greg Lynn, a Los Angeles architect who specializes in buildings with curvilinear, organic shapes, was pleased to discover that “this machine doesn’t care if it is doing curves or lines. Living in a rectangle becomes an option, not mandatory.” If a whole-house machine existed today, Lynn says, “I’d be using it right now.”

Khoshnevis believes that the varied shapes created by a miniature version of the contour crafter herald a revolution in architecture. “You will see houses, neighbor-hoods, and cities that look very different,” he says.
“It’s exciting,” says Dennis Shelden, chief technology officer of Gehry Technologies, a Los Angeles building technology research and development company. “This represents the next step forward.” But he cautions that there may be structural issues. “We need to take a close look at how good the bond is between the layers.”

Khoshnevis is confident that won’t be a problem: “The extruded layers can serve as form walls for a filling layer of structural material.” Because that filling layer would be a monolithic slab of concrete, “it will be plenty strong,” he says.

Even NASA seems to be interested. Khoshnevis recently shipped a prototype wall builder to engineers at the Marshall Space Flight Center. They want to find out if contour-crafting technology could erect buildings on the moon from lunar dust.

Here on Earth, what about all those construction workers who would suddenly be out of a job?

“This concern is nothing new,” says Khoshnevis. “When the automobile came along, people said, ‘What will happen to all of those horse-carriage drivers?’ But technology that makes sense typically brings dramatic social changes for the good. This is no different.”

Khoshnevis is inspired by the technology’s potential to build dignified low-income housing. “A billion people today do not have adequate shelter,” he says. Using soil dug from the building site and stabilized with cement, the contour crafter could erect inexpensive dwellings customized to a family’s needs.

“This technology is like a rock that we have rolled to the top of a cliff,” Khoshnevis says. “Just one little push, and the idea will roll along on its own.”