Milton homeowners have already embraced a state law that lets them add in-law apartments, backyard cottages and basement conversions without asking the Zoning Board of Appeals for permission.

Milton approved 24 accessory dwelling units in 2025, ranking fifth statewide among the 217 communities that issued ADU permits in the law's first year, according to a state announcement in February 2026. Canton homeowners have the same rights under the law, though the town's permit totals were not listed in the state's top-10 data.

The 2024 Affordable Homes Act, signed by Gov. Maura Healey in August 2024 and effective Feb. 2, 2025, allows any single-family homeowner in Milton or Canton to build one ADU of up to 900 square feet, or half the primary home's floor area, whichever is smaller, by right.

No special permit, no variance, no public hearing required.

The units can be attached to the main house, built as a freestanding backyard structure or carved out of existing space like a finished basement or garage. Towns cannot require owner-occupancy, cannot mandate a family relationship between the ADU occupant and the property owner, and cannot require more than one additional parking space. Properties within a half-mile of a transit stop owe zero extra spaces, according to the state's ADU FAQ page.

Canton's own zoning was tested directly. The Attorney General's Office issued a decision on June 4, 2025, striking down Canton's attempt to impose a minimum lot size requirement for ADUs. As of Feb. 2, 2025, any local zoning provision that conflicts with the state ADU law is unenforceable.

What homeowners still need

"By right" does not mean paperwork-free. A standard building permit is still required, and the ADU must meet the Massachusetts State Building Code, Title 5 septic regulations and local setback requirements.

In Milton, estimated permit fees run $1,000 to $2,500, with a typical review timeline of about four weeks, according to the ADU Permit Navigator. Canton's fees range from $900 to $2,200 with a similar timeline. Homeowners should confirm current requirements with their building department: Milton at (617) 898-4847, Canton at (781) 821-5013.

Septic capacity is a practical barrier for homes not on town sewer. Adding bedrooms through an ADU can trigger a Title 5 system review and potentially a $25,000 to $40,000 upgrade.

Financing help available

MassHousing's Accessory Dwelling Unit Loan Program offers income-eligible homeowners up to $250,000 for detached ADUs and up to $150,000 for attached units. For Norfolk County, which includes both Milton and Canton, the income limit is $209,250, effective June 15, 2026.

The state also offers subsidized feasibility studies through the Massachusetts Housing Partnership, capping homeowner cost at $500 for a study covering property constraints, utility needs and a preliminary cost estimate. The Healey administration's free ADU Resource Center at MyMassADU.org lets homeowners enter their address to see what an ADU could look like on their lot.

Statewide momentum, local barriers

Statewide, cities and towns approved 1,224 ADUs across 217 communities in 2025. In the first half of 2026, the Healey administration reported 854 more approvals, according to CommonWealth Beacon.

Housing advocates say the numbers could be higher. "Massachusetts has layered countless rules around zoning, wetlands, stormwater, fire safety, energy codes, and local approvals into a system that is extraordinarily difficult for even experienced developers to navigate, let alone ordinary homeowners," Luc Schuster, executive director of Boston Indicators, said at a May 21 event on the law's first-year results, according to CommonWealth Beacon.

Milton's Master Plan Implementation Committee noted the ADU legislation in its October 2025 report to the Select Board and Planning Board as a change affecting the town's housing strategy. As we reported July 17, a separate Senate proposal to legalize duplexes by right could eventually allow most residential lots to become three-unit parcels if stacked on top of the ADU law. That duplex measure has not yet passed.

Homeowners ready to explore an ADU can contact their local building department or visit MyMassADU.org to start the process.