Sunday, May 15, 2016
A stair, or a stairstep is one step in a flight of stairs.[1] 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.[1]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.[1]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, The Battleship
Potemkin).StepThe step is composed of the tread and riser.TreadThe 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 outer edge of the step to the vertical "riser" between
steps. The "width" is measured from one side to the other.RiserThe
vertical portion between each tread on the stair. This may be missing
for an "open" stair effect.NosingAn 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 actually overlap each
other slightly.Starting step or BullnoseWhere stairs are open on one or
both sides, the first step above the lower floor may be wider than the
other steps and rounded. The balusters typically form a semicircle
around the circumference of the rounded portion and the handrail has a
horizontal 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 bullnose can be used when
both sides of the stairs are open.Stringer, Stringer board or sometimes
just StringThe structural member that supports the treads and risers in
standard staircases. There are typically three stringers, one on either
side and one evenly spaced 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.WindersWinders 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.TrimVarious
forms of moldings are used to decorate and in some instances support
stairway elements. Scotia or quarter-round are typically placed beneath
the nosing where a riser and tread to support its overhang.
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