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Spiral vs Helical Staircase: Structure, Space and Fabrication
People often use "spiral" and "helical" for the same thing, but on drawings they usually mean two different structures, and the difference changes the footprint, the fabrication and the cost. We fabricate feature staircases in our own Dongguan factory and have done so for over 20 years. Here is how we explain the difference to designers.
Spiral staircase: a centre column
A spiral staircase winds around a central column. Each tread is fixed to the column, and often to a handrail or outer stringer as well. Because the column takes most of the load, the stair can be compact, and the structure is easy to understand. The trade-off is that the column sits right in the middle of the view, and the inner end of each tread is very narrow.
Helical staircase: helicoidal stringers and an open well
A helical staircase has no centre column. Inner and outer stringers curve in plan and rise at the same time, so each stringer is a doubly curved, helicoidal member. The treads span between them and the centre stays open. It looks lighter and the walking line is more generous, but the stringers have to be formed accurately in three dimensions.
Space and the slab opening
The choice usually starts with the space. A spiral stair fits a smaller floor area and a smaller slab opening. A helical stair needs a larger footprint and a larger opening to keep a comfortable tread width and enough headroom as it turns. The floor-to-floor height sets the number of risers, and the angle of turn sets how the stair lands on the upper floor. These are worth agreeing before the slab is cast.
How each is fabricated
A spiral stair is mostly straight work: a tube or column, treads and a handrail. A helical stair takes far more forming. Stringers are made either by plate rolling, for plate-steel stringers and side plates, or by section bending (curving) and twisting, for I-section stringers. In our factory, every helical stair goes through full shop pre-assembly, so curves, riser heights and section joints are checked before anything leaves.
Delivery
After pre-assembly the stair is match-marked and dismantled into sections sized for transport and access to the building. Each section receives its surface treatment and is delivered to site.
Helical staircases we have fabricated
- Shenzhen Marriott Hotel Nanshan: hotel lobby helical staircase
- Multi-level helical staircase, Hangzhou
- Haitian office building, Foshan: plate-steel helical staircase
- Twisted-plate staircase and twisted I-section staircase: workshop fabrication
More in projects and on the profile bending page.
Next step
Common questions about drawings and delivery are answered in our helical staircase FAQ. If you already have a plan and floor heights, send them and we will tell you which form suits the space.
Not sure which form fits your space?Email a plan and floor-to-floor heights. We reply in English.