Castlemaine's library is due to reopen the first week of November, as unexpected issues with the old sandstone foundations have led to minor delays on its upgrade works.
Library manager Jess Saunders said the engineers had since resolved the issue.
"With older buildings it's hard to predict what's under the floor and this means we'll be staying in the pop-up library at the Market Building for a few weeks longer than expected," Ms Saunders said.
The pop-up library will remain open until the works are finished.
"We'll need a few days to relocate our collection, set up the computers and shelves, check everything in and make sure we're ready to open," Ms Saunders said.
The $420,000 project includes upgrading the structural flooring throughout the library, and replacing the shelving with mobile shelves to make the library more accessible and flexible.
The new-look library will also have a new layout, more seating, an extra photocopier and two more public computers.
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