Architecture, Projects

The Castle Residences


The landmark Castle Residences, located on Sydney’s Bathurst and Castlereagh Streets, is soon to stand tall as a $380 million high-end apartment complex with luxury five-star hotel service and amenities.

Hutchinson Builders began construction of the 37-storey tower began in August 2018, and is set to complete construction by early 2021.

The development, designed by award-winning architects Candalepas Associates, includes the refurbishment of the 142 year old heritage listed Porter House building next door.

Austral Precast project provided an effective solution to space restrictions challenges on site with Double Wall, a unique product which consists of a pair of precast reinforced concrete shells connected by a lattice girder (trusses) fabricated from reinforcement bar, forming a cavity.

Double Wall was used in the basement of the 37 storey high-rise building while solid walls and precast columns are being used extensively on the remainder of the project.

Castle Residences will be home to 131 stunning apartments, and include a 6 level basement. The western façade is crafted from concrete domes on the lower floors. Beyond level 11 the building will cantilever 12m off the side and continue upwards for the next 27 storeys above, giving the allusion of a weightless suspension above the Porter House building.

The western façade is constructed from Austral Precast Solid Wall concrete panels with a Canvas oxide colour, giving a stunning warm tan tone to the building. Atop of the tower sits 5 levels of lush terraced hanging gardens for the residents to enjoy.

This project features Austral Precast Double Wall and Solid Wall.
By Candalepas Associates
Castle Residences

A key feature of the façade design was that the vertical sides to some of the Solid Wall Precast panels were exposed, with complex shapes on the inside. This made production difficult, as traditionally the table face is on the outside of the building, which can be viewed from the street.

Through several workshops with the Architect, Engineer and the Builder, a decision was made to turn the panel around so the table face was inside the building, and the hand finish face was on the outside. This solved the production issues and added a more variable, earthy finish on the façade, which gives the building its character.

The heritage listed Porter House, built in 1867, will feature 121 luxury hotel rooms with four levels of facilities for both residents and hotel guests to experience, including a restaurant, art gallery, private dining facilities and a business centre.

During the refurbishment, the major consideration for developers was to ensure the character of the building was preserved, as the 1876 Victorian Classic-style building has significant presence on the Castlereagh streetscape.

Constructing a new 37-level tower without disturbing the heritage listed building on the same land proved to be extremely limiting for builders when surveying the best building methodology. With the basement walls needing to withstand extremely heavy loads, they are often constructed by conventional methods with reinforcement, formwork and concrete all placed by hand, on site.

“With all the benefits of off-site factory production, the client gained a greater amount of space on the construction site.”

Graeme Tunbridge
Austral Precast Sales Coordinator

“With all the benefits of off-site factory production, the client gained a greater amount of space on the construction site.”

Graeme Tunbridge
Austral Precast Sales Coordinator

Limited space around the perimeter of the building, particularly when building on the boundary of the heritage-listed building, meant that conventional formwork was not viable for this project.

Unsure of the best way to combat this issue, Hutchinson Builders contacted Austral Precast for a solution, which was to install an Austral Precast Double Wall system.

‘Protecting and preserving the heritage-listed Porter House building was of utmost importance throughout this build, which made Double Wall the ideal solution for the builders,’ says Austral Precast Sales Coordinator Graeme Tunbridge. ‘With all the benefits of off-site factory production, the client gained a greater amount of space on the construction site which was essential for ensuring minimal disturbance to the Porter House, as well as greater speed in construction.’

Austral Double Wall is a prefabricated precast concrete panel system that enables greater savings in installation costs and time, and is an excellent solution for any load-bearing wall including basements, shafts, core walls and other functional walls.


As its name suggests, the Double Wall system is characterised by a pair of precast reinforced concrete shells that are connected by a lattice girder, forming a cavity. Steel reinforcement, edge forms and built-in components may be factory assembled and transported to the construction site as part of the system, which was the case for the Castle Residences project.

According to Graeme Tunbridge, the Double Wall also provided a safer working environment for the builders on site. ‘When using Double Wall there is minimal excavation required, far less materials needed and less personnel on-site, which provides a far safer construction method than traditional blocklaying or cast-in-situ technique,’ he says. ‘The builders also achieved installation efficiency through the reduced crane load capacity, the enhanced jointing method and the lack of welding and formwork required for the basement’.

Another important consideration for the construction of this project was ensuring the structure was just as functional in its longevity, as it is in its installation. The Double Wall system is commonly used for high-rise buildings due to its high resistance to wind, earthquake and soil loads. The structure also has excellent fire resistance performance, achieving a Fire Resistance Period for structural adequacy, integrity and insulation in accordance with the National Construction Code- Building Code of Australia, Specification 3. Type A Fire Resisting Construction.

Double Wall also has high thermal mass, minimising the impact of external temperature changes to internal living areas which contributes passively to achieve the comfort zone.

The Double Wall will store heat energy for an extended period, gradually releasing it over time. In winter, high thermal mass buildings will remain relatively warm, while in summer they will remain relatively cool.

Featured Products
Precast Concrete
Austral Precast Double Wall
  • Characterised by its reduced weight, Double Wall enables greater savings in installation costs and time while adding monolithic design advantages to the many other construction advantages the Austral Precast whole of structure offer brings.
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Precast Concrete
Austral Precast Solid Wall
  • Solid Wall are cast in factory and delivered on site, ready for installation. Suitable for use as a façade, functional wall or an ideal solution for structural load bearing applications, Solid Wall offers limitless creativity combined with a magnitude of functional construction advantages.
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