Mirvac is planning to extend a prominent high-rise office tower in central Melbourne as tenant demand rises and workers continue to return to the CBD.

The ASX-listed developer plans to refurbish the office building at 90 Collins Street as well as extending it with plans to add 15 levels to the 21-storey tower.

The redevelopment, designed by Fender Katsalidis, aims to strengthen the CBD asset in Collins Street’s sought-after Paris end.

Mirvac general manager of office Andrew Butler said the application complimented the developer’s recent sustainability milestone, hitting net positive carbon nine years ahead of its intended 2030 target.

“Maintaining and refurbishing our existing assets, rather than opting to demolish them, means that we can retain the embodied carbon in the building,” Butler said.

“This fits our ‘whole-life carbon’ portfolio approach, where we consider the carbon emissions produced over the entire lifecycle of a building.”

Mirvac picked up the 21,000sq m tower as part of a $580-million, seven-property deal with GE Real Estate Investments in 2013.

The building, constructed in 1988 and last refurbished in 2011, was occupied by blue-chip tenants Westpac and VicSuper at the time of Mirvac’s acquisition.

It is currently occupied by Banner Asset Management, the British Consulate, Greencape Capital and Greens MP Adam Bandt, among others.

Mirvac’s ambitious plans demonstrate its confidence in the strength of Melbourne’s return-to-the-office.

At the close of the year, Melbourne CBD towers were 12 per cent occupied but 88 per cent leased.

Nevertheless, confidence has increased, backed by hard evidence, and reflected in both increased office investment and raised development ambitions.

The redevelopment will enable Mirvac to provide office accommodation to up to 3500 workers, while also upping the building’s end value to $650 million.

Butler said the additional 15,000sq m of office space planned for the building would be in high demand as companies looking to return to the office considered the needs and wellness of staff.

​​“We believe that high-quality, tech-enabled office spaces with best-in-class sustainability credentials will be in high demand in Melbourne as the city continues to open back up following the impacts of the pandemic,” Butler said.

Fender Katsalidis director Nicky Drobis told The Urban Developer the extension was the result of an exciting yet complex design process.

“This project promotes community engagement and interaction via its ‘third spaces’; a series of highly accessible mixed-use communal meeting and leisure areas,” Drobis said.

“Coupled with the revitalised laneway access, the new precinct will contribute to the lively atmosphere of the entire city block.”

Mirvac’s Collins Street application follows planning approval to refurbish its 380 St Kilda Road office building.

The developer has continued to advance its significant $12.9-billion commercial and mixed-use development pipeline with $2.4 billion now centred in Melbourne.