Plate stairs
The fabricated spiral staircase: plate treads round a centre column, and the sums for the whole stair -- the riser, the turn, the going on the walkline, the headroom and the handrail.
Spiral Staircase
Spiral staircase calculator: riser, turn, going on the walkline, headroom and handrail length, with the plate tread as DXF and 1:1 template. Free.
Which stair to use
- Spiral staircase round a centre column, with plate treads: Spiral Staircase.
How it is calculated
The riser is the floor-to-floor height divided by the number of risers, one more than the treads, because the upper floor is the last step. Each tread turns its angle round the column, and the headroom is one turn of risers less the plate.
The tread is an annular sector, from the column radius to the stair radius, opened to the tread angle plus the overlap at the outer edge. The result gives the PDF template at 1:1 and the DXF for plasma or laser.
Frequently asked questions
- How many treads per turn on a spiral staircase?
- Twelve, at 30°, is the most common: they give about 190 mm (7.5 in) of going on the walkline of a 1.60 m (63 in) stair. With sixteen, at 22.5°, the going drops to 142 mm, under the 171 mm (6¾ in) IBC 2021 asks for.