Dozens of families living in El Salvador's slums hope to swap their makeshift wooden shacks for concrete 3D-printed houses next year, in what developers say is the first project of its kind in the world. ICON, a Texas-based construction technology company has unveiled a 33 square metre house, which it printed and built in two days using a gigantic, portable 3D-printer. "Something that sounds like science fiction is real," Jason Ballard, ICON's co-founder, told the Thomson Reuters Foundation. "We plan on printing a whole sort of development .. not just a 3D-print house but a 3D-printed neighbourhood."