Planning Board recommends zoning changes on Massachusetts Avenue to allow up to 12‑story housing, 18 in Porter Square under PUD

CAMBRIDGE, Mass. — The Cambridge Planning Board voted 7–0 on Oct. 21 to recommend that the City Council adopt a zoning petition that would create three new base zoning districts along the Massachusetts Avenue corridor, allow taller residential buildings where projects provide active ground‑floor uses and meet urban design standards, and create a Porter Square PUD overlay permitting up to 18 stories under a special permit.

City staff said the petition is intended to implement the 2025 Mass Ave planning study. “This petition will most importantly implement the recommendations of the Mass Ave planning study,” Evan Spatrini, senior manager for zoning and development, told the board during the public hearing.

The petition would replace existing business districts that front the corridor with new Mass‑6, Mass‑12 and Mass‑18 (PUD) districts. Under the proposal, residential projects that include active nonresidential ground‑floor uses on the primary street could rise to 12 stories in the primary Mass‑12 district; residential‑only projects would be limited to 8 stories. In Porter Square, the PUD overlay would permit up to 18 stories for projects that meet PUD standards, including a minimum retail FAR of 0.5, a requirement for a grocery store, and at least 20% of lot area designated as public or publicly beneficial open space.

Why it matters: staff and the board framed the petition as an implementation step for Envision Cambridge and the corridor study and as a way to add housing capacity while promoting active street life. Daniel Mesplay, director of community planning and design, said the Mass Ave planning study was rooted in Envision Cambridge and a lengthy engagement process that included a working group, public meetings, focus groups and walking tours.

Key rules and design standards: - Height: baseline residential height increases to 8 stories; projects with active ground‑floor uses on the primary street could reach 12 stories; PUD special permits could permit 18 stories in Porter Square. - Setbacks and upper‑story transitions: 3‑foot front yard setbacks on Mass. Ave. primary streets; upper‑story setbacks above 8 stories with additional transitions toward adjacent residential districts (15 feet above 6 stories, 25 feet above 8 stories in transition areas). - Floor plates: floor plates are capped at 15,000 contiguous square feet above 8 stories to encourage tower proportions. - Open space: buildings up to 8 stories would not be required to provide open space; buildings taller than 8 stories must provide 15% of lot area as open space, with at least 10% required to be public or publicly beneficial. - Active uses: the petition defines “active uses” as uses that encourage pedestrian activity (retail, restaurants, many institutional uses such as daycares and libraries, and certain consumer‑facing offices such as dentists), and ties the height incentive to those uses on primary streets.

Review and applicability: The petition keeps many existing development review thresholds (projects over 75,000 square feet residential or 20,000 nonresidential require project review). Inclusionary housing, green building and other city standards still apply. Jeff Roberts, director of zoning and development, said staff and the law department would resolve technical cross‑references if related petitions affect the same ordinance sections.

Questions and public comment: Board members pressed staff on technical drafting questions (section numbering, measuring setbacks from lot lines vs. street lines) and on interactions with the Affordable Housing Overlay (AHO). Evan Spatrini and Jeff Roberts said the AHO remains in effect and that the petition expands the AHO “square” by redefining its boundary within the new PUD overlay, which could change where AHO projects could use their existing height allowances.

Urban design and implementation: City urban designers and staff described the height‑to‑street‑wall approach and stepbacks to preserve a comfortable public realm. Brian Gregory of the urban design team said the 1:1 street‑wall ratio and upper‑story stepbacks are a common urban design strategy to define public space while allowing greater height set back from the street. Melissa Peters, assistant city manager for community development, said the city has developed signage standards for publicly accessible private spaces and has encouraged “open to all” signage for new POPS (privately owned public spaces).

Board action and next steps: After discussion and public comment (more than 90 written comments on the Mass. Ave. petition were noted on the record), the planning board voted 7–0 to recommend the petition to the City Council. The ordinance committee is scheduled to take initial public comment Oct. 30 and to deliberate further on Nov. 13; any recommendation from that committee would then go to the full City Council for possible adoption, amendment or rejection.

What the petition does not decide: The petition sets zoning rules; it does not itself approve any specific development. Staff and several board members noted that market factors, financing, construction costs and site consolidation all affect whether projects will actually be built to the maximum allowable height.

Ending: The planning board’s recommendation sends the petition to the City Council and the ordinance committee, where refinement and edits are still possible. If the council adopts a different text or map, the planning board and staff said they expect follow‑up clarifying edits to make the ordinance consistent across affected sections of the zoning code.