Dunedin's historic courthouse was opened briefly yesterday as Ministry of Justice officials walked media through the mothballed building.
Hard hats and high-visibility vests were mandatory for the tour, which took in the High Court, jury court, law library and more - areas deemed at high risk of damage in a moderate earthquake.
The ministry's general manager commercial and property, Fraser Gibbs, and deputy secretary corporate Suzanne Stew, flew from Wellington yesterday to lead the tour.
Mr Gibbs said the courthouse's stone tower and the 40-tonne stone ''pepper pots'' adorning its outside perimeter were obvious features needing strengthening work.
The courthouse was really made up of three different buildings, and how they moved together in an earthquake was a key focus for engineers, he said.
Also of particular note was the building's historic interior, which in general could not be altered during strengthening work because of its category-one heritage listing.
That made any needed work far more complicated, he said, which had contributed to projected costs.
Mr Gibbs said a business case being developed by the ministry would be ready in draft form next month, and would show the expected cost and details of required work.
The 2013 announcement from then courts minister Chester Burrows that strengthening work was imminent was made before ''detailed designs'' were completed, he said.
Dunedin courthouse
What we know
• Required strengthening work will cost ''north'' of $10million.
• Strengthening work will not include ''base isolation'' being installed in the building's foundations, which were described as ''OK'' yesterday.
• It is expected two ''diaphragms'' of heavy plywood will encircle the complex at ground and first-floor level.
• The business case is due to be completed next month.
• Required strengthening work, if approved, could take between two and three years.
What we don't know
• How far ''north'' of $10 million required work will be.
• Whether there is a monetary limit the ministry will not cross.
• What is causing the expected bill to be so high.
• Why the ministry won't commit to returning court services to the building.
• The details of five of six engineering reports completed for the ministry. The ministry says only the initial 2011 Opus report is fit for public view.
