Three-Level Spiral Staircase Feature — Tech Campus, Singapore

The Challenge

The project presented three main challenges: (1) Height: a 9.1 m floor-to-floor height across three levels is exceptional for a spiral staircase — standard fabrication tooling accommodates up to 6 m. The central column needed to be fabricated in two field-splice sections with a precision-engineered flanged connection at mid-height. (2) Tread finish coordination: the terrazzo finish was to be poured after steel installation — this required the steel tread pans to be perfectly level with a 20 mm rebate depth for the terrazzo layer. Pan geometry and level precision during installation were critical. (3) Singapore structural code requires Execution Class EXC3 for public stairways, requiring a higher welding standard and NDT testing.

Our Solution

The central column was manufactured in two sections with a precision-machined flanged splice at 4,550 mm height. A field-splice drawing was provided showing the bolt pattern, alignment mark, and torque specification. The two sections were connected on-site in less than two hours. Tread pans were laser-cut to ±0.5 mm accuracy with a 20 mm perimeter rebate for the terrazzo contractor. A level-checking procedure (using a digital level) was included in the installation guide. For EXC3 compliance, all welds were tested by magnetic particle inspection (MPI) and visual inspection — MPI test reports were included in the compliance package. The structural calculations were submitted to Singapore's BCA (Building and Construction Authority) for structural plan check.

The Result

The staircase was operational within 3 weeks of on-site installation start, with terrazzo treads completed in the following week. The BCA structural plan check was approved without revision — the first time the project team had cleared plan check on a custom staircase without a revision request. The feature staircase has been included in the building's marketing materials and is the centrepiece of the company's APAC brand identity.

Technical Deliverables

• Central Column — SUS 316, 168 mm Ø, 9,100 mm total, 2-section with precision flanged splice at 4,550 mm
• Tread Count — 44 treads across 3 floors (220 mm rise × 44 = 9,680 mm; each floor landing acts as tread 0)
• Tread Pans — Mild steel 3 mm plate, 20 mm rebate perimeter for terrazzo, laser-cut, galvanized
• Glass Panels — 12 mm clear toughened, EN 12150, custom cut for varying spiral geometry (no two panels identical)
• Handrail — Continuous cold-bent SUS 316 brushed 50 mm Ø tube, 3-floor continuous helix (no joints)
• Structural — SS EN 1993 calcs, EXC3, MPI weld inspection reports, BCA plan check submission package
• Surface Finish — 316 SS brushed #4 throughout; carbon steel elements hot-dip galvanized + epoxy primer
• Logistics — Changzhou → Singapore (40 ft HC container), 3-week transit, port-to-site delivery