Helical Stair
By Huu Khanh Nguyen · Updated October 28, 2026 · stair
A stair that turns about an open well, from a quarter turn to two full turns, fitted to the floor height. Step height and largest going Well radius, width and turn Hand Flight construction Straight landing at the top
Parameters
| Name | Default | Unit |
|---|---|---|
| Riser height | 160 | mm |
| Going on the walking line (the tread count is the nearest to it) | 295 | mm |
| Radius of the inner edge of the flight in plan (the well) | 1000 | mm |
| Radial width of the flight | 1500 | mm |
| Turn of the flight in plan, from the first riser to the upper level | 180 | ° |
| Direction of climb seen from above | left | |
| Straight landing at the upper level | true | |
| Landing depth along the direction of travel at the end of the flight | 1219 | mm |
| Landing thickness | 147 | mm |
| Code check of the going readouts below | none | |
| Radius of the walking line (readout) | innerRadius + Math.min(width / 2, 500) | mm |
| Number of risers (readout) | Math.round(angle * (Math.PI / 180) * walklineRadius / going) + 1 | |
| Turn of one step (readout) | angle / (risers - 1) | ° |
| Going on the walking line (readout) | walklineRadius * angle / (risers - 1) * (Math.PI / 180) | mm |
| Going at the inner edge (readout) | innerRadius * angle / (risers - 1) * (Math.PI / 180) | mm |
| Going on the measuring line of the OIB rule (readout) | (innerRadius + 200) * angle / (risers - 1) * (Math.PI / 180) | mm |
| Going on the measuring line of the DB SUA rule (readout) | (innerRadius + 500) * angle / (risers - 1) * (Math.PI / 180) | mm |
| Going at the outer edge (readout) | (innerRadius + width) * angle / (risers - 1) * (Math.PI / 180) | mm |
| Twice the riser plus the going on the walking line (readout) | 2 * rise + walklineRadius * angle / (risers - 1) * (Math.PI / 180) | mm |
| Floor to floor height (readout) | rise * risers | mm |