Overview

A custom exterior spiral stair connecting a lower deck to a rooftop terrace, fabricated from rolled plate steel stringers with brake-formed steel treads and risers, and finished with a rolled tube steel railing that sweeps continuously from base to top landing.

 

Scope & Process

The stair was fully 3D modeled in Rhino, with the geometry driven parametrically in Grasshopper to control the helical stringer curvature, tread rotation, and railing sweep. Because every stringer and railing component is a curved, rolled element, each part had to be unrolled from its 3D form into flat, developable patterns to produce accurate cut files for laser cutting — a process scripted in Grasshopper to keep the unrolled geometry coordinated with the 3D model as the design evolved.

 

From the coordinated model, complete 2D layout and fabrication drawings were generated for the shop, along with preliminary structural analysis to size stringer plate thickness and confirm the railing tube profiles were adequate for the span and loading.

 

Deliverables

• Parametric 3D model (Rhino + Grasshopper)

• Unrolled/flattened cut files for laser-cut stringers and railing components

• 2D fabrication and layout drawings

• Preliminary structural sizing calculations