Spiral Stair Kit Dimensions and Measurements

If you are ordering a spiral stair kit, you should know the following measurements before you make your purchase.

FLOOR-TO-FLOOR HEIGHT. The floor-to-floor height should be measured from the top of the floor of the lower level to the top of the floor of the upper level. When selecting a stair kit online, review closely the floor-to-floor height ranges and corresponding number of required risers.

DIAMETER. When you visualize your spiral stair from overhead, its footprint at the lower level is a circle and its diameter is the distance across the center. For spiral stair kits, diameters range from very compact 42” up to code-compliant 60" and 63" diameters. To select the best diameter, consider your requirements for the clear width of the tread, well opening, and code compliance.

CLEAR WIDTH. This is the amount of walking area you will have on each step. The clear width for 60” code diameter kits is 26 3/4", and for 63” code diameter kits, it is 28 1/4".

WELL OPENING. This is the opening in your floor at the top of the stair. Spiral stair kits require a well opening greater than the diameter of the stair (for example, a 60” diameter spiral stair kit will go through a well opening minimum of 62” x 62”, if passing through a floor). In addition to installations through a well opening, spiral stair kits can attach to the side of a balcony, deck, loft, or any upper level.

Diameter Tread Width Clear Width of Tread Platform Size Well Opening (Square | Circular)
17 3/4”
22" x 22"
44" x 44" | 44" dia.
20 3/4”
25" x 25"
50" x 50" | 50" dia.
23 3/4”
28" x 28"
56" x 56" | 56" dia.
26 3/4”
31" x 31"
62" x 62" | 62" dia.
29 1/2"
28 1/4”
65" x 65"

Shop our spiral stair kits, or if you need a larger diameter spiral stair or help, contact us or ask a question.