    Sentence 1: Working versions of 3D-printing  building technology are already printing how  much building material per hour?    Sentence 2: Working versions of 3D-printing  building technology are already printing 2  metres (6 ft 7 in) of building material per  hour as of January 2013{update], with the  next-generation printers capable of 3.5  metres (11 ft) per hour, sufficient to complete  a building in a week.