staircase

A stairwell or stair room is a room in a building where a stair is located, and is used to connect walkways between floors so that one can move in height. Collectively, a set of stairs and a stairwell is referred to as a staircase or stairway. In buildings with several housing units, a stairway can be a necessary common area for getting to and from apartments.
Staircases provide vertical access to connected floors in a multi-story building, and are a functional part of it. Stairwells are often used to place several stairs one above the other to save vertical space. The entrance to elevators is often located in the stairwell. Sometimes the stairwell goes around the lift shaft, other times it is placed next to it.
An exterior stairway is a stair in a separate structure attached to the rest of the building body, and can either be enclosed or exposed to the elements. Such temporary exposed stairways are sometimes used in conjunction with scaffolding on construction sites, or permanently as an emergency exit.

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