The Boston Public Library is considering adding apartments to share space with four neighborhood branches slated for renovation, a rare combination that exists in New York and Chicago but would be the first in the city.

The initiative, being developed in collaboration with the Department of Neighborhood Development, fits with Boston Mayor Marty Walsh's drive to build more housing units as a way to moderate rising rents. The branches that could see public library patrons and private tenants in the same building are the West End near downtown, Fields Corner and Uphams Corner in Dorchester, and Egleston in Roxbury, according to one city official.

Taylor Cain, director of the city’s nascent Housing Innovation Lab, confirmed what is known as the Housing with Public Assets Initiative is looking into co-locating housing with branch libraries. She said the Fields Corner branch could become the prototype.

“This is very much still in the phase of testing proof of concept. We are currently doing this process in Fields Corner,” Cain said in an interview with WGBH News. “There’s definitely been conversations about what other library branches we should look to have this conversation at, and we hope that in the new year, we’ll be able to announce the next slate of library projects."

In Fields Corner, the mixed-use proposal is one of three options for the pending renovation of the small, aging building on Dorchester Avenue. That plan would add a second floor of library space and 36 privately-owned apartments on three floors above that one.

City officials said the idea was inspired by a past proposal from a Dorchester community development group, VietAid, and the similar projects in Chicago and New York.

David Leonard, president of the Boston Public Library, said leveraging city space to provide multiple functions on a single site seems appropriate for densely-populated Boston.

“It’s a better use of property,” he said in an interview. Leonard also pointed to a pending, larger project along Tremont Street that aims to combine a new Chinatown library branch with housing, hotel space and a parking garage in a 350-foot tall tower. Project documents estimate it will take until 2023 for multiple partners, including the Asian Community Development Corporation, a New York-based commercial real estate company, and Tufts University, to complete that mixed-use development.

Cain said the Chinatown proposal is separate from the initiative.

A preliminary rendering of the five-story, mixed-use building proposed in Fields Corner. Courtesy of Boston Public Library/Oudens Ello Architecture

“Simply because of density in the city, wouldn’t it make more sense to look at having mixed-use, rather than only doing a single- or two-story library on a stand-alone site?” Leonard said. WGBH News has a broadcast studio inside the main branch of the Boston Public Library in Copley Square.

The Fields Corner branch's building "opened in 1969 as the successor to the neighborhood's old Dorchester Branch," according to the Boston Public Library. Officials say the building is nearing the end of its useful life, but implementing the mixed-use proposal is complicated because state law bars the kind of public-private partnership it entails.

"Mixed-use facilities for public properties are not, at the moment, legal. So this would require special legislative approval," said Matthew Oudens of Oudens Ello Architecture, the firm tasked with leading the initial phases of the Fields Corner renovation.

At a November meeting at the library on its future, Boston City Councilor Frank Baker, who represents the area, expressed confidence that the state would grant an exception.

“We’re all experiencing this affordable housing crisis statewide,” Baker said. “If we as the City of Boston, the main economic driver in the state, went to the state and said we want to try something different, to use our assets that we own to try and alleviate some of the [affordable housing pressure] that’s on our neighborhoods … I think, and I could be wrong, I think the state would say ‘yes.’”

Baker said he envisioned the Fields Corner apartments being designated as senior housing, but wouldn’t push the plan if the community rejects it.

“This is a neighborhood that, potentially, is going to change in the next five, 10 years, so the need for housing is more pressing here,” he said. “This is us saying, ‘We want to believe in affordable housing. We want to try different models.’ This is a model here, and if we get this right, I think that this model will be replicated across the city.”

The proposal was met with a split opinion from the few dozen people who attended the meeting. Supporters argued the city's density and need for housing makes it a good idea. Opponents said it doesn't fit the neighborhood's character and represents a missed opportunity for better planning.

“Visually, the additional story just looks completely out of place with the rest of the neighborhood,” said Candice Gartley, executive director of the neighboring All DorchesterSports and Leadership youth organization. “People are coming in and they’re jamming stuff in on every square inch without asking what the neighborhood wants.”

The other two options for renovating the Fields Corner branch call for only the library — one plan proposes a single floor, and the other proposes two floors.

Others at the meeting complained the plan would further the exodus of families by creating more one- and two-bedroom units.

“I’ve lived in this neighborhood all my life,” one woman said. “I understand how Boston is changing and the makeup of who’s here is changing, but you keep putting single units in for individuals — where’s the families going?”

Others argued that the project and more like it are necessary to provide more housing and modernize the area.

“The city is an old city,” said Jacquie Bishop. “We can’t physically expand out. The only way the city is going to expand, and not have brain drain, and not have race-based brain drain, is if we build up and create housing and be creative in those ideas.”

Bishop explained that she and her wife are having trouble relocating from their third-floor unit nearby because of housing prices.

“It’s a new Boston. In the 17 years I’ve been here, we’ve gained 100,000 residents,” Bishop continued. “If we’re going to keep them, we got to figure out some other way, and that includes changing some of the footprints of neighborhoods.”

The debate about the library’s future is happening amid a $12 million renovation for the 50-year-old Fields Corner branch. The Boston Public Library system is also renovating several branches in other neighborhoods, including Adams Street in Dorchester, Dudley in Roxbury, Roslindale and the South End.

Cain said officials with the Housing with Public Assets Initiative are hoping to roll out a slate of library projects in January, “but we haven’t made any firm commitments for which library projects will be the next to move forward.”