Curved Staircase & Cable Railing — Harbourside Restaurant, Sydney
Circular Quay, Sydney, Australia — Restaurant and bar, harbourside heritage building with mezzanine basement dining level
Descending into the restaurant, guests experience a sweeping curved staircase — the outer curved stainless stringer catching the harbour-reflected light from the dining space below. Blackbutt timber treads, Australian-grown and locally beloved, ground the metalwork in warmth. The cable railing system — 8 horizontal 316 stainless cables on each side — keeps the harbour view completely unobstructed from the dining mezzanine below. Diners approaching the front door can see through the cable rails directly to the water views below, creating a compelling "what's down there?" effect that is part of the restaurant's brand experience.
Project value: AUD 62,000 – 72,000 (approx. USD 40,000 – 46,000)
The Challenge
Designing a curved staircase into a heritage building in Circular Quay brought several constraints: (1) Sydney Heritage Council required that no new penetrations be made into the original sandstone walls — the staircase needed to be self-supporting without wall anchors. (2) The tight curved geometry (inner radius only 2,400 mm) combined with a 1,400 mm stair width meant the outer stringer needed to be cold-bent from a 10 mm plate to achieve a 3,800 mm outer radius — the tolerances required were tighter than standard shipyard bending work. (3) The cable railing needed to be installed on a curved form — standard through-post threading only works on straight runs. A special curved post-and-fitting system was required. (4) As a restaurant in a heritage building, NCC compliance was reviewed by a private building certifier and a heritage consultant simultaneously.
Our Solution
For the self-supporting requirement, the staircase was designed as a structural frame: the curved stringer at the outer radius was fabricated from 10 mm plate cold-bent in two arcs and welded to a base frame that bolts to the concrete subfloor on both levels. No wall anchors required. The inner radius used a stainless steel tubular spine column (89 mm Ø) that provides torsional resistance. For the cable posts on the curved form, we designed custom curved post-to-handrail brackets that allowed each post to be plumb vertically while accommodating the varying angle of the curved handrail. All cable runs terminate with through-post fittings and turnbuckle tensioners at the top and bottom landing posts. Heritage compliance was achieved by documenting that the installation was entirely reversible — no fixing into sandstone walls.
The Result
The staircase has been described by Sydney restaurant critics as "the most architecturally considered stair in a Sydney restaurant in years." The building certifier and heritage consultant both signed off without requiring modifications to the design. The cable railing allows diners on the upper floor level to maintain full view sightlines to the harbour — as the operators had envisioned. The restaurant cited the staircase as "central to the brand story" in their opening press release.
Technical Deliverables
- Outer Stringer — Curved 10 mm mild steel plate, cold-bent to 3,800 mm outer radius, HD galv + PVD black finish
- Treads — Solid Blackbutt hardwood, 45 mm thick, radius-cut to stair geometry, natural Rubio Monocoat oil
- Cable Rails — 4 mm 1×19 AISI 316 cable, 8 cables per side, 150 mm spacing, turnbuckle tensioners
- Posts — SUS 316 round posts 38 mm Ø, custom curved top bracket, 800 mm centre spacing
- Handrail — SUS 316 brushed 50 mm Ø tube, cold-bent to 3,800 mm outer radius, continuous single piece
- Structural — Self-supporting frame, NCC 2022 Vol 1, AS/NZS 1170.1 calcs, heritage reversibility documentation
- Surface — Outer stringer: PVD titanium nitride black coating; all 316 SS: brushed #4; internal steel: HD galv
- Logistics — Changzhou → Sydney (LCL), 4-week transit; Heritage Council approved material samples shipped ahead of order
"The council wanted everything reversible — and your documentation made that clear from the first submission. The heritage consultant hadn't seen that level of detail from a Chinese supplier before. It made the whole approval process faster than we expected."
Project Scope
- ▸Curved staircase, 2,400 mm inner radius, 1,400 mm width, descent of 3,600 mm floor-to-floor
- ▸Solid Blackbutt timber treads (Australian hardwood, natural oil finish)
- ▸Stainless steel 316 curved plate stringer (outer edge visible as design feature)
- ▸Marine-grade 316 stainless cable railing: 4 mm × 1×19 cables, horizontal, 8 cables per height
- ▸Continuous curved round handrail 50 mm Ø SUS 316 brushed, cold-bent to matching radius
- ▸NCC 2022 + AS/NZS 1170.1 structural documentation for Sydney building certifier