Premier global construction company, Multiplex, has completed Fivex's $24 million Riverview House commercial office building at 276 Flinders Street in Melbourne's CBD.

Designed by architects Baldasso Cortese with engineers Bonacci Group and IrwinConsult, the second tower of Riverview House has an innovative and highly-sustainable design featuring cross laminated timber and lightweight steel.

Located opposite Melbourne's iconic Flinders Street Station, the new building spans five levels delivering 4,000 square metres of lettable office space and is connected to the existing tower lobby via a bridge link at each level.

The bridge link features a highly efficient truss design to alleviate the transfer of new loads onto the existing building. A weatherproof expansion joint has been installed between the bridge and the original building, allowing them to move independently.

"We are delighted to be complete this innovative and highly sustainable office project," said Graham Cottam, Regional Managing Director of Multiplex Victoria.

Construction work commenced on Riverview House in March, 2018 and according to Multiplex during peak construction over 115 people worked on site.

Riverview House was a technically complex project with innovative construction methods including the use of lightweight materials such as a modular structural steel grid and cross-laminated timber floor panels tolimit the need to strengthen the existing structure below and enable compliance with engineering codes.

"The building had many challenges from a design point of view. Balancing a new structure on top of a fully-occupied 3-storey podium floors while achieving code compliance created unique design issues," said Baldasso Cortese Partner Murray Brassington.  "It was great to have Multiplex input through the design stage to resolve these issues in a practical way."

Construction challenges included the active, live operational environment and the sites location on a busy corner in the CBD.

The location of the project, directly above occupied tenancies and adjacent to one of Australia's busiest intersections, brought a unique set of logistical constraints and challenges. Structural steel cantilevered protection decks allowed the new building to be encapsulated by scaffolding, providing overhead public protection and access for feature cladding.

The building is designed to 5 star ESD with features including a new rainwater tank installed in an existing plantroom to allow for rainwater harvesting technology.

276 Flinders Street is Fivex's newly refurbished mixed-use retail precinct. The podium and ground levels comprise a fitness and childcare centre and a range of retail and food stores, with extensive office space above.

Multiplex has completed a number of commercial projects across Melbourne over the past few years including Tower 5 at Collins Square, Cbus Properties Medibank office at 720 Bourke Street, National Australia Bank building at 700 Bourke Street and Queensland Investment Corporations development in Collins Street.