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Calculate spiral stair dimensions, step counts, and design parameters instantly. Determine the number of steps, rise height, tread angles, and handrail length for your spiral staircase design.
Typical value: 7.5"
Common: 270°, 360°, 450°
Enter values above to calculate spiral stair dimensions.
Steps = Angle / 360 × Height / 7"
Assumes ~7" ideal rise per step
Tread Angle = Total Angle / Steps
Handrail = √(Arc² + Height²)
Arc = Circumference × Rotations
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A spiral staircase is a compact vertical circulation solution where steps rotate around a central column. Unlike traditional straight stairs, spiral stairs follow a helical path, making them ideal for tight spaces and creating dramatic architectural statements.
Spiral stairs are commonly used in towers, lofts, small apartments, and as secondary circulation in multi-story buildings. They offer both functional and aesthetic benefits, providing efficient space usage while creating visual interest.
Key Feature: Spiral stairs require the least floor area of any stair type, typically occupying only the space needed for the diameter of the rotation.
The vertical distance between steps should be comfortable, typically between 7 and 8 inches. This promotes safe and comfortable climbing for users of varying abilities.
The running surface depth at the walkline (typically 18" from center) should be at least 10 inches for safety and comfort. Measure tread depth along the walkline, not at the inner or outer edge.
Maintain minimum 6'8" (80") of headroom above each step. For spiral stairs, check clearance above the center column as users progress around the spiral.
Handrails must be 34-38" high and provide a continuous graspable surface. Guards should prevent users from falling through openings greater than 4 inches.
Typical residential spiral stairs range from 4-6 feet in diameter. Larger diameters (6-8 ft) provide more comfortable treads and are suitable for commercial applications.
Spiral stairs are not ADA compliant for primary means of egress. They may be used for secondary circulation in certain applications, but must meet strict dimensional requirements and include handrails on both sides.
Building codes vary by location. Always check with your local building department before finalizing spiral stair designs. Residential versus commercial requirements may differ significantly.
The vertical distance from one step to the next. For comfort and safety, target 7-7.75 inches. Consistent rise throughout the staircase is critical.
The angle each step rotates around the centerline. Calculated as total rotation angle divided by number of steps. Typical values are 10-20° per step.
The actual length of handrail needed, accounting for both the spiral path and vertical rise. Longer spirals and greater heights increase handrail length significantly.
The distance from the center column where the main circulation occurs, typically 18 inches from the column center. Tread measurements are taken along this line.
Spiral stairs naturally have narrower treads near the center and wider treads at the outer edge. The calculator shows both dimensions to understand tread geometry.
Total degrees the spiral rotates. Common values: 270° (3/4 turn), 360° (full turn), 450° (1.25 turns). Affects step count and overall height per step.
Durable, modern appearance. Can be finished with powder coat or paint. Requires maintenance to prevent rust. Excellent for contemporary designs.
Warm aesthetic, traditional appeal. Choose durable species like oak, cherry, or walnut. Requires regular maintenance and sanding/refinishing over time.
Steel structure with wood treads offers durability and aesthetic appeal. Steel provides structural support while wood provides warmth and elegance.
Glass treads with stainless steel frames create an open, modern look. Requires careful maintenance for cleanliness and safety considerations.
Calculate steps by dividing your total height by your desired step rise (typically 7 to 7.75 inches). The calculator automatically handles this using a standard 7-inch rise assumption, then adjusts based on your specific height and rotation angle.
Stair diameter is the full width of the spiral from outer edge to outer edge. The walkline radius is where people actually walk, typically 18 inches from the center column. This is where tread depth is measured according to building codes.
Building codes generally don't allow spiral stairs as the only means of exit in occupancies that require two exits. However, they can be secondary circulation in most building types. Always verify local codes for your specific application.
For residential stairs, a 4-6 inch diameter column is typical. For commercial applications, 6-8 inches or larger may be needed depending on structural requirements. The column must support the stair weight and occupant loads.
This is one of the biggest challenges with spiral stairs. Precision manufacturing is essential. Professional spiral stair manufacturers use specialized equipment to ensure each step height is identical, within 1/8 inch tolerance.
Custom spiral staircases typically cost $3,000 to $10,000 or more per step, depending on materials, diameter, height, and finishes. A 12-step residential staircase could range from $36,000 to $120,000. Use the cost calculator for budget estimation based on your specifications.
Minimum 80 inches (6'8") of clear headroom is required above the tread at any point on the spiral. In some applications, you may need more. Check that headroom is maintained throughout the entire spiral rotation, especially above the center column.
Spiral stairs can be challenging for very young children, elderly individuals, and people with mobility impairments. The rotating geometry and potentially steep rise can be difficult. Ensure sturdy handrails on both sides and consider alternative circulation options when accessibility is a priority.
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