The present invention relates to a prefabricated spiral staircase in which the heights between treads can be freely and finely adjusted, thus being conveniently assembled and installed at installation sites having different story heights.

Described herein are systems and methods of manufacturing a spiral staircase assembly for custom projects. A method may include coupling a plurality of stairs to a center column such that distances between adjacent stairs of the plurality of stairs deviates less than ½″ to meet code. A method may further include cutting the center column after coupling the plurality of stairs to the center column to form a first center column and a second center column. A method may further include welding a female column coupling to a first end of the first center column and welding a male column coupling to a first end of the second center column. The male column coupling is configured to couple to the female column coupling such that when the male column coupling is coupled to the female column coupling, distances between adjacent stairs of the plurality of stairs deviates less than ½″.