Abstract: A Lightweight Pre-engineered prefabricated modular Building System comprised of nine pre-fabricated structural members and three prefabricated connectors which create the entire building main frame system. A multiple use principal structural member is utilized as columns and top and bottom cords as well as end rungs for trusses and truss legs. The connectors are right angle connectors; each employing a configuration of holes and slots for securing structural members to create a rigid attachment of rafters to columns. The same connectors can be employed to establish a shallow pitch or a steep pitch roof pitch through selection of the holes and slot positions used to bolt the structural frame together. Trusses are interchangeable anywhere in system. Eave peak members, purlins and girts are used to attach sheathing to the structural frame. Alternatively, a "V" shaped stiffener can be employed with the columns.