STAIRCASE

series, or flight, of steps between two floors. Traditionally staircase is a term for stairs accompanied by walls, but contemporary usage includes the stairs alone. The origin of the staircase is uncertain. On the road up Tai Shan (mountain) in China there are many great flights of ancient granite steps; the earliest staircases seem to have been built with walls on both sides, as in Egyptian pylons that date from the 2nd millennium BC. The Cretan palaces, as at Knossos and Phaistos (both c. 1500 BC), make important use of stairs, and the Assyrian ziggurat of the 9th or 8th century BC was often adorned with massive stairs. The palace terrace at Persepolis has a double flight of steps (6th century BC) of great beauty. The Romans were noted for their monumental sense in the use of stairs, a conception that has marked architectural history until the simplification of the 20th century. The use of steel and of reinforced concrete has made possible the daring curves and fantastic sweeps that can be important features in contemporary design. Staircases have traditionally been built of wood, stone or marble, and iron or steel. The horizontal surface of a step is called its tread and the vertical front its riser; steps are placed between strings that are inclined to the angle of the staircase; strings are supported by newel posts that also support the handrail, forming a balustrade.