Stairs are a structure designed to bridge a large vertical distance between lower and higher levels by dividing it into smaller vertical distances. This is achieved as a diagonal series of horizontal platforms called steps which enable passage to the other level by stepping from one to another step in turn. Steps are very typically rectangular, but may instead be straight, curved, or may consist of two or more straight pieces connected at angles. Types of stairs include staircases (also called stairways) and escalators. Some alternatives to stairs are elevators (also called lifts), stairlifts, inclined moving walkways, ladders, and ramps. A stairwell is a vertical shaft or opening that contains a staircase. A flight (of stairs) is an inclined part of a staircase consisting of steps (and their lateral supports if supports are separate from steps).
History This is an excerpt from Staircase. The concept of stairs is believed to be 8000 years old, and is one of the oldest structures in architectural history. The oldest example of spiral stairs dates back to the 400s BC. Medieval architecture saw experimentation with many different shapes, and the Renaissance even more so with varied designs. Due to the simplicity of the design, stairs themselves can't be credited to one culture, and patterns in nature may also be confused, such as basalt columns or other natural formations. The creation of stairs came from the necessity to travel steep passages, and thus, the designs of many steep passages have been found in civilizations in Africa, America, and Asia, though the classifications of some are still subject to review.
Components and terms
A stair, or a stairstep, is one step in a flight of stairs. A staircase or stairway is one or more flights of stairs leading from one floor to another, and includes landings, newel posts, handrails, balustrades, and additional parts. In buildings, stairs is a term applied to a complete flight of steps between two floors. A stair flight is a run of stairs or steps between landings. A stairwell is a compartment extending vertically through a building in which stairs are placed. A stair hall is the stairs, landings, hallways, or other portions of the public hall through which it is necessary to pass when going from the entrance floor to the other floors of a building. Box stairs are stairs built between walls, usually with no support except the wall strings. Stairs may be in a "straight run", leading from one floor to another without a turn or change in direction. Stairs may change direction, commonly by two straight flights connected at a 90° angle landing. Stairs may also return onto themselves with 180° angle landings at each end of straight flights forming a vertical stairway commonly used in multistory and high-rise buildings. Many variations of geometrical stairs may be formed of circular, elliptical and irregular constructions. Ascending a set of stairs to a higher floor is often referred to as going "upstairs", the opposite being "downstairs". The same words can also be used to mean the upper or lower floors of a building, respectively.
Steps
Each step is composed of a tread and a riser. Some treads may include a nosing.
Tread: The part of the stairway that is stepped on. It is constructed to the same specifications (thickness) as any other flooring. The tread "depth" is measured from the back of one tread to the back of the next. The "width" is measured from one side to the other. Riser: The near-vertical element in a set of stairs, forming the space between one step and the next. It is sometimes slightly inclined from the vertical so that its top is closer than its base to the person climbing the stairs. If a physical riser is not present, the design is described as "open riser". This is often the case in unfinished basements. Nosing: An edge part of the tread that protrudes over the riser beneath. If it is present, this means that, measured horizontally, the total "run" length of the stairs is not simply the sum of the tread lengths, as the treads overlap each other. Some building codes require stair nosings in specific cases where the tread depth is below a minimum value. They provide additional length to the tread without changing the pitch of the stairs. Starting or feature tread: Where stairs are open on one or both sides, the first step above the lower floor or landing may be wider than the other steps and rounded. When the starting step is rounded, the balusters typically are arranged in a true spiral around the circumference of the rounded portion, and the handrail has a flat spiral called a "volute" that connects the tops of the balusters. Besides the cosmetic appeal, starting steps allow the balusters to form a wider, more stable base for the end of the handrail. Handrails that simply end at a post at the foot of the stairs can be less sturdy, even with a thick post. A double-ended feature tread can be used when both sides of the stairs are open. There are a number of different styles and uses of feature tread. Stringer board, stringer, or sometimes just string: The structural member that supports the treads and risers in standard staircases. There are typically three stringers, one on either side and one in the center, with more added as necessary for wider spans. Side stringers are sometimes dadoed to receive risers and treads for increased support. Stringers on open-sided stairs are called "cut stringers". Tread rise: The distance from the top of one tread to the top of the next tread. Total rise: The distance the flight of stairs raises vertically between two finished floor levels. Winders: Winders are steps that are narrower on one side than the other. They are used to change the direction of the stairs without landings. A series of winders form a circular or helical stairway. When three steps are used to turn a 90° corner, the middle step is called a kite winder as a kite-shaped quadrilateral. Trim: Various moldings are used to decorate and in some instances support stairway elements. Scotia or quarter-round are typically placed beneath the nosing to support its overhang. Curtail step: A decorative step at the bottom of a staircase that usually houses the volute and volute newel turning for a continuous handrail. The curtail tread will follow the flow of the volute.
Handrails
The balustrade is the system of railings and balusters that prevents people from falling over the edge.
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