Design, construction flaws at Opal Tower

Residents of Sydney's Opal Tower were evacuated on Christmas Eve after cracks were spotted.
Residents of Sydney's Opal Tower were evacuated on Christmas Eve after cracks were spotted.

Critical support beams in Sydney's Opal Tower were left susceptible to "bursting" because they were under-designed and some made from lower strength concrete, an independent report has found.

The newly-built block in Sydney Olympic Park was evacuated on Christmas Eve after cracks were found in the building, sparking fears it could collapse.

A NSW government-commissioned report, released publicly on Friday, found that while the building was structurally sound overall, there were several structural and construction issues responsible for the damage.

Horizontal support beams in the building were of inferior strength and were not compliant, while the decision to only partially grout between the beams and panels added to the problem.

"We found some of the as-constructed hob beams and panel assemblies were under-designed according to the National Construction Code and Australian Standards," professors Mark Hoffman, John Carter and Stephen Foster said.

"This left the hob beams susceptible to failure by shear compression and bursting."

Testing also showed lower-strength concrete was used in some hobs on level four, which "likely precipitated the observed major damage".

However, the tower's builders Icon, said a report by an independent concrete technologist confirmed the hob beam's strength was in "excess" of the design requirement.

Icon also said in a statement that it is conducting remediation works in seven areas of the building and expects completion in four to six weeks after consent is given by the building's body corporate.

NSW Minister for Better Regulation Matt Kean said Icon and the building's developers Ecove would be liable for the defects.

"We'd encourage people to get independent legal advice," he told reporters.

Planning Minister Anthony Roberts described the Opal Tower debacle as "a most harrowing and nerve-racking situation".

"Residents will work through remaining safety concerns with the builder," Mr Roberts said.

The engineers' report recommended creating databases of registered engineers and NSW building certifications, along with a building structure review board to monitor known property design flaws and shape future building codes.

Mr Kean said the government had already committed to creating a database of registered engineers.

Ecove said it supports any initiative to return the community's confidence in the building and construction industry.

"We have always enjoyed a strong reputation for delivering high quality developments and this has been nothing short of devastating to us," director Bassam Aflak said in a statement on Friday.

"If the industry and community can benefit from a more robust process of quality control as a result of this incident, then it has not been for nothing."

About 150 of the building's 392 units remain empty, with the report recommending a host of repair work take place before occupants move back in.

Australian Associated Press