Extending Building Height and Life with Mass Timber: 55 Southbank Boulevard, Melbourne

Session: Track F: Best Tall Building Award By Function: Residential/Hotel, Part 2 & Renovation Award

Scott DaviesJulian AndersonProject image

Scott Davies
Managing Director, Hume Partners

Julian Anderson
Director, Bates Smart

The first cross-laminated timber (CLT) extension project in Australia, 55 Southbank Boulevard uses approximately 1,730 metric tons of CLT to add 10 levels to an existing six-story steel and concrete commercial building, sequestering nearly 2,800 metric tons of carbon dioxide from the atmosphere and introducing a mix of uses to the evolving Southbank neighborhood. Since the original building opened in 1989, Southbank’s urban fabric has changed dramatically, as it became the city’s densest and tallest inner-city neighborhood.

The renovation added 10 hospitality levels, which translates to 220 hotel rooms. The original building was designed to support an additional six steel and concrete floors. However, CLT is approximately 20 percent of the weight of concrete, essentially doubling the number of levels that could be built above the existing structure. CLT components prefabricated off-site resulted in increased construction efficiencies and decreased impact on surrounding buildings. The resulting building achieves additional height and introduces a new use—a serviced hotel. It also models how CLT design and construction can be applied to existing buildings to efficiently adapt to current needs, all while minimizing environmental impact.

The lightweight nature and simplicity of the structural system enabled the project to work with the existing lifts, back of house, and services, reducing demolition of the existing structure. A small crew of three electric luffing crane operators and five carpenters assembled the elements on-site using only screw guns, and could install one floor every two days. This resulted in almost no waste of structural elements during construction, drastically reduced construction noise and build time, and enabled the commercial building below to remain operational throughout construction.

View Building Information on CTBUH.org