This inventions is a prefabricated roof plate element (6) comprising load carrying girders including longitudinal upper and lower steel frame parts placed at opposed sides of the roof plate element. The girders are corrugated at opposing upper and lower sides in the longitudinal direction at which vertical side walls of the steel frame parts are interconnected connection plates which are part of the load carrying girders. The lower steel frame parts (4) preferably are interconnected by an integral steel panel part (8) forming the bottom of the roof plate element and a ceiling of a building. The prefabricated roof plate element has uniform roof plate elements (20, 54) which are interconnected side by side, to form a wider prefabricated roof plate element. Cavities thereof are filled with insulation material and afterwards provided with a common top plate construction (70, 72) and a common roof foil covering (74).