Liberty Mutual wants to take over an entire city block in Back Bay, and three old buildings standing in the way are now slated for the wrecking ball. The insurance giant has proposed an 85,000-square-foot headquarters expansion that would add a new 10-story tower alongside its existing 22-story office complex at 157 Berkeley Street, consolidating its Boston employees onto a single block bounded by Berkeley and Stuart streets and Columbus Avenue.
Liberty Mutual notified Boston planning officials of the proposal, according to Banker & Tradesman, which reports the plan centers on a new 10-story, 62,000-square-foot tower plus a 23,000-square-foot addition to the current headquarters tower. To make room, the company plans to demolish three buildings: 304-308 Stuart Street, 135-137 Columbus Avenue and 139-145 Columbus Avenue, which the outlet describes as the last three undemolished parts of a triangular block carved out between those three streets.
The most recognizable name inside those buildings is Mooncusser, the seafood restaurant that Banker & Tradesman identifies as the trio's most prominent tenant. The five-story building at 135-137 Columbus Avenue dates to 1919, while the four-story structure connecting at 139-145 Columbus Avenue goes back to 1881, according to the Boston Globe. If approved and built, the project would expand Liberty Mutual's current headquarters footprint to occupy the full city block, per the same Banker & Tradesman report.
Consolidating a Workforce Split Across Stuart Street
Liberty Mutual already operates on both sides of Stuart Street, with part of its workforce housed in a building connected to the main tower by a glass-enclosed pedestrian bridge, the news outlet reports. As NBC Boston reported, the company told the Boston Business Journal it will consolidate all headquarters employees into that single block. The Boston Business Journal adds that Liberty Mutual plans to market two other buildings for lease as part of the shuffle.
Liberty Mutual spokesperson Glenn Greenberg described the expansion as establishing the company's workplace “for the next 100 years,” according to the Globe. The company may also ask the city for a zoning change tied to a signage program for the headquarters complex, the same report notes — a request that would run through Boston's existing sign rules. Back Bay Architectural Commission guidelines state that construction, features and signage not dimensionally or otherwise compliant with the Boston Zoning Code, including the Boston Sign Code, require a Conditional Use Permit from the Zoning Board.
A Rare Expansion Amid High Office Vacancy
The proposal lands at an unusual moment for Boston's office market. Citywide vacancy stood at 23.6% at the end of the second quarter of 2026, though the city also logged 590,938 square feet of year-to-date positive net absorption through that quarter — the first consecutive quarters of occupancy gains since 2019, according to JLL. The downtown core alone added 241,860 square feet of positive absorption in the second quarter, JLL reports, its second-best quarter for occupancy gains in four years.
Back Bay itself has outperformed the broader market. The submarket posted the city's lowest office vacancy rate last quarter at 15.9%, according to Bisnow, which also reported that Class-A offices in the central business district and Back Bay recorded 97,000 square feet of positive net absorption in the first quarter even as Class-B and C buildings lost 125,000 square feet of occupancy. Colliers data cited by Banker & Tradesman put Back Bay's third-quarter office availability rate at 16.7%, with nearly 223,000 square feet of positive absorption that quarter and more than 767,000 square feet absorbed year to date. Boston office-market executives told Bisnow the region remains “under-demolished,” pointing to a stock of obsolete buildings that have yet to come down.
Other Back Bay Towers Have Stalled
Liberty Mutual's willingness to build fresh stands out against other stalled Back Bay projects. Skanska received approval in 2024 for a large office tower at 380 Stuart Street but had not broken ground by the time of Banker & Tradesman's report, and BXP said in 2024 that it was putting its approved tower above the Back Bay Station parking garage on hold indefinitely, per the same outlet. Elsewhere in the submarket, BXP has instead poured $40 million into an amenities center at its 200 Clarendon Street tower, Bisnow reported, while law firm Weil Gotshal expanded its space by 33% at 1001 Boylston Street in the second quarter, according to JLL.
This would not be Liberty Mutual's first major Back Bay build-out. The company opened its 157 Berkeley Street headquarters in 2013 after a $300 million development, the Globe reports, following permitting that began back in 2010 for a planned 22-story, 590,000-square-foot tower that also included 205 below-grade parking spaces and preservation of 330 Stuart Street, according to Banker & Tradesman's earlier coverage. That 2010 plan also called for a two-story, 25,000-square-foot addition at 30 St. James Avenue. The new proposal still has to clear Boston's planning review process before any demolition or construction can begin.
