3D printer could build a house in 20 hours
[Philip Lelyveld comment: nothing new here - they are already doing this in Europe, but putting it in a TEDx talk makes it legit.]
The apparatus, instead of being the size of your typical laser printer, would actually be somewhat bigger than the house it would build through a concrete layering system called Contour Crafting.
The professor explained the process in a speech at the TEDx conference, which you can watch. (Start at 4:30 to see the animation demo.) In the video, the professor demonstrates how the machine lays down a concrete foundation, puts up walls, even inserts wiring and plumbing, and eventually constructs an entire building, which Professor Khoshnevis says can be completed in less than a day. (All that's left to add are doors and windows. ) Robotics could even be used to add details like tiles, says the professor.
Khoshnevis doesn't have just efficiency in mind—he wants to end the scourge of slums in the developing world. The system would be right for emergency, low-income, and commercial housing, notes the Contour Crafting website, such as in areas devastated by a natural disaster. Mechanizing home building would be cheaper and more efficient, Khoshnevis argues.
See the full talk and video here: http://news.yahoo.com/blogs/sideshow/3d-printer-could-build-house-20-hours-224156687.html