A scaffolding company has been fined $2 million over a "catastrophic" collapse at a Sydney construction site, which killed a young apprentice.

Christopher Cassaniti was working at a building site at Macquarie Park in April 2019 when overloaded perimeter facade scaffolding gave way.

The 18-year-old was directly underneath when it collapsed and was trapped by rubble and debris for 20 minutes before he died.

His colleague, Khaled Wehbe, was also trapped and suffered crush injuries.

Synergy Scaffolding Services pleaded guilty to one offence under the Work Health and Safety Act.

NSW District Court Judge Andrew Scotting today found workers were put in "significant peril" and the collapse was the consequence of a "culmination of events", including the unauthorised removal of building ties.

"This case should serve as a telling reminder that unsafe acts on a building site can and do lead to catastrophic consequences," he said. 

"Workers contemplating such unsafe acts should pause to consider what they might say to the people whose lives are torn apart by the possible consequences of their actions."

He fined the company $2 million, after a 10 per cent reduction for the guilty plea.

The maximum penalty for the offence is $3 million.

The court heard the scaffolding was found to have a load of nearly 18-tonnes, in excess of its maximum capacity.

Judge Scotting found the company knew there had been a history of the unauthorised removal of building ties and alteration to the scaffolding.

He said it was also constructed without vertical bracing, in breach of its own design and the Australian Standard.

Between early March 2019 and the day of the collapse, the company also knew the scaffolding was "grossly overloaded", the judge said.

"The overloading of the scaffold, the lack of vertical bracing, the removal of the ties and the removal of the transoms made the likelihood of the risk occurring so high that it was almost certain," he said.

Video of the scene shortly after the collapse showed one worker yelling at police to "f***ing do something".

Mr Cassaniti's family has previously described him as a gentle, kind, hardworking young man who was adored by everyone who met him.

Today, Judge Scotting acknowledged his relatives continue to suffer immense heartache, grief and loss.

He said the teenager, who had celebrated his 18th birthday just days before his death, was keen and eager to learn and a young man who any employer would be proud to have.

The judge also noted Mr Wehbe continued to be affected by "the horror of that moment".

Synergy Scaffolding Services was engaged to design, erect and maintain the scaffolding by principal contractor GN Residential Construction, which was fined $900,000 in 2020.

At the time, Judge Scotting said steps to eliminate or minimise that risk — which had been identified in the agreement with Synergy in its safety documentation — were "simple and inexpensive".

Mr Cassaniti's mother, Patrizia Cassaniti, said the outcome was in line with their expectations given the maximum available penalty in NSW.

But she said the judge could only impose a fine based on the law and called for higher maximums, in line with what other states and territories have implemented with industrial manslaughter laws.

"It's not a deterrent for any company," Ms Cassaniti said in Melbourne.

"Two million dollars for a big builder is nothing, it's laughable."

Ms Cassaniti said the family was enduring a life sentence and the outcome of the court case didn't change their loss.

"For us, going on every single day it's like waking up and dealing with it every single day.

"When Christopher got his job, we were so proud of him, and then to turn 18.

"He was so excited to have just hit his new milestone. To only live for days into that life milestone is just heartbreaking, because of somebody's complacent decision."