Nearly 120 units in a 14-story building with a public outdoor plaza are set for a project to construct affordable housing above the West End branch of the Boston Public Library.

Details regarding the scope and specifics of the project at 151 Cambridge Street were shared by developers in early January through a document submitted to the Boston Planning Department as well as at a February 12 public meeting.

Co-developers Preservation of Affordable Housing and Caste Capital are planning to redevelop the existing one-story West End library branch into a 165-foot-tall mixed-use building containing two bottom floors for the library and 12 stories containing 119 income-restricted apartment units.

“Based on the comments tonight, I think the project is in really good shape, and I am looking forward to having this housing which is desperately needed in the city built,” State Representative Jay Livingstone said at the February 12 public meeting.

While the proposed building has generally been agreed to be bringing essential housing, all of it affordable, to the West End neighborhood, a public plaza planned for the front of the structure emerged as something of a sticking point during the meeting, due to concerns regarding security, drug use and sleeping at the outdoor site.

“We are aware of those problems in the area,” Preservation of Affordable Housing project manager Kristel Salinas said. “We are working to address it internally as well as with the library, and we will continue that engagement and those discussions as we progress through the design.”

Members of the development team said the plaza would serve as an opportunity to provide needed open space along Cambridge Street with an area that welcomes people from a busy pedestrian corridor. But some residents said the plan for the outdoor space did not address problems of drug use and sleeping present in public areas on the street.

Landscape architect Gigi Saltonstall of G2 Collaborative said the project is looking at “how to make seating inviting for people to perch, but not for people to loiter for too extensive of a period of time.”

The plan also aims to keep the plaza’s planting beds low and visible to prevent “hiding spaces” where people could gather, according to Saltonstall.

“We are aware that this is an issue and is something that we will continue to work on as we’re evolving the plans,” she said.

Construction for the project is anticipated to begin at the end of 2026 and to be completed in early 2029, according to Salinas.

The development will not create any new parking spaces, according to current plans.

Of the units in the proposed residential structure, 30 apartments will be available for households earning under 80% of the area median income, 49 for households under 60% and 40 units for households below 30%. For the library portion of the building, a space of approximately 19,000 square feet is expected.

A period of public comment and review for the development’s Project Notification Form, a document detailing the proposed project, ended February 21.