http://www.txchnologist.com/2012/printing-a-home-the-case-for-contour-crafting
QuoteIt can take anywhere from six weeks to six months to build a 2,800-square-foot, two-story house in the U.S., mostly because human beings do all the work. Within the next five years, chances are that 3D printing (also known by the less catchy but more inclusive term additive manufacturing) will have become so advanced that we will be able to upload design specifications to a massive robot, press print, and watch as it spits out a concrete house in less than a day. Plenty of humans will be there, but just to ogle.
.. more at link.
http://www.youtube.com/watch?v=JOlRI_Hm1Po
I'm sure Hewlett Packard will practically give away the extrusion tool "printer," but they'll make up for it on the proprietary "ink" cartridges!