The 1887 French renaissance-style building at Auckland Art Gallery Toi o Tāmaki requires urgent repairs costing millions of dollars.
Without the work, the category 1 historic building would have to be wrapped in a protective cover to reduce the risk to pedestrians from falling slate tiles on the steep pitched roof, and leaks to precious artworks.
Other problems with the building include condensation issues with wooden windows walled off to create internal spaces and paint on the original stonework.
In a statement, the council-controlled organisation that oversees the gallery said the heritage restoration works are expected with a building of this age.
"There has not been a sudden failure, but rather progressive deterioration.
"This has now reached a point where it needs comprehensive attention," said the statement from Jonathan Wilcken, director of strategy at Auckland Unlimited.
An early estimate for the restoration work is $10 million to $12m, he said.
The cost could rise when Ignite Architects and heritage experts Dave Pearson Architects complete a detailed report on the restoration project.
Wilcken said temporary works are being done to ensure any risk is mitigated before it becomes a problem. These works are due to be finished in the next week.
"The full roof restoration will remove any such risk for decades. The artworks are under no risk at present as the roof coverings are not leaking at this point," he said.
The main restoration project is planned to begin in the middle of the year and take about two years. It is likely some areas of the 1887 building will need to be closed during the restoration works, Wilcken said.
Arts patron Dame Jenny Gibbs, who has a long association with the gallery and sits on its advisory committee, said the gallery had been under-funded for repairs and maintenance for years.
She was not surprised at a statement by Wilcken that the roof slates were due to be renewed during a $121m upgrade and expansion of the gallery between 2008 and 2011, but that part of the project was deferred.
Gibbs said there was never an adequate budget for the project, which involved earthquake proofing and restoring the 1887 and 1916 parts of the gallery and adding complementary and contemporary additions.
"You can't have a gallery with leaks. A leak in a private house is one thing. A leak in a gallery with valuable works of art is a whole different matter," she said.
In 2018, Gibbs took part in Save Our Gallery to stave off a financial crisis at the gallery, which holds arguably the most extensive collection of New Zealand and international art in the country.
After years of Auckland Council progressively cutting the gallery's operating budget from $12m in 2012 to $6.9m, Mayor Phil Goff agreed to give the gallery an extra $2m a year in 2018.
Late last year, Auckland Unlimited informed Mayor Phil Goff and councillors that under a highly constrained scenario for the new 10-year budget, the 1887 building would have to be wrapped for three years as urgent restoration works are deferred again.
The CCO put forward an alternative scenario to fund the works, which has been included in the draft budget and expected to get the green light.
Wilcken said the restoration work was initially budgeted to proceed in the current financial year, but it was decided it could be safely deferred to the following year to help relieve the council's Covid-driven budget pressures.
The Herald sought comment from former gallery director Chris Saines - the driving force behind the award-winning upgrade of the gallery in the late 2000s - about what he knew at the time about the condition of the 1887 building.
A spokeswoman for the Queensland Art Gallery and Gallery of Modern Art, where Saines is the director, said he was not available for comment.
The slates were due to be renewed during the major extension project, but this part of the larger project was deferred. Minor repairs to the roof have been conducted in recent years to extend its longevity, but it has now reached the point of needing full replacement. There are issues with the roof fixings, likely a combination of the nails corroding and roof battens having come to the end of their life. The lead flashings have also become porous.
At some point in the building's history the windows were walled off internally to create usable internal spaces. The resulting sealed and unventilated void has caused long-term condensation problems, resulting in gradual deterioration and unsightly discolouration.
External façade painting
As with any building, periodic renewal of external paint is required. In this case, an appropriate paint coating provides a measure of protection for the exterior heritage fabric of the building.