Aidan Ellis and every other apartment owner in the Landmark building at Charlestown will pay the anticipated $400,000 bill to rectify defective work in his apartment, and the cost of his rent.

Mr Ellis and wife Jocelyn moved out of their penthouse apartment on Thursday as a second penthouse owner continues to live in rented accommodation nearly nine months after the start of more than $300,000 in repairs to her apartment.

"We've tried to get through to this government, to the various ministers, to the other political parties, that what is happening at the moment is crazy," said Mr Ellis, who has campaigned for more than five years for significant law changes to hold developers and private certifiers more accountable when apartment buildings have problems.

He has also campaigned for changes to legislation about the operation of strata committees after lengthy disputes over rectification work at the Landmark building.

"No one wants to spend money fixing work in someone else's apartment because the work wasn't done the way it should have been in the first place," said Mr Ellis.

"I don't want to spend the money, but the apartment was unliveable. Water poured in when it rained, there's no insulation and things got worse the longer nothing was done.

"The problem is this is happening all over the state and governments aren't doing anywhere near enough to address the issue. The rugged bit is the developers responsible for these kind of builds are nowhere to be seen when things go wrong, and there's nothing you can do about it once their companies go under."

Mr Ellis said the Sydney Opal apartment building saga that left 300 residents on the street on Christmas Eve because of defects, only months after the building's completion, highlighted major problems in NSW apartment building regulations and law, including the use of private certifiers by builders and developers.

But his campaign for legislative change had put him in contact with many others across the state experiencing major physical, financial and emotional stress because of shoddy building work after a NSW unit-building boom.

Mr Ellis said many people were struggling to pay the special levies imposed on apartment owners when rectification work was required on common property areas because of building defects, where developers and builders could not be held accountable.

"When things go wrong the owners' corporation must maintain the common property and that means special levies for each individual apartment owner, whether they can afford it or not," Mr Ellis said.

NSW Government reforms in 2018 include a strata building bond and inspections scheme requiring developers to lodge a bond that can be drawn on to repair defects "early in the building lifecycle".

The government also increased penalties and enacted a code of conduct for certifiers.