An edge beam construction including two vertical perforated rolled shapes with webs inverted toward the center of the beam, and a bottom track having a flange disposed in a vertical position against bottom lips of the vertical rolled shapes. The three basic components of the edge beam are positioned so as to provide access for press joining tools. A building module manufacturing method utilizes the light gauge steel rolled shapes that permit industrialized, automated manufacture of floor, roof and wall panels for modular housing and commercial structures with integrated mechanical and electrical systems and rigid framing for road transport without trailers. The module manufacturing method includes a novel method of constructing and positioning a gable.