Abstract: Combinations of inorganic corrosion-protection, passivating chemical treatment, and selected organic-type coatings of flat-rolled mild steel of selected thickness gauge and mechanical properties, provide for fabrication of composite-coated unitary sheet metal structures for lightweight and durable roof covering. Weathertight features with provisions for subsurface air circulation, free of liquid from precipitation, are provided by fabricating interfitting slot configurations on four linear sides of a viewable tab portion. Methods of fabrication provide for ease of assembly while providing configurations which compensate for barriers to entry of liquids where linearly-extending slots interfit during horizontally-extended assembly, and provide a horizontally-oriented appearance for viewable tab portions throughout a horizontally-extended assembly of unitary flat-rolled sheet metal roof covering structures.