STAIR (O. Eng. stǣġer, step, from stigan, to climb, cf. Ger. steigen; the root is also seen in " stile " and " stirrup "), in architecture, the term (Fr. escalier) given to a series of steps rising one above the other, either in one straight line or with returns, or round a newel, or open well-hole, either square, rectangular, circular or elliptical. A series of continuous steps is called a "flight." The ordinary staircase of two flights with landing between is known as a " pair "; " two pair back " therefore would be the room at the back on the second floor; in houses where the space occupied by the staircase is very limited there is no landing, but the stairs wind round the corner post or newel, and are known as "winders."
The steps of a stair consist of "tread" and "riser," the respective dimensions of which vary according to the importance of the staircase and the space which has been given to it; in external flights or stairs, such as those at Persepolis, the tread is so wide and the riser so small in height as to allow of a horse ascending, and generally in garden terraces there is the same slight rise. For the stairs of a palace or municipal building, 14 in. tread and 5 in. riser would be required, but as a rule 12 in. tread and 6 in. riser is adopted. In the stone staircase in the palace at Cnossus in Crete, the treads were 18 in. and the risers 512 in. In ordinary houses 9 in. or 10 in. is generally given for the tread, and 612 in. to 7 in. for the riser. In the stairs leading to lofts, and in yachts or steamers, the ascent is much steeper, having sometimes 10 in. rise and 5 in. tread. The series of stairs provided to ascend from one floor to another when enclosed with walls is known as a staircase (q.v.). Unenclosed flights of steps placed in front of a building are known by the French term perron (q.v.), usually applied to a structure like the horseshoe staircase of the palace at Fontainebleau, the stairs of which are carried on a support independent of the main wall of the palace. From this point of view the great return flight of steps at Persepolis might be looked upon as a staircase, because on one side the steps are all embedded in the main wall of the platform.
Belonging to the same type are the great flights of steps which led to the successive stages of the Ziggurats or Assyrian stage towers; those in front of the Propylaea, leading to the Acropolis at Athens; the stairs leading to the Propylaea (150 ft. in width) at Baalbek; others in Palmyra; and generally all the Roman temples. In medieval times should be included the great flights of steps which stood in front of the cathedrals of Europe, some of which, as those at Le Puy in France, Ste Gudule at Brussels, the cathedral at Erfurt in Germany, S. Miniato at Florence in Italy, and others, still exist, not having yet been buried by the gradual raising of the ground-level in great towns; also the immense flights of steps in Rome, leading up to the Trinita del Monte and the Capitol, and those found in all towns built on hills, when an architectural composition has guided their plan.
In Egyptian architecture inclined planes took the place of stairs, as in the sloping corridors of the Great Pyramid, the descent leading to the temple of the Sphinx, and the approaches to the two temples of Deir el-Bahri, one of them the oldest temple found. Inclined planes were also provided in front of some of the Greek temples, where the steps of the stylobate were of great height; similar contrivances were adopted by the Mahommedans in Egypt to ascend the minaret of Ibn Tulun and el Hakim; in the great circular tower at Amboise, and in the fallen campanile of St Mark’s, Venice. (R. P. S.)