interlaced helix stairway
Two or more helical stairways interwoven around the same axis within one shaft or vertical space.
An interlaced helical stairway is a set of helical stairways (usually only two) interlaced with each other in the same shaft or vertical space. This form of stairway is sometimes used to accommodate bi-directional travel within a narrow space, such as a tower or steeple with an observation deck on top. In such cases it is common for one of the stairways to be designated for climbing and the other for descending.
Each route remains a helix while sharing the vertical space with the others. Two routes are usual, but the definition allows more.
Assigning one route upward and another downward is a possible circulation arrangement. Opposing one-way use is not mandatory for the interlaced geometry.
Related definitions
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alternating stairway
Straight stair flights that reverse direction at each floor level, allowing continuation without a long connecting walk. -
angled stairway
A generally L-shaped stairway with one turn of about 90 degrees between successive floors, using a landing or winders. -
angular helix stairway
A stairway following an angular polygonal path around a central core, shaft, open space, or atrium. -
curved stairway
A stairway following a curved path without completing a circle or helix, including stacked half-circular flights. -
fan stairway
A spreading stairway with angles or bends in individual steps, producing a fan-like or amphitheater-like arrangement. -
hairpin stairway
A stairway whose flights reverse direction by 180 degrees between floors, without a third direction of ascending steps. -
helix stairway
A stairway arranged around a central axis in a circular path, with or without a central post or open shaft. -
interlaced alternating stairway
Two alternating stairways interwoven within one stairwell, with adjacent straight flights rising in opposite directions. -
interlaced angular helix stairway
Two or more angular helical stairways interwoven within the same shaft or vertical space. -
meandering stairway
Stairs which turn at or between levels but do not fold back in the same stairwell. -
progressive stairway
Multiple stair flights continuing along one straight route through successive levels without requiring a turn. -
simple stairway
One or more straight stair flights, with successive flights vertically aligned and reached by walking back at each floor. -
split stairway
Stairs whose pathway forks into clearly distinct directions on the way up or down. -
u-shaped stairway
A stairway with ascending flights in three directions and two turns between floors, forming a rectangular half-helix.