Key Points:

The $12.9 million refurbishment and preservation of St Patrick's Catholic Cathedral in Auckland has received a major funding boost.

Kevin Sherlock, the cathedral's business manager, said the ASB Community Trust had confirmed it would give $510,000 towards the restoration and strengthening of internal arches.

"This was a very significant contribution to the historic project," Sherlock said.

"This latest grant is in addition to an initial $1 million which ASB made to the project in 2004. The money was received in 2006 and helped get the project off the ground."

The cathedral project has funding of more than $10 million, he said.

The Wyndham St cathedral was shut in October 2005, when work was projected to cost $12 million.

But late last year, Sherlock and cathedral administrator Father Bernard Kiely said the job had struck problems and would cost nearer $12.9 million.

Four high arches at the intersection of the cathedral's transept needed extensive reinforcing and strengthening, and this was discovered only as work progressed, they said. The arches were weaker than first thought.

The central aisle was also found to have a concrete tiled floor hidden beneath carpet and linoleum.

Auckland City Council's heritage section said this flooring had to be preserved because it was an original 1880s design.

The cathedral is due to open later this year.