The iconic main branch of the venerable New York Public Library is heading for a major update.

The library system's board of trustees voted unanimously to approve a $317M renovation of the Bryant Park-area building, a figure that accounts for $144M already spent on improvements over the past decade, the Wall Street Journal reports.

The plan will increase public space for study, exhibition and educational programming by 20%, partially accounted for by converting storage space. The library will also add a new interior entrance plaza and café, as well as convert a staff entrance on 40th Street to an additional public entrance to ease congestion.

The three- to four-year renovation will be devoted to balancing the building's dual purposes as a tourist destination and a learning institution by focusing gathering spaces on the lower levels and adding quieter areas for research on the upper levels. New bathrooms, an elevator and a Center for Research and Learning for high school and college students will also be coming to the library.

The marble exterior of the Beaux Arts-style building along Fifth Avenue in Midtown Manhattan, also known as the Stephen A. Schwarzman building, named after Blackstone's founder, will remain unchanged, as will the historic book stacks. A previous renovation plan that would have dismantled the stacks was abandoned after public outcry and a lawsuit in 2014.

All but $9M of the project's budget has been raised from private donations, and the library system plans to raise an additional $128M to replenish its $1.2B endowment. As for the stacks, there is no plan for their future as they currently hold the collection of books from the Mid-Manhattan branch across the street as it undergoes its own $200M renovation. The historic collection is currently housed in underground storage beneath neighboring Bryant Park.