Four options have been revealed for the repair of the Rotorua Museum, but it could be three months before it's known how much each will cost.

At a Rotorua Lakes Council operations and monitoring committee meeting yesterday council chief financial officer Thomas Colle presented the four "seismic design" options.

The iconic museum building, which is more than 100 years old, closed indefinitely last November after being damaged by the 7.8-magnitude earthquake that struck Kaikoura. A subsequent seismic assessment found most of the building at 15 per cent of the National Building Standard. Buildings that are at 33 per cent or below are considered earthquake-vulnerable.

The four options included a range of repair methods from the complete deconstruction of the museum's north wing to replacing the building's heavy roof or installation of steel frame structures within the unreinforced walls.

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Mr Colle said although option one, to completely deconstruct and rebuild the older part of the building, would provide the most long-term benefit it was also "by far" the most expensive option.

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"It is probably the strongest you could get it, because you could build it 100 per cent to code, but that obviously has some significant costs attached.

"There is also the fact that you are demolishing the last heritage part of the building and that probably may not be palatable to the community and may not be palatable to Heritage New Zealand, but it is an option."

Option two addresses the components of the old building which are problematic.

It would see the replacement of the roof with a lightweight alternative, the replacement of the concrete walls, in the basement a glass wrapping of the columns and the placement of a subfloor beneath the existing floor.

"Under this option it would be trying to remove the concrete walls which are the weaker point and replacing them with steel alternatives," Mr Colle said.

"It doesn't resolve some of the other long-standing issues that the building has."

Mr Colle said option three was similar to option two.

"Rather than replacing those concrete walls it is looking to reinforce them with steel structures."

It also does not include the replacement of the roof.

Option four, the preferred option for the repairs to the Rotorua Museum. Photo/Supplied
Option four, the preferred option for the repairs to the Rotorua Museum. Photo/Supplied

"Option four is the one that we are working towards and I think is recommended by the engineers as well," he said.

The key difference from option three is the replacement of the old, heavy roof with one that is about one-fifth of the weight.

"As you can imagine when you have a very heavy roof the structure has to be a lot stronger, so by lightening the roof you do not have to strengthen those internal walls as much," Mr Colle said.

"Option four, by far probably retains the best balance of retaining the heritage, bringing the building to where it needs to be and addressing some of the historical issues."

Mayor Steve Chadwick said her first thought was the costs.

"Also, you haven't got up there [as an option] 'do nothing', not that that's an answer for me, but if we do go out to community, it would be good to see the level of community support for whether we invest in this.

"The base assumption is that we're going to fix it, which I think is what all councillors feel, but we haven't heard the costs."

Mr Colle said he wouldn't be making any estimates as to the cost, but they were talking multiples of $10 million.

"Option one would be by far the most expensive, option two and three would be the cheaper options and option four is somewhere in the middle."

The council aims to have costs for the options within the next three months.

Ms Chadwick also asked what was happening with the insurance.

"Insurance is still a tricky one," Mr Colle said.

"We obviously still need to quantify the costs of repairs."

This is only step one of the three stages the council will work through before any construction on the building starts.

The benefits will be weighed up against the operational costs for each of the repair methods and will go to public consultation.

"Because of the significance of this building there will be some form of public consultation and engagement on the options," Mr Colle said.

Following the selection of a seismic design the council will address the strategic direction for the building and ensure all requirements are in place before it is approved for construction.