Stair Bridge - geograph.org.uk - 578932.jpg

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. Stairs may be straight, round, or may consist of two or more straight pieces connected at angles.

Types of stairs include staircases (also called stairways), ladders, and escalators. Some alternatives to stairs are elevators (also called lifts), stairlifts, inclined moving walkways, 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).

Components and terms

A ''stair'', or a ''stairstep'', is one step in a flight of stairs.R.E. Putnam and G.E. Carlson, ''Architectural and Building Trades Dictionary, Third Edition'', American Technical Publishers, Inc., 1974, 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 ''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. 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 degree angle landing. Stairs may also return onto themselves with 180 degree angle landings at each end of straight flights forming a vertical stairway commonly used in multistory and highrise buildings. Many variations of geometrical stairs may be formed of circular, elliptical and irregular constructions.

Stairs may be a required component of egress from structures and buildings. Stairs are also provided for convenience to access floors, roofs, levels and walking surfaces not accessible by other means. Stairs may also be a fanciful physical construct such as the "stairs that go nowhere" located at the Winchester Mystery House. Stairs are also a subject used in art to represent real or imaginary places built around impossible objects using geometric distortion, as in the work of artist M. C. Escher.

"Stairway" is also a common metaphor for achievement or loss of a position in the society; or as a metaphor of hierarchy (e.g. Jacob's Ladder, Battleship Potemkin).

Step

Each step is composed of a tread and a riser. Some include 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.
* 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. Many building codes require stair nosings for commercial, industrial, or municipal stairs. 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 form a spiral around the circumference of the rounded portion, and the handrail has a spiral called a "volute" that supports the top 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 centre, 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 spiral 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 the staircase which usually houses the volute and volute newel turning for a continuous handrail. The curtail tread will follow the flow of the volute.

The railing system

The balustrade is the system of railings and balusters that prevents people from falling over the edge.
* Banister, railing, or handrail: The angled member for handholding, as distinguished from the vertical balusters which hold it up for stairs that are open on one side. Railings are often present on both sides of stairs, but can sometimes be only on one side or absent altogether. On wide staircases, there can be one or more railings in between the two sides. The term "banister" is sometimes used to mean just the handrail, sometimes the handrail and the balusters, or sometimes just the balusters.
* Volute: A handrail end element for the bullnose step that curves inward like a spiral. A volute is said to be right or left-handed depending on which side of the stairs the handrail is as one faces up the stairs.
* Turnout: Instead of a complete spiral volute, a turnout deviates from the normal handrail centre line away from the flight to give a wider opening as one enters the staircase, The turnout is usually set over a newel post to give added stability to the handrail.
* Gooseneck: The vertical handrail that joins a sloped handrail to a higher handrail on the balcony or landing is a gooseneck.
* Rosette: Where the handrail ends in the wall and a half-newel is not used, it may be trimmed by a rosette.
* Easings: Wall handrails are mounted directly onto the wall with ''wall brackets''. At the bottom of the stairs such railings flare to a horizontal railing and this horizontal portion is called a "starting easing". At the top of the stairs, the horizontal portion of the railing is called an "over easing".
* Core rail: Wood handrails often have a metal core to provide extra strength and stiffness, especially when the rail has to curve against the grain of the wood. The archaic term for the metal core is "core rail".
* Baluster: A term for the vertical posts that hold up the handrail. Sometimes simply called ''guards'' or ''spindles''. Treads often require two balusters. The second baluster is closer to the riser and is taller than the first. The extra height in the second baluster is typically in the middle between decorative elements on the baluster. That way the bottom decorative elements are aligned with the tread and the top elements are aligned with the railing angle.
* Newel: A large baluster or post used to anchor the handrail. Since it is a structural element, it extends below the floor and subfloor to the bottom of the floor joists and is bolted right to the floor joist. A ''half-newel'' may be used where a railing ends in the wall. Visually, it looks like half the newel is embedded in the wall. For open landings, a newel may extend below the landing for a decorative ''newel drop''.
* Finial: A decorative cap to the top of a newel post, particularly at the end of the balustrade.
*Baserail, or shoerail: For systems where the baluster does not start at the treads, they go to a baserail. This allows for identical balusters, avoiding the second baluster problem.
* Fillet: A decorative filler piece on the floor between balusters on a balcony railing.

Handrails may be ''continuous'' (sometimes called ''over-the-post'') or ''post-to-post'' (or more accurately ''newel-to-newel''). For continuous handrails on long balconies, there may be multiple newels and ''tandem caps'' to cover the newels. At corners, there are ''quarter-turn caps''. For post-to-post systems, the newels project above the handrails.

Another, more classical, form of handrailing which is still in use is the tangent method. A variant of the Cylindric method of layout, it allows for continuous climbing and twisting rails and easings. It was defined from principles set down by architect Peter Nicholson in the 18th century.

The earliest spiral staircases appear in Temple A in the Greek colony Selinunte, Sicily, to both sides of the cella. The temple was constructed around 480–470 BC.

Other terms

;Apron: This is a wooden fascia board used to cover up trimmers and joists exposed by stairwell openings. The apron may be moulded or plain, and is intended to give the staircase a cleaner look by cloaking the side view.
* Balcony: For stairs with an open concept upper floor or landing, the upper floor is functionally a balcony. For a straight flight of stairs, the balcony may be long enough to require multiple newels to support the length of railing.
* Flight: Any uninterrupted series of steps between floors or levels.
* Floating stairs: A flight of stairs is said to be "floating" if there is nothing underneath. The risers are typically missing as well to emphasize the open effect, and create a functional feature suspended in midair. There may be only one stringer or the stringers otherwise minimized. Where building codes allow, there may not even be handrails.
* Landing, or platform: A landing is the area of a floor near the top or bottom step of a stair. An intermediate landing is a small platform that is built as part of stairs between main floor levels and is typically used to allow the stairs to change directions, or to allow the user a rest. A half landing, or half-pace, is where a 180° change in direction is made, and a quarter landing is where a 90° change in direction is made (on an intermediate landing). As intermediate landings consume floor space, they can be expensive to build. However, changing the direction of the stairs allows stairs to fit where they would not otherwise, or provides privacy to the upper level as visitors downstairs cannot simply look up the stairs to the upper level due to the change in direction. The word 'landing' is also commonly used for a general corridor in any of the floors above the ground floor of a building, even if that corridor is located well away from a staircase.
* Mobile safety steps: Can be used as temporary, safe replacements for many types of stairs
* Runner: Carpeting that runs down the middle of the stairs. Runners may be directly stapled or nailed to the stairs, or may be secured by a specialized bar, known as a stair rod, that holds the carpet in place where the tread meets the riser.
* Spandrel: If there is not another flight of stairs immediately underneath, the triangular space underneath the stairs is called a "spandrel". It is frequently used as a closet.
* Staircase: This term is often reserved for the stairs themselves: the steps, railings and landings; though often it is used interchangeably with "stairs" and "stairway". In the UK, however, the term "staircase" denotes what in the U.S. is called "stairway", but usually includes the casing – the walls, bannisters and underside of the stairs or roof above.
* Stairway: This primarily American term is often reserved for the entire stairwell and staircase in combination; though often it is used interchangeably with "stairs" and "staircase".
* Stairwell: The spatial opening, usually a vertical shaft, containing an indoor stairway; by extension it is often used as including the stairs it contains.
* Staircase tower: A tower attached to, or incorporated into, a building that contains stairs linking the various floors.

Measurements

The measurements of a stair, in particular the rise height and going of the steps, should remain the same along the stairs.

The following stair measurements are important:
* The ''rise height'' or ''rise'' of each step is measured from the top of one tread to the next. It is not the physical height of the riser; the latter excludes the thickness of the tread. A person using the stairs would move this distance vertically for each step taken.
* The ''tread depth'' of a step is measured from the edge of the nosing to the vertical riser; if the steps have no nosing, it is the same as the going; otherwise it is the going plus the extent of one nosing.
* The ''going'' of a step is measured from the edge of the nosing to the edge of nosing in plan view. A person using the stairs would move this distance forward with each step they take.
* To avoid confusion, the ''number of steps'' in a set of stairs is always the number of risers, not the number of treads.
* The ''total run'' or ''total going'' of the stairs is the horizontal distance from the first riser to the last riser. It is often not simply the sum of the individual tread lengths due to the nosing overlapping between treads. If there are ''N'' steps, the total run equals ''N''-1 times the going: the tread of the first step is part of a landing.
* The ''total rise'' of the stairs is the height between floors (or landings) that the flight of stairs is spanning. If there are ''N'' steps, the total rise equals ''N'' times the rise of each step.

* The ''slope'' or ''pitch'' of the stairs is the ratio between the rise and the going (not the tread depth, due to the nosing). It is sometimes called the ''rake'' of the stairs. The ''pitch line'' is the imaginary line along the tip of the nosing of the treads. In the UK, stair pitch is the angle the pitch line makes with the horizontal, measured in degrees. The value of the slope, as a ratio, is then the tangent of the pitch angle.
* ''Headroom'' is the height above the nosing of a tread to the ceiling above it.
* ''Walkline'' – for curved stairs, the inner radius of the curve may result in very narrow treads. The "walkline" is the imaginary line some distance away from the inner edge on which people are expected to walk. Building code will specify the distance. Building codes will then specify the minimum tread size at the walkline.

Forms

Stairs can take a large number of forms, combining winders and landings.

The simplest form is the straight flight of stairs, with neither winders nor landings. These types of stairs were commonly used in traditional homes as they are relatively easy to build and only need to be connected at the top and bottom; however, many modern properties may not choose straight flights of stairs because:
* the upstairs is directly visible from the bottom of a straight flight of stairs.
* it is potentially more dangerous in that a fall is not interrupted until the bottom of the stairs.
* a straight flight requires enough space for the entire run of the stairs.

Another form of straight staircase is the space saver staircase, also known as paddle stairs or alternating tread staircases, that can be used for a steeper rise, but these can only be used in certain circumstances and must comply with regulations.

However, a basic straight flight of stairs is easier to design and construct than one with landings or winders. Although the rhythm of stepping is not interrupted in a straight run, which may offset the increased fall risk by helping to prevent a misstep in the first place, many stairs will require landings or winders to comply with safety standards in the Building Regulations.

Straight stairs can have a mid-landing incorporated, but it is probably more common to see stairs that use a landing or winder to produce a bend in the stairs as a straight flight with a mid-landing will require a lot of linear space and is more commonly found in commercial buildings. "L" shaped stairways have one landing and usually change in direction by 90 degrees. "U" shaped stairs may employ a single wider landing for a change in direction of 180 degrees, or two landings for two changes in direction of 90 degrees each. A Z-shaped staircase incorporates two parallel 90° turns, creating a shape similar to that of the letter ‘Z’ if seen from above. Use of landings and a possible change of direction have the following effects:
* The upstairs is not directly visible from the bottom of the stairs, which can provide more privacy for the upper floor.
* A fall can be halted at the landing point, reducing the distance someone would fall to reduce risks.
* Though the landings consume total floor space, there is no requirement for a large single dimension, allowing more flexible floorplan designs.
* For larger stairs, particularly in exterior applications, a landing can provide a place to rest the legs.

Other forms include stairs with winders that curve or bend at an acute angle, three flight stairs that join at a landing to form a T-shape, and stairs with balconies and complex designs can be produced to suit individual properties.

A mono string staircase is a term used for a steel spine staircase with treads.

A double string staircase has two steel beams on either side and treads in the center.

Spiral and helical stairs

Spiral stairs (спирално степениште).jpg, Spiral stairs in Art Deco style. Nebotičnik skyscraper, Ljubljana
YangonSecretariatStaircase.jpg, Double spiral staircase of the Ministers' Building (The Secretariat) in Yangon
Scala Contarini del Bovolo (Venice).jpg, The external spiral staircase of Palazzo Contarini del Bovolo, Italy
ŽigmundovaVeža.jpg, upGothic spiral staircase clockwise in St. Elisabeth Cathedral in Košice ( Slovakia)
Industrial spiral staircase.png, Industrial spiral staircase
VaticanMuseumStaircase.jpg, The 'Bramante' staircase, Vatican museums, showing the two access points at the bottom of the stairs

Spiral