Redevelopment and earthquake strengthening of Whanganui's Sarjeant Art Gallery is unlikely to finish in time for the gallery's centennary.

And that's not the only bad news.

Latest estimates put the cost of the project at $34.985 million - about $2.5 million above original estimates.

Gallery director Greg Anderson told a Whanganui District Council Property and Community Services committee on Tuesday that the gallery would most likely open again in 2020, one year after its 2019 centennary.


More exact timing would be known after a procurement plan has been commissioned and completed, he said.

But there was good news also.

The Sarjeant Gallery Trust was well on target to raise about $9 million needed to secure a $10 million Government grant. The trust has until December to raise the money before the Government grant offer is withdrawn.

"Hopefully it won't take until December," Mr Anderson said.

A strategy involving funding applications to public and private trusts, lotteries sources and corporations had so far been "very successful."

The next phase of the redevelopment was to commission a procurement plan. Two potential providers were to be approached to submit quotes.

If council agreed to proceed with the plan the project will have entered its final phase before a decision is made on retaining a principal contractor.