The Latin word “membrana”, from which the modern “membrane” is derived, means a “parchment” or “skin”, the main characteristic of which is its thinness. Modern membranes used in building construction as load-transmitting surfaces have to be capable of being tensioned and adopting three-dimensionally curved forms. The thin skin is able to resist only tension loads. Mechanically tensioned membranes should ideally form a doubly counter-curved surface; while pneumatically tensioned systems are usually in the form of doubly curved surfaces in a single direction. Only in this way?can the membrane resist opposing forces, such as?wind suction, wind pressure and snow loading, and transmit them economically and?safely to the primary structure and the foundations. Since the 1950s, the development of plastics technology – especially in the form of composite materials – has led to increasing numbers of innovative membrane projects. Materials of great strength now allow the construction of large-span, translucent roof structures with slender dimensions and without intermediate columns. In the future, one may expect an ever greater use of membrane systems as permanent space-enclosing structures, even under the climatic conditions prevailing in central and northern Europe. (Karsten Moritz)