Cathedral of the Blessed Sacrament NZ

Christchurch's quake-damaged Cathedral of the Blessed Sacrament will be revamped to the tune of $45 million over four years.

The diocese unveiled its plans for the cathedral, which involves saving the nave – the main central part of the church – and sealing off some other parts for potential restoration in the future.

Some areas, including the sanctuary, cannot be saved.

The church has been off limits since the February 2011 earthquake. It had a date with a demolition ball as recently as last year until a last ditch salvage plan was hatched. Diocese representatives met with architect Sir Miles Warren, who suggested the focus on preserving the nave.

"We then sort of did a complete backflip," Cathedral management board chairman Lance Ryan said.

"[Warren] said, 'It is worthwhile exploring as long as it's financially viable'. We got outside and thought we should at least give this a crack."

Bishop Barry Jones said the reversal was a welcome one.

"No bishop wants to be faced with the possibility of having to pull down his cathedral.

"I hope that you will realise how happy I am today to have this news to convey to… the people of the church and Christchurch."

The plan is not a guarantee. The diocese will soon apply to the Canterbury Earthquake Recovery Authority for a section 38 notice to start deconstruction and expose the nave. Only then will a close inspection be possible and its fate known.

"We may find that when we get in there that it's not possible to save it," Ryan said.

"[But] at least then we would have given it a complete try."