Spiral Staircase Calculator
Design a spiral staircase with accurate dimensions. Calculate riser height, tread width, stringer length, and check IRC compliance for your stair project.
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Spiral Staircase Dimensions
Frequently Asked Questions
What is the minimum diameter for a spiral staircase?
IRC requires minimum 60 inches diameter (5 ft) for a spiral staircase to allow 26 inch clear tread width at the walk line.
What is the maximum riser height for a spiral staircase?
IRC allows maximum 9.5 inch riser height for spiral staircases, compared to 7.75 inches for standard stairs.
How many treads do I need for a 10 ft ceiling?
A 10 ft ceiling (120 inches) with 9 inch risers needs about 14 treads. Always round up and check headroom clearance.
Do spiral staircases need a landing?
Spiral staircases are considered one continuous flight and do not require intermediate landings. They must meet minimum tread depth requirements.
Can a spiral staircase be a primary egress?
Yes, spiral staircases can serve as a required egress if they meet IRC minimums: 60" diameter, 9.5" max riser, 26" walk line tread, and 6'6" headroom.