hairpin stairway
A stairway whose flights reverse direction by 180 degrees between floors, without a third direction of ascending steps.
A hairpin stairway consists of multiple flights which turn 180 degrees relative to each other between floor levels. This is one of the most common stairway arrangements because of its relative simplicity and because it uses space more economically than other common configurations. Hairpin stairs take up about half the space of alternating stairs; they occupy approximately the same total space as simple stairs, except that they do not require the hallway space necessary to connect at each floor to the next flight.
The landing of a hairpin staircase is usually just wide enough to give access to both flights and the wall between them, with enough depth to make a comfortable turn. However, the landing may also be wide enough to produce a large gap between the two flights. If there are any stairs on the landing adding a third direction of stairs, then the stairway should be classified as u-shaped.
A broad landing can leave a large gap between the flights without changing the hairpin form. Steps ascending across that connecting area introduce the third direction required by the U-shaped configuration.
