Abstract: The invention concerns prefabricated buildings built up of transportable prefabricated room elements each being a cell-like structure having four faces and comprising a floor panel, load-bearing columns attached thereto, and a roof or ceiling supported by the columns. In one construction in which the columns are provided at corners of the floor panel, one corner is void of a column so that when the room elements are mounted face to face, with the column-less corners meeting, an unobstructed floor area results. In another construction, a column is omitted at an intermediate point in the length of one face. The room elements are constructed at a factory, and a temporary support is inserted at each location at which a column is omitted. The room elements are transported from the factory to the building site and there assembled face to face into storeys of a building in which the room elements of each upper storey are supported on the columns and temporary supports of the room elements of the next lower storey.