Some 560 families impacted by the collapse of builder Porter Davis will be able to get their deposits back.

It applies to customers who paid deposits before the builder went into liquidation last month but were left without insurance coverage.

Premier Daniel Andrews said he believed the scheme would cost about $15 million, averaging about $25,000 per customer.

About 1,700 homes across Victoria and Queensland were left in limbo when Porter Davis went into liquidation last month.

Some 560 families impacted by the collapse of builder Porter Davis will be able to get their deposits back 

The Victorian Building Authority is investigating whether Porter Davis has breached any laws after customers claimed they were left without domestic building insurance despite paying their deposits.

On Wednesday it was revealed the company collapsed owing close to $33 million to the Commonwealth Bank, on top of other debts.

Liquidators Grant Thornton are still trying to determine Porter Davis' overall financial position.

'Our investigations are ongoing to determine if these debts are cross collateralised across the group,' Grant Thornton said in a statement. 

The liquidators are still trying to determine Porter Davis' overall financial position.

As a secured creditor, CBA would be first in line to get its money back. It's believed millions are also owed to unsecured creditors.

The documents state main entity PDH Group has a total estimated debt of $28.8 million, and had a cash deficit of about $533,000 in the bank at the time of its demise.

Among the secured creditors named is Chesapeake Holdings Pty Ltd, which owns Chesapeake Thoroughbreds - run by Porter Davis founder Anthony Roberts. 

Premier Daniel Andrews said he believed the scheme would cost about $15 million, averaging about $25,000 per customer

The documents also reveal a Deloitte advisor to Porter Davis first contacted Grant Thornton about liquidating the company on March 23, a week before it was publicly revealed it had gone bust. Grant Thornton was appointed on March 31. 

When Porter Davis collapsed in March it was Australia's 12th biggest home builder.

The company left 1,500 homes in Victoria unfinished and another 200 in Queensland half-built.

The company also had collected deposits from another 779 clients whose money was left uninsured. 

Nostra Property Group (NPG) announced on Monday that it will buy Porter Davis Homes' multiple dwelling business.

NPG have several big-name clients including Villawood Properties, Stockland, Lendlease and Frasers Property.

Grant Thornton said it will work to see the deal through quickly. 

'This will see a number of jobs preserved, disruption minimised for several existing and future projects, and critically up to 375 homes built for families who have had to suffer enormous stress and anxiety following the collapse of the PDH Group,' financial advisor Said Jahani said.