Photograph at night of an office tower in between a carpark tower and another taller office tower; Photograph at night of an office tower in between a carpark tower and another taller office tower;

Capital Square Tower 2, Perth

Sustainable, innovative tower design overcomes complex site challenges

Tower 2, the second of three commercial towers planned for the Capital Square precinct in Perth, covers 30,000sqm of premium grade commercial and retail space over fifteen floors, with flexible workspaces, sweeping views and abundant natural light, via a welcoming double level lobby entrance. 

The workspaces provide collaboration, social connection, focus areas, and a healthy environment for all round wellbeing. The development brings to life a next generation campus style workplace of the future and sparks the much-needed rejuvenation of the west end of the city’s CBD. 

Delivering the new tower was a collaborative effort with our project partners as there were complex structural, civil and geotechnical engineering challenges to overcome, which had hampered the redevelopment of the site for the previous three decades.

Our technical expertise and innovative structural solutions found a way to build a sustainable, repeatable floorplate on a small footprint with existing foundation piles and site constraints. The tower’s design seamlessly integrates with stage 1 of the precinct, Mia Yellagonga, a sustainable, smart and leading-edge campus, which offers access to gym facilities, shops and restaurants along Spring Street. 

Project Summary

~ 30,000sqm commercial development


2,000sqmfloor plates

Photograph looking over an office tower of 15 storeys to the land and bayswater behind Photograph looking over an office tower of 15 storeys to the land and bayswater behind

An innovative, sustainable structural solution with less embodied carbon

The Capital Square site presented challenging conditions, including a gradient, high water table and lack of amenities. The site was previously occupied by a proposed 30 storey hotel building of similar gross area but much smaller footprint and vision for the new design was to utilise the existing foundation piles that had been installed for the previous concept. 

Image ©Osprey Creative

We worked with the team on an efficient structural solution for the building that would deliver flexible, collaborative workspaces and maximise the sweeping views of the Kings Park and Swan River while still working within the constraints of the site.

To reuse the existing piles, the capacity of the superstructure load was limited. A tapered post-tensioned (PT) concrete beam and slab solution was devised to reduce the weight, saving an average of 100mm of slab thickness per floor compared to a PT flat slab solution for the same column grid.

While the main driver was to reduce pile loading, the added benefit was that the 100mm of concrete savings per floor significantly reduced the embodied carbon. 

The outcome was an efficient structural form with 12m cantilevers at the corners, and an 18m back-span acting as a balanced cantilever, challenging the traditional 9x9m commercial grid typically schemed with perimeter columns. This allowed for a lean, sustainable floorplate that was repeatable up the tower, enabling 15 commercial floors of flexible, column free space, maximising views and increasing natural light into the workplaces.

Image ©Osprey Creative

Capital Square Tower 2 is the perfect example of how Arup works collaboratively and creatively to devise innovative solutions to complex, technical challenges. This site is transformed into a thriving business community contributing to the long term social and economic prosperity of Perth. ” David Williams David Williams Project Director

Seamless precinct integration

Capital Square Tower 2’s integration to existing buildings, retail and wellness facilities is a key marker of the success of the project. 

Due to the difference in elevations between the podium and the street level on the opposite elevation, a second entrance to Tower 2 was conceived to allow direct access to the podium structure. The entrance features a wide suspended pedestrian bridge sheltered from the elements by the larger footprint of the tower floor plates of Tower 2. 

With a focus on connectivity and wellbeing, the podium is the social heart of the development providing the community with access to a range of facilities and publicly accessible green spaces.