Sydney Opal Tower gardens central to cracking investigation

Engineers have turned to the spectacular communal gardens of Sydney’s trouble-hit Opal Tower to find the source of the cracks that have led residents to be evacuated twice in four days.

• Some Opal Tower residents refuse to leave
• ‘Ripple effect from tower defect is enormous’

A major selling point of Sydney’s trouble-hit Opal Tower may turn out to be its downfall as engineers turn to its spectacular communal gardens to find the source of the cracks that have led residents to be evacuated twice in four days.

The Saturday Telegraph can reveal they are investigating the 16 prefabricated concrete panels used in the garden slots, which architects Bates Smart called a way to “invite some of the parkland into the building”.

In a presentation made three months ago to an audience of architects, Bates Smart studio director Mathieu Le Sueur explained how they used the precast concrete in the design of the much-trumpeted “communal gardens in the sky”.

Various cranes and constructions sites around Sydney being developed. Cranes at Sydney Olympic Park with the Opal Tower in the foreground. Picture: Toby Zerna

Professor Mark Hoffman, one of two independent experts yesterday appointed by the state government to investigate the fiasco, described the design of the 36-storey building as “unique”.

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He said the concrete cracking which began on Christmas Eve next to the garden on level 10 was a “pretty rare occurrence”.

“There’s clearly some very notable damage there but the issue we’re all grappling with is the cause of it, we have to inspect a lot of other parts of the building as well,” Prof Hoffman, the Dean of Engineering at the University of NSW, said.

“The first place you’d look at is the design of the structure because it’s unique, it’s a little bit different.”

Residents pack up and leave Opal Tower. Picture: Jordan Shields

They have been told it could be at least 10 days before they are allowed back. Picture: Jordan Shields

A team from Evolution Precast Systems, which made the concrete panels, was yesterday on site working with builders Icon, developer Ecove, design engineering firm WSP, Prof Hoffman and fellow expert Professor John Carter.

After being allowed to return on Christmas Day, around 300 residents have been evacuated for a second time. Many were seen yesterday carting boxes, bags and teddy bears out after being told they would have to exit the building for at least 10 days.

Some have refused to leave.

Premier Gladys Berejiklian was said to be “furious” people had to leave their homes over Christmas and New Year.

“She expects the full weight of the law to be applied if anyone is found to have done the wrong thing,” a spokesman said. “Safety can never be compromised.”

Structural engineer Charles Rickard said there was “obviously” a structural issue at the tower block which had worsened as the week went on.

Professors Hoffman and Carter moved to reassure the public that the use of precast concrete was common.

“(It) is a building method used throughout Australia and many countries across the world,” they said.

The 16 concrete panels adjacent to the internal community gardens are a major part but only one part of inquiries, sources said.

Ecove director Bassam Aflak said residents had been offered a range of options for accommodation and financial support. He said the builder would bear the cost of the repair bill.