Abstract: A stairset for the fabrication of a spiral stairway on-site, and a method for the assembly of the stairset. This stairset includes a central support to receive spacers to position a plurality of stair tread units at a selected separation (riser height), the stair treads extending horizontally outward. Further, components for a banister (handrail) are a plurality of segments, being a selected number for each stair tread unit, that are threaded upon a cable. The cable is provided on at least one end with means for tensioning, with final tensioning after general assembly of components (post-tensioning). A plurality of balusters are attached to, and extend downwardly from, at least a portion of segments of the resultant banister to be fastened to distal ends of the stair tread units. Specifically, the same number of balusters join the selected number of banister segments for each stair tread.