Claesson Koivisto Rune's Plus House took 40 days to build: 20 in the factory and 20 onsite. CKR's mode of prefabrication is about not building modules but panels: Girders, walls and trusses are assembled before delivery. Finding a vacant lot in Stockholm isn't easy; though not so central, this plot has fresh air and estuary views.  The Best of Prefab: 7 Homes We Love by Diana Budds