New figures suggest the repair bill for structural and safety defects in apartment buildings across Australia could top $6.2 billion.

That figure is considered conservative, as it only covers remediation of water leaks, fire safety breaches, structural failure and combustible cladding in units built since 2009.

It does not include potential legal costs, audit schemes or increased insurance premiums, or any buildings older than 10 years.

The CFMMEU commissioned the research and says the cost assessment is staggering.

“Tens of thousands of families, many of whom have purchased their first home, are now stuck with the crippling cost and mental anguish of owning homes that they may not be able to live in, are unsafe and cannot afford to repair,” the CFMMEU's Dave Noonan said in a statement.

New South Wales was predicted to be the most expensive state to remediate, followed by Victoria and Queensland, with flammable cladding the biggest expense.

“Our analysis highlights that the cost to Australia will be substantial,” the Equity Economics report said.