Property owners on most residential streets in Milton and Canton could gain the right to build a duplex on their lot without a special permit, under a provision in the Massachusetts Senate's economic development bill expected to reach the floor the week of July 21.

The measure would require every municipality in the state to allow duplexes as-of-right on all residentially zoned land. In Milton, where nearly all residential parcels are zoned exclusively for single-family homes, the change would be dramatic. Under the town's current zoning bylaw, a two-family house requires a Board of Appeals special permit and can only be built on a lot that sits between two existing multifamily buildings on the same side of the street, less than 100 feet apart.

Canton's zoning is somewhat more varied, but only a handful of the town's zoning districts currently permit two-family dwellings, according to data aggregator Zoneomics.

The Senate proposal would eliminate those barriers. Duplex projects would still be subject to site plan review, septic system requirements, and local design standards, but would no longer need a special variance, according to CommonWealth Beacon, which reported the provision on July 16.

"We have an extreme shortage of homes, throughout the Commonwealth, that's driving this cutthroat competition for housing," said Jesse Kanson-Benanav, executive director of Abundant Housing Massachusetts. "We really need every strategy to get the various homes at various price points that we need."

Kanson-Benanav's organization has pushed for even broader reform, advocating statewide zoning that would allow up to five units per lot where utilities can support it. He pointed to Maine and Vermont, which already allow up to four units as-of-right on lots with water and sewer access.

State Sen. Julian Cyr of Truro, a supporter of the provision, said the duplex policy would make smaller-scale new construction more affordable for the next generation of Massachusetts residents. He called it "a simple but incredibly meaningful reform."

Not everyone agrees. The Massachusetts Municipal Association opposes the mandate. Executive Director Adam Chapdelaine called it "a significant erosion of municipal authority over local planning and zoning," adding that durable housing solutions require partnership with communities rather than overriding local decision-making.

Milton has already clashed with the state over housing density. The town fought the MBTA Communities Act, which required transit-served municipalities to rezone for multifamily housing. The state Supreme Judicial Court upheld the law's constitutionality in 2025 in Attorney General v. Town of Milton. In February 2026, Milton's Planning Board, led by Chair Meredith Hall, voted unanimously to recommend the town's MBTA zoning feasibility analysis to the Select Board.

Even if the Senate passes the duplex measure, it would need to survive a conference committee reconciliation with the House version of the economic development bill, passed the week of July 7, which does not include the duplex provision.

The Senate vote is expected the week of Tuesday, July 21.