Abstract: A box-shaped, self-supporting building unit, a plurality of which may be arranged juxtaposed and/or superposed for the construction of a building, the unit including a self-supporting floor element and a self-supporting ceiling element, both having a supporting structure, and two pairs of opposite wall elements as well as a supporting, vertical column of sectional iron in each corner, the column rigidly connecting the supporting structure of the floor element with the supporting structure of the ceiling element.