Wendeltreppe aus Holz in Basel

Filigree appearance for steel spiral staircases

Steel spiral staircases with all-glass railings

The sophisticated steel spiral staircases in the new Roche office tower form a perfect ensemble of steel and glass.

Project description

Exclusive steel spiral staircases for office tower

At its headquarters in Basel, the pharmaceutical company F. Hoffmann-La Roche AG is building its new office tower, which is currently the tallest building in Switzerland. As a twin tower next to the existing Building 1, the slim Building 2 with its 205-metre height provides space for about 3,500 employees and is expected to open in mid 2022. The design by the architects Herzog & de Meuron was developed together with the general planning company Drees & Sommer in a terraced construction method as a sustainable and energy-efficient building that accommodates also a café, a bistro as well as several outdoor terraces. As a central eye-catcher, the steel spiral staircases and all-glass railings characterise the stylish interior design of the office tower. Only sustainable building materials and processing methods were used for all constructions.

Elegant steel spiral staircases in various types

There are a total of 16 steel spiral staircases with glass balustrades extending over 45 storeys and, in combination with the curved all-glass gallery railings, they represent an imposing ensemble of steel and glass. Despite the immense amount of steel used, the complex shows a dynamic and light character. Due to their very sophisticated technical design the transitions to the ceiling balustrades are almost graceful. The highly detailed stair constructions differ in their storey height, running width, number of risers and stair layout. The all-glass railings running along both sides and the structurally supporting soffit cladding of the steel spiral staircases result in a homogeneous appearance of the overall structure.

Glasgeländer Wendeltreppe Basel
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Project details

Steel spiral staircases featuring soffit lining

  • Double-sided structurally supporting box-type steel stringers to accommodate the glass railings
  • Welded-in folded tread step construction with recessed steps
  • Inner and outer stringer curved in different radii, ascending course, varying stringer height, stringer width approx. 140 mm
  • Structurally supporting, smooth steel soffit cladding, exactly flush welded steel sheets between the stringers with spatial curvature according to the curvature of the floor plan and the varying heights of the lower edges of the stair stringers
  • Installation of ducts for on-site sprinkler system in the soffit of the steel spiral staircase

Filigree all-glass railings for steel spiral staircases

  • Parapet-high glass railings on both sides made of extra white float glass, 3×6 mm
  • Ascending course, curved in different radii, glass joints max. 10 mm
  • Glass panes with Sentry Foil to realise the extremely narrow curved radii of curvature at the transitions between the stairs and ceiling balustrades while meeting all static requirements
  • Execution of a glass breakage test using a pendulum impact test

Transparent glass railings for the galleries

  • Curved glass panes made of extra white float glass, glass joints max. 10 mm
  • Running horizontally and at parapet height at the ceiling openings
  • Inserted into the steel ceiling frames as top-side recess construction with U-shaped clamping profile

Curved wooden handrail in excellent design

  • Customised handrail profile: rounded on 4 sides with different radii, milled on all sides on 5 axes plus groove to attach to glass railings
  • On both sides of the steel spiral staircases and at the gallery railings
  • Solid wood European Oak, multi-layer glued, oiled surface, custom-made in cooperation with our partner company Holz-Hacker
  • Glued directly onto the glass railings
  • Handrail ending running downwards along the free vertical glass edge

Complex installation of the steel spiral staircases and glass railings

  • “Just in time” supply and assembly of the prefabricated stair elements by means of a construction crane due to lack of storage or installation facilities in the city area.
  • Installation period of the steel spiral staircases over 3 years with advanced logistics and the highest technical precision
  • Latest installation technology for the all-glass railings with a specially developed method

Architectural office:
Herzog & de Meuron Basel Ltd.

General planning:
Drees & Sommer Schweiz AG

Beat Ernst, © Roche Ltd.

Insights staircase assembly Building 2

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