A "crisis of confidence" has developed in the NSW building industry, the Insurance Council of Australia has said, as residents and owners of the Mascot Towers building in Sydney's south face another day of lockouts.

Key points: The Insurance Council of Australia said there were concerns about risk controls in the building industry

The Insurance Council of Australia said there were concerns about risk controls in the building industry Engineers still do not know the root cause of the building cracks

Engineers still do not know the root cause of the building cracks Tenants were not aware of legal action underway about a separate building defect before the cracks appeared, a spokesman for the minister said

Six days after the 10-storey high rise was evacuated, it remains partly off limits due to the cracks that appeared in the building's beams on Friday night.

Distressed tenants of the apartment block are being told to go to the Salvation Army if they are facing financial hardship.

The ABC understands at least one couple that own an apartment in Mascot Towers will have to declare bankruptcy if, as expected, costs associated with the cracks run into the millions.

"There is a crisis of confidence developing," Karl Sullivan from the Insurance Council of Australia said.

"The insurance industry is continuing to express its concern. Certainly for some time now, we've had concerns over all the risk controls that are available in the building industry and how some of those are executed."

That is a sentiment echoed by Federal Industry Minister Karen Andrews, who is calling for consistent certification standards.

"We need to look at consistent processes for determining who is going to be qualified to certify those buildings," she said.

"It's patchy, it's not good enough and it doesn't lead to any confidence whatsoever in the building sector."

Less than six months ago, 3,000 residents of the Opal Tower in Sydney Olympic Park had a snap evacuation after fears arose the whole building would collapse.

A report on the incident found parts of the tower were constructed using "lower-strength concrete" and "under-designed" critical support beams had burst under extreme pressure.

Engineers still have not found the cause of the cracks in the Mascot Towers building. ( AAP: Bianca De Marchi )

Tenants unaware of prior litigation

The ABC has been told engineers still do not know what the root cause of the problem at Mascot Towers is — but possibilities include groundwater and excavation work being done on the block next door.

Engineers are continuing to monitor the apartment block and will report back to residents and owners on Thursday night, a spokesman for Minister for Better Regulation Kevin Anderson said.

Litigation by the building's owners' corporation about a building defect identified before Friday night's evacuation had been ongoing for some time, the Minister's spokesman confirmed.

But the Minister said he was very concerned that tenants had no information about that legal action.

For resident Fabiano Dos Santos, there is very little sign of help forthcoming — but he was allowed back home briefly on Tuesday after four days of being without even a wallet.

"I got a couple of minutes — just a couple of minutes to grab my stuff — to get my medicine, my wallet so we can go shopping. So at least things were made a little bit better now," he said.

"It is very frustrating to see the politicians on TV saying they're giving all the support they can and all the residents are being supported — that's not happening."

Tenants are entitled to a waiver or reduction in rent until they can occupy the building under Department of Fair Trading regulations.

If the real estate agent or property owner refuse the request, tenants should notify Fair Trading, and an officer would help them negotiate, the Minister's spokesman said.

Premier Gladys Berejiklian said the Government hoped legislation overhauling the building industry would be introduced in the next session of Parliament.