Tourists walk past a vacant retail space at 50 Congress St. in downtown Boston's Financial District in September 2022. Photo by James Sanna | Banker & Tradesman Staff / File
Boston developer and real estate attorney Patrick Mahoney has filed plans to turn a Post Office Square office building into dozens of homes.
An LLC controlled by Mahoney wants to convert 50 Congress St. in downtown Boston into 171 apartments, an attorney for the company wrote in a letter of intent filed with the Boston Planning Department this week.
The property is currently owned by Denver, Colorado asset manager Sagard Real Estate, which paid $79 million for the building in 2017 according to a Suffolk County deed.
The 188,705-square-foot building would retain the current roughly 6,700-square-foot ground-floor retail space, the letter states.
In total, 20 percent of the building would be set aside as affordable housing: 17 percent as traditional subsidized units and another 3 percent dedicated to Section 8 renters, under Boston’s affordable housing rules.
The notification letter states the project will comply with new downtown zoning, and thus won’t need discretionary approvals beyond Article 80 permitting and participation in the city’s office-to-residential conversion tax incentive program. Administrative approval for compliance with a groundwater conservation district will also be needed, the letter states.
If Manoney’s project eventually applies for the city’s office conversion tax incentives, which grant a 75 percent, 29-year tax abatement, it would mark the 22nd application and bring the total number of proposed units to 1,435 across 27 buildings. The largest proposed to date is Synergy’s 255-unit 294 Washington St. project.
Only four projects worth 251 units have been completed or are currently under construction as of publication time, but if all 22 were completed, they’d take nearly 1.5 million square feet of office space off the market at a time when 12.03 million square feet are either available for lease or vacant across Downtown Boston and Back Bay, according to research by commercial brokerage Colliers.
Mahoney’s project, if it goes forward, will sit next to another potential office-to-residential conversion. Another LLC controled by Mahoney and Paul and Sandra Edgerly bought the neighboring 12 Post Office Square/10 Liberty Square building in late 2024 for $10.2 million, with an eye towards a potential conversion.
