Image courtesy of RODE Architects

A Brookline developer seeks to modernize and expand a former Iron Mountain records warehouse in Boston’s Newmarket district for a range of commercial uses including an 813-unit self-storage facility.

Brookline-based Bahlmann Capital Group is proposing a 6-story addition alongside the existing building at 134 Hampden St., creating a 105,607-square-foot building including office space, wine storage, self-storage and ground-floor retail space.

Boston planning officials have sought to encourage a wider range of commercial uses within the Newmarket district, while retaining its inventory of industrial space for companies such as food distributors that require proximity to clients in the urban core.

The 73,280-square-foot former records warehouse would be converted into a self-storage facility, including 434 square feet for a wine cellar, according to a project notification form submitted to the Boston Planning Department this week.

The addition would be built on the 120-126 Hampden St. portion of the site and include 24,000 square feet of self-storage on the second through sixth floors, according to the development submission. Other commercial uses would include office space on two floors and 3,665 square feet of ground-floor retail space.

The Hampden Street project is proposed under the Newmarket Creative Industrial Zoning subdistrict enacted in 2023, and the self-storage facility will require approval as a conditional use by the Boston Zoning Board of Appeal. The four-parcel site spans 0.67 acres.