Liberty Mutual Plans Back Bay HQ Expansion With 10-Story Addition

Liberty Mutual has filed plans for a roughly 85,000-square-foot Liberty Mutual headquarters expansion in Boston’s Back Bay that would tear down three small brick buildings on Columbus Avenue and Stuart Street, add a new 10-story building and stack more space on its 22-story tower at 157 Berkeley St. The insurer outlined the project in an Oct. 14 letter to the Boston Planning Department, The Boston Globe reported on Oct. 20.

The Plan at a Glance

According to the project’s Notice of Project Change on the Boston Planning Department’s site, the expansion has two connected pieces:

• A vertical addition of about 23,000 square feet above the eastern wing of the existing 157 Berkeley St. headquarters.
• A new 10-story building of about 62,000 square feet on the lot just east of the tower.

To clear room for the new building, Liberty Mutual plans to demolish 304-308 Stuart St., 135-137 Columbus Ave. and 139-145 Columbus Ave., Banker & Tradesman reported. The trio are the last three older buildings left on the triangular block bounded by Berkeley Street, Stuart Street and Columbus Avenue. The best-known tenant in the three buildings is the seafood restaurant Mooncusser, according to the trade publication. The plan also calls for “improved open space” on the site.

The project is at an early stage. Liberty Mutual declined to share a cost estimate, a construction timeline or whether it will seek city or state tax breaks, the Globe reported. The company intends to seek approval through an amendment to the planned development area that allowed its current tower, according to Banker & Tradesman, and the proposal still has to go through the Planning Department’s development review.

Why Liberty Mutual Says It Wants One Block

“We’re thinking strategically about what we’ll need in the future, and over the next few years we will consolidate all employees and facilities at our headquarters into this one block of property,” Liberty Mutual spokesperson Glenn Greenberg said in a statement to the Globe. Senior Vice President Joseph M. Amante wrote in the letter to Chief Planner Kairos Shen that the project would provide a “seamless workplace experience” for employees and support conferencing and operational needs.

The Boston Business Journal reported that the company will no longer occupy 175 Berkeley St. and plans to market two other buildings for lease as it consolidates. Amante’s letter also said Liberty Mutual may seek a zoning change tied to a “signage program,” which the Globe said could mean a sign visible across the Back Bay skyline, similar to the John Hancock sign on neighboring 200 Berkeley St.

The Office Market Backdrop

The filing lands while Boston’s office market is still soft. Greater Boston’s office vacancy rate stands at 23.6 percent, down one percentage point from a year ago, according to Colliers data cited by the Globe, and no sizable office space is under construction in Boston proper. Colliers research director Jeffrey Myers told the Globe that trophy Class A buildings have the highest rents and lowest vacancy rates, while speculative projects “are going to be really hard to pencil.”

Back Bay has held up better than other districts. Colliers put the neighborhood’s availability rate at 16.7 percent in the third quarter, with about 223,000 square feet of positive absorption in the quarter and more than 767,000 square feet so far this year, Banker & Tradesman reported. Other big Back Bay office plans have stalled: Skanska won approval for a tower at 380 Stuart St. in 2024 but has not broken ground, and BXP shelved its approved tower above the Back Bay Station garage, the publication noted.

Liberty Mutual opened 157 Berkeley St. in 2013 as a $300 million project backed by more than $46 million in state and city tax breaks, according to the Globe. Its tax-increment financing agreement with the city runs through fiscal 2030, and it is not yet clear whether the new plan would affect that deal.

Early Reactions

Tamara Small, chief executive of the real estate group CREDA Massachusetts, told the Globe the plan “shows a real commitment to the city of Boston.” Planning Department spokesperson Brittany Comak said the city is “excited that they plan to continue their investment in our city” and will review the proposal “alongside the community.”

Our Take

This section is analysis, separate from the reporting above. A company consolidating into buildings it already owns is a very different bet from a developer building offices on spec, and that difference matters for downtown. Liberty Mutual is adding space for its own people while leaving 175 Berkeley St. and marketing other buildings for lease, which could put more square footage back on a market that is already crowded. The open questions are the ones the company has not answered yet: what it will cost, whether it will ask for new tax breaks while its current deal runs to 2030, and what happens to Mooncusser and the older brick buildings on Columbus Avenue. Those answers will shape how the community review goes.

For more on downtown real estate, see our coverage of the 100 Summer Street auction, the Motor Mart Garage sale and the lawsuit over 75 Morrissey Boulevard.

Featured image: The Liberty Mutual tower at 157 Berkeley St. in Boston’s Back Bay. Photo by Daderot via Wikimedia Commons, CC0.

Sources

• The Boston Globe: Liberty Mutual expanding Back Bay HQ, may add sign (Oct. 20, 2026)
• Banker & Tradesman: Liberty Mutual HQ Expansion Would Consume Full City Block (Oct. 20, 2026)
• Boston Business Journal: Liberty Mutual to demolish three buildings for new 10-story Back Bay tower (Oct. 20, 2026)
• Boston Planning Department: 157 Berkeley Street project page