The First Presbyterian Church congregation will need community help to rebuild the Invercargill church, elder William Watt says.
A fire believed to have caused by an electrical fault broke out in the vast ceiling void below the copper roof dome last week.
Although the 100-year-old category 1 protected building appears undamaged from the outside, about 20% of the interior was affected by fire or water damage, Mr Watt, who chairs the First Church Heritage Buildings Charitable Trust, said.
As well as fire damage in the roof void, debris had fallen into the sanctuary - the focal point of the church which houses the altar and lectern - while smoke and water damage had ''completely ruined'' the just-completed paint job in the church.
It was also likely the ''very fine'' Rodgers 940 digital organ which sat in the sanctuary would be water damaged beyond repair, he said, although that was not yet confirmed.
Church members were ''grieving the loss of the church as it was'' Mr Watt said.
''They are thankful no-one was hurt and the fire wasn't worse, but it is still a significant blow.''
The church was insured and assessors had already visited, he said.
But he said it it would be ''certainly months'' before the congregation could use the church again.
''First the repairs have to be designed and costed. Then we have to work out how to pay for them.''
It was not expected insurance cover would meet the full cost of repairs.
Community help would be needed, he said, although he was unsure yet whether that would require a public fundraising appeal.
''What we have is a problem bigger than just for the congregation. First Church is not just a church, it is an Invercargill icon ... a stunning building.''
Interior renovations were nearing completion when the fire broke out. Mr Watt said the renovation budget was $250,000 but had grown to about $300,000 after the discovery of asbestos.
Renovation costs were met by grants from the Presbyterian Synod of Otago and Southland, the Community Trust of Southland and the Invercargill Licensing Trust (ILT) and ILT Foundation.
Mr Watt said it was too early to say whether further money would be sought from those organisations.
Sunday services have been held in adjoining Stobo Hall during the renovations. Mr Watt said that would continue, as the hall was not affected by the fire.
