A building is constructed from a plurality of rectangular wall sections secured to one another. At least some wall sections are formed of an upper and a lower beam, vertical studs extending between the upper and lower beams and a wall panel secured to the beams and to the studs. In the invention, each beam is formed of an elongate metal sheet folded through a right angle about at least one longitudinally extending line to define at least a horizontal first plate, and a vertical second. A plurality of separately formed sheet metal brackets are secured to at least one of the plates of the folded metal sheet at preset distances from one another along the length of the beam and secured to the ends of the studs.