Wellington city councillors have unanimously signed off on an extra $19.3m to strengthen and refurbish the Town Hall.
The budget is now set at $112.4m from an initial estimate of $43m after it was closed in 2013, and costs have ballooned ever since.
But that price could increase even further during construction.
Councillors today also considered a contingency fund to account for that behind closed doors, due to commercial sensitivity reasons.
Mayor Justin Lester said the cost is the cost.
"I'm not going to put a figure on how much is too much, we will as a council address that in the future if new information comes to hand."
Lester thought every Wellingtonian would agree the town hall is the city's cultural and civic heart and is a taonga.
Councillor Brian Dawson said they were in a difficult position and there was no fundamentally good choice to make.
"This is not my preference but it is my reality… it is a dead rat that we do have to swallow so we may as well get on with the chewing."
The town hall is the city's most significant heritage building because many people have been to events there, councillor Nicola Young said.
As a 17-year-old she came out as a debutante at the hall. It was also where she went as a primary school child to hear a young Māori soprano who people said was going to go far.
"Kiri Te Kanawa was fantastic."
"We must be brave, we must get this building under way, let's have it restored, let's have it returned to be our city's heart," Young said.
Councillor Iona Pannett said it would bring life to an important civic place.
But the decision presented her with a conundrum because she doubted the move was good long-term planning.
The area is the most vulnerable in the city to climate change and earthquakes, she said.
"We are spending a lot of money for a building which is heavily compromised and won't last the distance over the long-term."
The ballooning cost has been put down to the complexity of the project and the busy construction market.
More detailed investigations into the conditions of the ground and building have resulted in changes to the design.
The Wellington construction market is currently the most expensive in the country, council meeting documents said.
"The experience and capacity for this type of complex strengthening project sits with a few large construction companies. Contractor willingness to accept risk has dropped following the collapse of, and heavy losses sustained by some of the country's most trusted contractors."
Since the Town Hall was closed for strengthening in 2013 the cost of the work has grown from $43m, to $60m and in 2017 it hit $90m.
This was never a project for the faint-hearted, council chief executive Kevin Lavery said.
Naylor Love has been selected as the preferred tenderer and the project is expected to take four years.
Construction could begin as early as next month.
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