Young Brunette Mulatto Girl Reveals A Pink Camisole And Knickers On The Spiral Staircase

Spiral stairs wind around a newel (also the central pole). They typically have a handrail on the outer side only, and on the inner side just the central pole. A squared spiral stair assumes a square stairwell and expands the steps and railing to a square, resulting in unequal steps (larger where they extend into a corner of the square). A pure spiral assumes a circular stairwell and the steps and handrail are equal and positioned screw-symmetrically. A tight spiral stair with a central pole is very space efficient in the use of floor area. Spiral stairs have the disadvantage of being very steep. Unless the central column is very large, the circumference of the circle at the walk line will be small enough that it will be impossible to maintain a normal tread depth and a normal rise height without compromising headroom before reaching the upper floor. To maintain headroom most spiral stairs have very high rises and a very short going. Most building codes limit the use of spiral stairs to small areas or secondary usage.
The term "spiral" is used incorrectly for a staircase from a mathematical viewpoint, as a mathematical spiral lies in a single plane and moves towards or away from a central point. A spiral staircase by the mathematical definition therefore would be of little use as it would afford no change in elevation. The correct mathematical term for motion where the locus remains at a fixed distance from a fixed line whilst moving in a circular motion about it is "helical". The presence or otherwise of a central pole does not affect the terminology applied to the design of the structure.
Spiral stairs in medieval times were generally made of stone and typically wound in a clockwise direction (from the ascender's point of view), to place attacking swordsmen (who were most often right-handed) at a disadvantage. This asymmetry forces the right-handed swordsman to engage the central pike and degrade his mobility compared with the defender who is facing down the stairs. Extant 14th to 17th century examples of these stairways can be seen at Muchalls Castle, Crathes Castle and Myres Castle in Scotland. Exceptions to the rule exist, however, as may be seen in the accompanying image of the Scala of the Palazzo Contarini del Bovolo, which winds up counter-clockwise.
Developments in manufacturing and design have led to the introduction of kit form spiral stairs. Steps and handrails can be bolted together to form a complete unit. These stairs can be made out of steel, timber, concrete or a combination of materials.