NSW's newly-appointed building commissioner has told a parliamentary inquiry into the state's building industry he's embarrassed sub-standard apartments were sold in the now-cracked Mascot Towers.
Inaugural building commissioner David Chandler appeared before the upper house's public accountability committee on Friday after starting in the role on Wednesday.
Mr Chandler visited Mascot Towers on Thursday before telling the inquiry - which is examining building standards, quality and disputes - that he believes the engineering design was "poor".
Residents of the complex's 132 apartments were forced to stay elsewhere after the building was evacuated in mid-June due to cracking in the primary support structure and facade.
"I've built a lot of buildings and ... I don't think I've seen many buildings as poorly built as that," Mr Chandler said.
"I'm quite certain that the builder didn't know how to read any construction plans because the faults that are in that building ... simply someone who didn't pay any attention to them.
"I'm embarrassed, frankly, that the industry has allowed a product like Mascot Towers to turn up on the marketplace."
The state's building industry needs to "rebuild its reputation", Mr Chandler said.
"Our industry is overly self-facing and it has an unsustainable culture of risk-aversity and 'What's in it for me?' This culture has too often become defensive and adverse to accountability."
Electrical Trades Union NSW branch secretary Justin Page said there were 30,000 licenced electrical contractors in the state but in the past 12 months only 8000 lodged the safety and compliance certification required by the Department of Fair Trading for each installation.
In the past fortnight, the union found 28 advertisements seeking electricians who were unlicenced or qualified overseas, or for trade assistants to do electrical work. That's in breach of state legislation.
Some of the advertised jobs were for major state government projects including NorthConnex and Westconnex, Mr Page said.
Plumbing Trades Employees Union NSW assistant secretary Chris Seet called for all fire protection and plumbing work to be carried out by licenced professionals.
While plumbing, drainage and gas fitting requires a licence in the state, mechanical services work does not, he said.
"This work is highly specialised and technical. Failure of these systems can lead to things like Legionella outbreak, major flooding and flammable explosions."
Likewise, Mr Seet said, a licence isn't required to work on medical gas systems servicing hospital wards and surgical theatres.
At Bankstown-Lidcombe Hospital in 2016, nitrous oxide was confused for oxygen, leaving one newborn baby dead and another with permanent brain damage,
"That's the result of unqualified people coming in and doing complicated plumbing work," Mr Seet said.
Mr Chandler told the inquiry that NSW doesn't need a formal building commission like some other states.
"On the face of it, I don't believe we need that at the moment, the first thing we need is to be very clear about what leadership we need to start turning this industry around," he said.
Legislation was passed in October giving the NSW government compliance and enforcement powers, and the right to suspend or cancel a building certifier's registration, but the new regime is yet to come in effect.
The upper house inquiry was established following the Mascot and Opal Tower incidents.
The newly-built Opal Tower block in Sydney Olympic Park was evacuated on Christmas Eve after cracks discovered in the building sparked fears it could collapse.