Paragon spiral stairs offers several base models that are adjustable height spiral stairs as indicated in the heights (will fit). This is helpful when final finished floor-to-floor height has yet to be set and or if the final floor-to-floor measurements are still undetermined.
Adjustable Height means that you can set the riser heights when you receive the stair. Therefore, if you originally calculate your floor-to-floor height to be 100 inches and then later re-calculate and learn that the actual height in two inches bigger, do not worry because Paragon stairs have adjustable risers.
The correct number of treads on your spiral stair are predetermined based on the anticipated height of your project. In order to determine how many treads your stair will have take your finished floor to floor height and divide it by the maximum rise height of 9.5.
Keep in mind the straight stair riser height and spiral stair risers height is different. Most straight stairs have a typical riser height between 7” – 7.5” whereas spiral stair riser height has a maximum riser height of 9.5”. The reason for this is that as all the treads are set to a near 30 degree angle.
Example: if your finished floor-to-floor height is 12 feet, that translates to 144 inches. 144 inches / the maximum spiral stair riser height of 9.5 inches = 15 treads