In estimated $18 million to $20 million will be required to finish the Rotorua Museum renovation, a council report reveals.

It follows Local Democracy Reporting revealing a confidential April 14 Rotorua Lakes Council report which said the 106-year-old museum – which has been closed since 2016 due to seismic concerns following the Kaikoura earthquake – would need an estimated minimum $15m more to finish.

The building's renovation has funding to date of $53.5m, including $15.5m from the council. Last month, the council confirmed $6.3m had been spent.

The confidential report revealed the council considered accepting a lower, 70 per cent New Building Standard for the museum, in order to avoid an estimated $15m extra cost to achieve the original 80 per cent target.

A new, public report, prepared for Thursday's Operations and Monitoring Committee meeting, said the next council would receive a 'comprehensive package” of information about the museum, including tender pricing, additional funding and options for how to proceed with the project – including abandoning it.

It revealed the council resolved to accept a 70 per cent New Building Standard at the April 14 meeting, and the decision had not compromised existing funding – something that had been flagged as a risk in the confidential report.

New Building Standard is a way of measuring a building's seismic performance relative to a new building.

The report for Thursday's meeting said while a new structural design was more cost-effective - saving about $10m – the costs of the project were estimated to exceed the current project budget by between $18m and $20m.

It was due to Covid-related supply chain issues, and a higher contingency, it said. Some 'targeted” groundworks would also be required at an estimated cost of $3m to $5m, it said.

The report said the numbers were 'estimates” and would 'become more accurate” as the project neared completion and contractor pricing happened.

If new funding was not secured, a staged re-opening would require an estimated 'up to $5m” more, the report said.

However, it would ensure the whole museum was 'restored to a safe building standard,” was able to open to the public, and would buy the council time to raise funds to finish the remaining parts.

The report said to progress that approach would likely require community consultation as it would affect project outcomes, level of service and differ from earlier community engagement.

In the April meeting, councillors decided that decisions about the next steps should be made once tender costs were confirmed and discussions with funders complete.

The report said the council had since finished discussions with its four major funders – the Government, through the Provincial Growth Fund ($17m), and the Ministry of Culture and Heritage ($5m), as well as the Rotorua Trust ($10m) and the Lotteries Grants Board ($6m).

It said all funders accepted the reduced New Building Standard percentage but no single funder was able to cover the estimated shortfall of the project, although there were 'indications” some additional funding may be available.

Discussions would likely conclude at year-end, it said.

Government funders had indicated support for a staged re-opening if needed, and the Rotorua Trust and Lotteries Grants Board were yet to confirm.

"If they are also supportive this provides a viable option to move forward with certainty that a strengthened building and museum will be provided, albeit potentially with delay to the full internal fit-out.”

-Local Democracy Reporting is Public Interest Journalism funded through NZ On Air