Wellington's Central Library will close indefinitely after the city council received engineering advice about significant quake vulnerabilities.
The closure was effective from 8.30pm Tuesday, with no date set for its reopening. The carpark underneath the library would also close, as well as Clark's Cafe and Citizens Advice Bureau which operate inside the complex.
Wellington Mayor Justin Lester said the library was "the living room of the city" and it was a very difficult decision.
"I understand how disappointed Wellingtonians will be to have a cherished and much-loved venue close. It pains me too."
About 3000 people, including up to 500 children, visit the library each day.
An engineering assessment found there were "specific structural concerns" with the library's floor seatings.
"The building [has] a complex design with a flexible frame, large voids and irregular shape - all of these elements contribute to the building's structural vulnerability in a significant earthquake," the assessment found.
The report, which was given to the council on Monday found the library's precast floors were similar to those found in the Statistics New Zealand building which partially collapsed in the 2016 Kaikōura earthquake.
"We have acted as fast as we possibly could. It would be difficult to go any faster.
"We're not legally obliged to close this building, we are morally obliged," Lester said.
Council chief executive Kevin Lavery said it was an "obvious and necessary decision".
While the jobs of council staffers were safe, there were concerns for staff working at Clark's Cafe, an outfit which was not owned or run by council.
Murray Edridge, Wellington City Missioner, said the shock closure had taken the mission by surprise, and it would have a "huge" impact on Wellington's homeless community.
"Obviously it's a place of shelter and warmth, particularly in the winter months. If people are applying for jobs or doing CVs or having to connect to the world then internet connectivity is really important, that's one of the places they can most easily get it.
"Thirdly, and most importantly, it's a place of community, it's a place where you can connect with other people."
There would be "quite a major impact" on the homeless. Some library users would have alternatives, but there would be a "number of people" who would have none.
A "range of options" were now being considered for continuing library services in the central city, a council spokeswoman said.
The exit of staff, the building's other tenants, and "in slower time", the library's collection, would need to be carefully managed, the council said.
In the interim, people were being encouraged to use suburban library branches or the digital library service.
Items currently on loan from the central library would be automatically renewed, and fees for returning items to other branches would be suspended.
The library is the latest in a line of capital buildings that need seismic strengthening.
Last month, Wellington's Town Hall restoration budget blew out to $112 million.
Reading Cinemas on Courtenay Place was closed immediately due to quake risk in January.
LIBRARY CLOSURE - WHAT YOU NEED TO KNOW