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Insurance firm Liberty Mutual has notified Boston planning officials it will be proposing an 85,000-square-foot headquarters expansion in the Back Bay.
If approved and built, the project would expand its current headquarters to occupy a full city block.
The company plans to demolish 304-308 Stuart St., 135-137 Columbus Ave. and 139-145 Columbus Ave., the last three undemolished parts of a triangular block bound by Berkeley Street to the west, Stuart Street to the north and Columbus Avenue to the southeast. The trio of small prewar buildings’ most prominent tenant is the seafood restaurant Mooncusser.
In a notification letter to the Boston Planning Department, Liberty Mutual Senior Vice President Joseph Amante said the company wants to build an “improved open space” and a 10-story, 62,000-square-foot tower on the site of the three buildings it hopes to demolish, plus a 23,000-square-foot vertical addition above the eastern end of its current, 22-story 157 Berkeley St. tower.
“LMIG and its design team are developing the architectural expression of the Project to complement the form and material character of the existing Liberty Mutual building while responding to the surrounding Stuart Street and Columbus Avenue context,” Amante’s letter states.
The company already houses part of its workforce in a building it owns across Stuart Street from its tower, connected to the main building by a glass-enclosed bridge. Amante said the company is planning the expansion to “provide a seamless workplace experience for its employees; support contemporary and future conferencing and operational needs; and establish an enduring architectural presence” in the Back Bay.
The company plans to seek approval via an amendment to the planned development area that allowed it to build its 157 Berkeley St. tower in 2011.
The project also represents the biggest expansion of back Bay office space since Samuels & Associates’ Lyrik development opened on the neighborhood’s far western side in 2024.
Development and construction firm Skanska received approval for a large office tower near the Liberty Mutual campus, at 380 Stuart St., in 2024, but has not yet moved to break ground. Later that same year, major office landlord BXP told investors it was putting its approved office tower on top of the Back Bay Station parking garage on ice indefinitely.
Since then, the company has begun touting the strength of the Back Bay office market. Research by commercial brokerage Colliers pegged the Back Bay availability rate at only 16.7 percent in the third quarter, significantly below the city’s other major office districts and boasting nearly 223,000 square feet of positive absorption in the third quarter alone, and over 767,000 square feet of positive absorption year to date.
