Abstract: A sealing strip is provided which is suitable for sealing flat roofs and engineering structures at outer corners. The sealing element is made of a weather-resistant elastomer or plastomer and comprises, in a zone positioned intermediate its ends, at least one pair of areas in the form of oppositely directed waves whose amplitudes and wave-lengths increase regularly from the center line of the strip towards its longitudinal edges so that said zone comprises a planar basal surface and an additional curved a planar sectorial surface corresponding to each wave. The wave-shape areas enable the sealing element to be smoothly laid around an outer corner without straining any areas of the strip.