page_title: Stairs
section_title: Spiral and helical stairs
hierarchical_section_title: Stairs / Forms / Spiral and helical stairs
caption_attribution_description: English: Staircase in Vatican Museum. Français&#160;: Escalier du Musée du Vatican. Vatican Museums &#160;&#160;Native nameMusei VaticaniLocationVatican CityCoordinates41°&#160;54′&#160;23″&#160;N, 12°&#160;27′&#160;16″&#160;E &#160;Established1506Web pagewww.museivaticani.vaAuthority control : Q182955 VIAF:&#8201;141443926 ISNI:&#8201;0000 0001 0807 3165 LCCN:&#8201;n81003002 GND:&#8201;235092-0 SUDOC:&#8201;032013795 WorldCat institution QS:P195,Q182955 Photo was taken using the following technique: Film: Fuji Velvia Lens:	2.0/20 Filter: none Body: Minolta 9000 Support: balustrade Source: http://fam-tille.de/sparetime.html Image with Information in English Bild mit Informationen auf Deutsch
context_page_description: A stairway, staircase, stairwell, flight of stairs, or simply stairs, is a construction designed to bridge a large vertical distance by dividing it into smaller vertical distances, called steps. Stairs may be straight, round, or may consist of two or more straight pieces connected at angles.
  Special types of stairs include escalators and ladders. Some alternatives to stairs are elevators, stairlifts and inclined moving walkways.
context_section_description: Spiral stairs, sometimes referred to in architectural descriptions as vice, wind around a newel (also the central pole). In Scottish architecture, they are commonly known as a turnpike stair. 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 if they are tight or are otherwise not supported by a centre column, for two reasons:
  The wider the spiral, the more steps can be accommodated per spiral. Therefore, if the spiral is large in diameter, via having a central support column that is strong (invariably large in diameter) and a special handrail that helps to distribute the load, each step may be longer and therefore the rise between each step may be smaller (equal to that of regular steps). Otherwise, the circumference of the circle at the walk line will be so small 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, some spiral stairs have very high rises to support a very short diameter. These are typically cases where the stairwell must be a small diameter by design or must not have any center support by design or may not have any perimeter support.
  An example of perimeter support is the Vatican stairwell shown in the next section or the gothic stairwell shown to the left. That stairwell is only tight because of its design in which the diameter must be small. Many spirals, however, have sufficient width for normal size treads (8 inches) by being supported by any combination of a center pole, perimeter supports attaching to or beneath the treads, and a helical handrail.  In this manner, the treads may be wide enough to accommodate low rises. In self-supporting stairs the spiral needs to be steep to allow the weight to distribute safely down the spiral in the most vertical manner possible. Spiral steps with centre columns or perimeter support do not have this limitation. Building codes may limit the use of spiral stairs to small areas or secondary usage if their treads are not sufficiently wide or have risers above nine and a half inches.
  The term "spiral" has a more narrow definition in a mathematical context, as a mathematical spiral lies in a single plane and moves towards or away from a central point. The 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.
  When used in Roman architecture spiral stairs were generally restricted to elite structures. They were then adopted into Christian ecclesiastic architecture. There is a common misconception that spiral staircases in castles rose in a clockwise direction to hinder right-handed attackers. While clockwise spiral staircases are more common in castles than anti-clockwise, they were even more common in medieval structures without a military role such as religious buildings. Studies of spiral stairs in castle have concluded that "the role and position of spirals in castles ... had a much stronger domestic and status role than a military function" and that "there are sufficient examples of anticlockwise stairs in Britain and France in [the 11th and 12th centuries] to indicate that the choice must have depended both on physical convenience and architectural practicalities and there was no military ideology that demanded clockwise staircases in the cause of fighting efficiency or advantage".
  Developments in manufacturing and design have led to the introduction of kit 
caption: The 'Bramante' staircase, Vatican museums, showing the two access points at the bottom of the stairs
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