Abstract: A panel element for use as a roof tile or other building element, e.g. on a vertical surface, is molded in one piece and includes upper, lower and left and right marginal edge regions. To facilitate securing the panel in place, the upper edge region may include fastening apertures. The lower marginal edge region of each panel is secured to the upper edge region of another panel in a lower row of panels. For this purpose, interlocking formations are provided in the upper and lower marginal edge regions, with the locking formation in the upper marginal edge region being below the nail apertures. This locking formation can serve both to prevent water travelling up to the nail apertures and as a locking formation. Support ribs under the panels can provide both uniform support from an underlying planar surface, and can also form the locking formations. The panel can be molded in any suitable material to simulate a variety of known tiles or other building elements.