In 2014, a plaster rosette fell from the 52-foot ceiling of the New York Public Library’s grand Rose Main Reading Room. The library was already closed, but the accident prompted the largest renovation of the library’s ceiling in its over 100 year history, a renovation that is nearly complete.

“When we first started the project the immediate concern was to determine why the one rosette had fallen,” says Gerry Oliva, the director of facilities management for the entire NYPL system. “But when we looked at that we started thinking, we have a building that has been open to public since 1911, and a ceiling that was, at the time, 103-years-old. So we took a step beyond and looked at the entire ceiling under fine-toothed comb to make sure it would be preserved for future generations.”

Two years and $12 million later, the renovation–which included reinforcing all 180 rosettes, removing asbestos dust, and recreating a mural in the adjacent catalog room–is complete. On October 5, the Rose Main Reading Room and Bill Blass Public Catalog Room, both located at the landmark 42nd street library, will reopen amid a larger $300 million renovation plan for the NYPL Midtown campus.

For the duration of construction, the Reading Room, which is about the size of a football field, has been covered in over a mile of scaffolding, its long wooden reading tables and signature brass lamps covered by sheets. The project, managed by New York-based Tishman Construction, involved the crew systematically sounding the ceiling for hollow spots, and conducting a vibrations analysis to test for areas where it was stressed.

A miniature electronic rail system will transport books on carts to pre-programmed spots throughout the library.

Structurally, the plaster ceiling turned out to be holding up well, so the crew focused on fixing cracks and restoring ornamental elements. They touched up paint in places, bonded the cracks with adhesive and installed a stainless steel aircraft cable that runs through the ceiling and ties back the plaster rosettes, keeping them suspended should another come loose and threaten to fall.

But prospects for the Bill Blass room, known for its 33-feet-wide mural of the sky painted by artist James Wall Finn in 1911, weren’t quite as positive: wear and tear, coupled with improper repairs over the years, left the original painting unsalvageable. EverGreene Architectural Arts, a New York-based firm that specializes in restoration, recreated the mural on canvas, then installed it in two parts over the original. Oliva notes that the canvas mural can easily be taken down if the library ever wanted to uncover to the original.

When the rooms open back up in a few weeks, they’ll be used for research and reading as before, though the library is also planning to offer laptop lending services and new collaborative spaces for researchers. Around the rooms, however, the library will start to change–part of what NYPL president Tony Marx calls the largest renovation in the library’s history. After a construction proposal for the research library eight years ago incited outrage because its plan to move the books from the stacks and into storage, the library has regrouped with a new $3 million plan. Now, the library is building thousands of new shelves under Bryant Park, and will be able to fulfill most of the research requests on-site.