The Central Library’s $78-million renovation was completed while the building was operational. Maintaining library hours throughout construction was one of the project’s biggest challenges.

Located in Boston’s historic Copley Square, the library consists of two buildings, constructed 77 years apart. Each was named after its celebrated architect. The Charles Follen McKim Building opened in 1895. An addition, known as the Philip Johnson Building, opened in 1972.

The scope of work opened the previously inward-facing Johnson Building to Boylston Street. Once closed off by tinted windows and a series of granite screens, or plinths, the space—now filled with light—extends the library into a public plaza. The full-height curtain wall facade, transparent windows, multiple entries and new landscaping make the library feel as if the building is an extension of the sidewalk on Boylston Street. Inside the front door, there is a new space for events and other library programs, which unifies the library’s two buildings. The renovation increased ceiling heights and removed both internal load-bearing walls and external granite plinths along the street. A second-story window provided access during the first phase. That kept outside construction activity at the back of the building. During the second phase, a temporary pedestrian tunnel was installed from Boylston Street into the Johnson Building’s Deferrari Hall.

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