Spiral Stair
By Huu Khanh Nguyen · Updated October 29, 2026 · stair, unit
Wedge steps that wind around a central column up to a top platform. Floor height and step height Stair diameter and column size Turn per step and hand Top platform or none Code check of the steps Finish
Parameters
| Name | Default | Unit |
|---|---|---|
| Total rise (floor to floor) | 2800 | mm |
| Maximum riser height (the number of risers is the fewest that keeps every riser under it) | 190 | mm |
| Outer radius (stair diameter / 2) | 762 | mm |
| Column tube outside diameter | 88.9 | mm |
| Turn angle of one step | 32 | ° |
| Step and platform thickness | 40 | mm |
| Hand (right climbs counterclockwise seen from above, left clockwise) | right | |
| Top platform | true | |
| Code check of the readouts below | none | |
| Finish | white | |
| Number of risers (readout) | Math.ceil(sizeZ / riser) | |
| Riser height (readout) | sizeZ / risers | mm |
| Clear walk between the column and a handrail on the outer edge (readout) | outerRadius - (columnDiameter / 2) - 31.75 | mm |
| Tread depth at the measuring radius (readout) | angle * Math.PI / 180 * (code == 'ncc' ? (columnDiameter / 2) + 0.7 * (outerRadius - (columnDiameter / 2) - 31.75) : ((columnDiameter / 2) + 305)) | mm |
| Clear height above a tread, one turn up (readout) | 360 / angle * rise - thickness | mm |