It would use a movable gantry taller than the house you want to build. Concrete pours out and is set down layer by layer, like a typical 3-D printer would sinter plastic together. It could be ideal for emergency housing, commercial or low-income structures, but it could also be used to print out customized luxury homes, according to Khoshnevis. Or, he adds, it might be ideal for the moon or Mars. "Contour Crafting technology has the potential to build safe, reliable, and affordable lunar and Martian structures, habitats, laboratories, and other facilities before the arrival of human beings," his website reads.