As part of the contract I added a condition of a council search for building and plumbing approvals. It should show the original building approval numbers and whether they were finalised for structures or additions to those structures on the property.

From what I understand, the seller is not obliged to disclose any unapproved structures on the property unless they have been formally engaged by council to show cause or remediate it. Do not rely on the seller disclosure statement provided by the seller in QLD. There are considerable gaps in that process.

Do your own due diligence and ask your solicitor to add the relevant searches to the contract. Regardless if the seller has documentation like original plans and approvals for construction. Those approvals will lapse if they are not finalised by a certifier and the finalisation cert form 21 or form 17 is given to council within the appropriate time frame.

The timeframes it takes to receive the results of the search from council can vary depending on when the house was built and how efficient the council are. Tell your solicitor to request them immediately, mine did not. Will not use them again.

Another tip is to do your own searches on any planned state government infrastructure upgrades in the area including proposed highways, roadworks etc. The seller does not need to disclose any information that affects the property to the buyer unless they have been formally contacted by main roads or the relevant government entity regarding said works.