Liberty Mutual Insurance is planning to expand its headquarters in Boston’s Back Bay neighborhood, proposing a significant development that would consolidate its offices and adapt its facilities for future needs. The company submitted a proposal last week to the Boston Planning Department outlining plans to construct a vertical addition on an existing wing of its 22-story tower at 157 Berkeley Street, as well as a new 10-story building near the intersection of Stuart Street and Columbus Avenue. The project would involve demolishing three nearby brick buildings to create a unified campus designed to serve the insurer for the next century.

Liberty Mutual has described the expansion as an opportunity to “reimagine” its Boston presence, aiming to centralize all employees and operations into one consolidated block. A senior company official highlighted the intention to create a seamless workplace environment that supports both current and emerging conferencing and operational needs. While the exact height of the vertical addition remains unspecified, the plan includes seeking potential zoning changes related to signage, which might result in a prominent corporate sign visible across the Back Bay skyline, akin to the nearby John Hancock building.

The proposed development comes amid challenging conditions for the office real estate market in Boston and nationwide. Vacancy rates in Greater Boston stand at approximately 23.6 percent, although demand has largely been concentrated in premium Class A office spaces similar to those Liberty Mutual would be creating. Industry experts note that new office projects are increasingly tenant-specific rather than speculative, given high vacancy levels, construction costs, and interest rates.

Local officials have welcomed Liberty Mutual’s continued investment, recognizing the company as a major employer and economic anchor in the city. A spokesperson for Boston’s Planning Department expressed enthusiasm for the project and confirmed the proposal would undergo a community vetting process. The insurer previously developed the current headquarters building, which opened in 2013 at a cost of $300 million, supported by more than $46 million in state and city tax breaks at that time. It remains unclear whether the current expansion plan would affect existing tax-increment financing agreements, which are set to run through fiscal year 2030.

Liberty Mutual has not disclosed details such as the estimated cost or development timeline for the new project. The company also declined to confirm whether it would seek tax incentives to help finance the expansion. The project design is expected to complement the distinctive architectural form of the existing headquarters while responding to the surrounding urban context. With its century-long history in the Back Bay, Liberty Mutual’s proposed expansion underscores the insurer’s commitment to maintaining and strengthening its presence in Boston’s evolving commercial landscape.