Authorities are standing by the three-year closure, arguing the fixes to the building are urgent, but critics say it is unjustified without an approved development application and community consultation.
Sydney's Powerhouse Museum will temporarily shut its doors to the public on Sunday evening after more than 35 years of operation in Ultimo.
The museum is due to undergo three years of renovations before reopening to the public in 2027.
It's a decision that has sparked both delight and outrage in the community.
The Powerhouse is Australia's flagship science and technology museum, attracting hundreds of thousands of visitors per year.
The museum building is outdated, run down and urgently needs repairs to protect the precious objects inside it from damage, according to the Powerhouse executive and the New South Wales government.
And the $250 million "heritage revitalisation", they argue, will transform it into a superior, world-class museum.
But a conglomerate of hundreds of Powerhouse workers, museum experts and enthusiasts, union members, and local residents say the closure is premature and unnecessary.
"The museum closure is completely unjustified," the Save the Powerhouse Campaign said.
A petition calling for a delay to the museum's closure has attracted more than 5,000 signatures online.
At the forefront of the backlash is the Powerhouse's founding director, Lindsay Sharp, who headed the institution for 10 years from the day it first opened in 1988.
Dr Sharp, who also directed London's Science Museum for five years, said he doubted the Powerhouse would reopen in 2027 as promised — given the government has not released a refurbishment plan and the museum has been closed before planning approvals have been given, and a construction contract signed.
"There's no plan. We cannot detect an engineering architectural renovation plan or an exhibit collection development plan," he said.
Dr Sharp said the museum should stay open to the public until a development application is approved and the second Powerhouse Museum is opened in Parramatta in 2025.
It's expected to take several months for the government to complete a consultation process before a development application for the Ultimo museum can be approved.
"Why would you close it? Especially when you don't actually need to do so. And certainly not until you've got plans accepted," Dr Sharp said.
Museum defends closure
The state government and the Powerhouse executive have stood by their decision, insisting the museum's closure from Sunday is urgent.
"The building has significant problems that must be addressed without further delay, including leaks from the roof and large cracks in several walls," NSW Arts Minister John Graham said.
Powerhouse chief executive Lisa Havilah said it was "critically important" that precious objects in the museum be removed as quickly as possible to avoid damage from mould and damp.
"We don't want to continue to operate and compromise the collection," Ms Havilah said.
Iconic objects that have sat inside the building for 35 years like the Catalina flying boat and the state's first train, Locomotive No.1, will be relocated to the Powerhouse's Castle Hill storage site, which opens as a museum on weekends.
The objects are expected to be moved back to Ultimo after the renovations are complete.
When asked if she could guarantee the Ultimo building would reopen within three years as a museum, Ms Havilah said: "The Powerhouse Museum will return as a fully functioning international-standard Museum of Applied Arts and Sciences museum that we can all be proud of."
About 200 people gathered outside the Powerhouse on Thursday to protest its closure.
The head of the public sector union, Stewart Little, said many workers believed the funding for the revitalisation project was inadequate.
The arts minister has pledged $250 million for the museum's renovations — half the amount originally promised by the previous state government.
But less than $120 million in expenditure has been allocated for the project over four years to 2026-27 in the latest state budget.
"They are not going move the Catalina, boats, aircraft and parts of spacecraft out of here and then bring them back in three or four years," Mr Little said.
"There's no way that they can fund that."
With no Refurbishment Plan or final costings publicly provided before the closure of the museum, Mr Little said there were concerns the government was not being up-front about its true intentions for the site.
"It seems to us that they're working on budgetary constraints and they're doing this because money's being diverted from Ultimo to the Parramatta Powerhouse project," he said.
There are two separate allocations in the state budget for the Ultimo and Parramatta museum sites.
The state government said the next state budget would allocate $250 million in expenditure to the Ultimo project over the next three years.
Critics are also concerned that delicate artefacts like the 169-year-old Locomotive No.1 train will be damaged as they're moved from Ultimo to Castle Hill.
"You don't move those kinds of objects," Dr Sharp said.
"That collection is one of the finest collections of science, technology, engineering, social history, and decorative arts that exists in the world."
Ms Havilah said she was confident the collection was in safe hands.
"We have one of the best collections teams in the world, who really are specialists in moving objects and caring for objects," she said.
Community consultations are due to take place from Monday, February 5 until Sunday, February 25.