Anglican church leaders have agreed to reduce the seismic strengthening of Christ Church Cathedral to lessen a $114 million shortfall.
The cost of restoring the quake-damaged cathedral has blown out to almost $250 million.
Anglican Bishop Dr Peter Carrell said Saturday's agreement cut the funding gap to $85 million.
That shortfall assumed further fundraising and a contribution from the church. A proposal to inject $16.2 million by selling off church land and buildings was also agreed.
Carrell said the six-hour synod meeting reaffirmed the church's commitment to rebuilding the cathedral.
"We agreed to a funding pathway which could see $16.2 million of new funds injected into the cathedral project."
The recommendation by Christ Church Cathedral Reinstatement Ltd to remove other elements of the concept design was also accepted, he added.
"We also agreed to support the acceptance of some reduction in scope of the project, in particular that the seismic rating of the building might drop from a 100 percent of new building standard to 67 percent of new building standard."
CCRL chair Mark Stewart said he was heartened by the support from the synod.
"The project, as originally agreed [between the church, government, and council] is no longer attainable. The decisions made by synod will make a major difference to the overall project cost and demonstrate good will for upcoming discussions with council and government."
Carrell said the discussion was "robust at times but the synod as a whole was deeply engaged in every matter put to it" and he was "relieved" by the outcome.
He said the project could now finish two years earlier than forecast.
Original estimates put the completion date at 2031.
But Carrell said the cathedral's completion was still not guaranteed.
"I'm confident but there's no certainty until we know that we can bridge that particular $85 million funding gap.
"We will all need to work together. This is only the first element of a solution. We cannot do this alone."