Upgrade of the existing building to a high quality A-Grade commercial office

Situated on a prominent corner location directly adjacent to North Sydney railway station, 73 Miller Street has been transformed into a high-quality A-Grade office building with ground-floor retail and 13 levels of office accommodation.

The refurbishment of the 30-year-old existing building includes the extension of the floor areas from Level 1 to 11 and 2 levels to the existing structure.

Various construction types were explored in the early stage of the project to maximise the leasable area on each level while keeping the weight of extension within the existing structure capacity. A mixture of post-tensioned concrete banded slab and composite steel structure was used in the final design scheme.

The layout and load path of the existing structure challenged the design team, where the floor layout and load-bearing elements change from level to level. Different structural designs had to be adopted to produce a viable solution to meet the client's requirements.

Advanced finite element modelling of reinforced concrete floor and wall systems was widely used on this project to reproduce the behaviour of the existing structure, to verify the current and modified capacity when subjected to the additional loads.

The TTW Façade team developed a new high-performance façade in association with architects Fitzpatrick + Partners and main contractors Buildcorp to provide floor to floor glazing and enhance the views of Sydney Harbour.

Our team of expert engineers started with heavy demolition, which included removing the existing zig-zag façade's aluminium windows and upturn beams around the perimeter. Then, they moved to the eventual infilling of the balconies to extend the floor plates, resulted in a net gain of 4,654m2 of space.

The design challenge for our TTW Façade team was to work around the existing structure and geometry of the building. However, they opted to unitised curtain wall facades with integrated features such as curved corners and projected wing facades, while the glass in the external façade was selected to maximise visible light transmittance while keeping high thermal insulation performance.

Client: ESR

Architect: Fitzpatrick + Partners

Project Manager: Colliers International

Builder: Buildcorp

Value: $58M

Completion: 2020

Sector: Commercial/Industrial

Services: Structural, Civil, Facade