IF REPLACING single-family zoning with two-family zoning sounds like a major change for communities across Massachusetts, in this case one plus one could equal three.
A provision included in the state Senate’s sweeping economic development bill passed on Thursday would legalize two-family homes on any residential lot in the Commonwealth. Add in the relatively recent legalization of accessory dwelling units and suddenly most lots in Massachusetts could, on paper, become three-unit parcels.
Lawmakers say the change isn’t a panacea for the state’s projected need to build 222,000 new housing units in the next decade, but it represents a serious step toward allowing more houses at more accessible prices for the young people fleeing to cheaper states.
In his eight years as Senate Ways and Means chair, Sen. Michael Rodrigues said one thing “always keeps me up at night.” That’s the data showing the number one demographic leaving Massachusetts is 25- to 40-year-olds.
As the Senate moved toward passage of the bill, Rodrigues cited Senate President Karen Spilka’s vow to “go all in on housing” as a chief motivation behind the move to allow two-family houses by right on any residential lot — a change that would be the death knell for single-family zoning in Massachusetts.
The state can’t build the way it used to, and “the numbers are stark,” said Sen. Julian Cyr, the chamber’s housing chair. In the 1980s, when the 40-year-old legislator was born, the Bay State was issuing nearly 1,700 single-unit housing permits every month, Cyr said as the Senate debated amendments to the bill. Today, he said, that has fallen to about 415 per month.
Duplexes, a type of “missing middle” housing, have been made “nearly impossible through the promiscuity of veto power at the local level,” Cyr said.
Sweeping minimum lot size requirements mean that single-family homes are required to “consume more land than it often needs to use,” he said. According to a recent National Zoning Atlas report on Massachusetts, Cyr noted, more than half of the single-family zoning provisions in the state require minimum lot sizes of 40,000 square feet, or about an acre, and a quarter require almost two acres.
“That means that one of the most expensive commodities in Massachusetts — land — is needed in enormous amounts for every single home that we build,” he said.
Some municipalities, over the past two years, have cried to the rafters that Beacon Hill has already effectively abolished single-family zoning. In a 2024 housing bond bill — the Affordable Homes Act — lawmakers legalized accessory dwelling units in any single-family zoning district.
These are smaller living units, shorthanded as ADUs or “granny flats,” that can now be built without needing a special permit as long as they fall within reasonable restrictions. And single-family zoning districts are defined in the ADU regulations as “any zoning district where single-family residential dwellings are a permitted or an allowable use.”
Almost all residential lots in the state allow single-family housing, while only 38 percent of residential land allows duplexes by right under current law.
Yet the ADU law transformed the vast majority of lots in the state into potentially two-unit parcels. At least, if one of the units is less than 900 square feet.
Amy Dain, the author of a Boston Indicators report on the first year of ADUs, said the Senate seems to be taking “a parallel approach and learning from their experiences” with ADUs when it comes to duplex zoning. Since the 1970s, Bay State advocates pushed communities to embrace ADUs, Dain said, but most Massachusetts cities and towns shrugged off the suggestion.
In 2024, rather than trying to persuade cities and towns to rezone, incentivize local rezoning, or mandate municipal rezoning that would still require long and laborious local processes, the state handed down a simple instruction: ADUs are legal.
Lawmakers “could, say, take another 10, 20 years to ask cities and towns to legalize duplexes,” Dain said. “We have learned that is not possible. You could spend 50 years on it and you would only see it at the margins.”
Under the duplex provision of the Senate’s economic development bill, the projects would still need to go through the same type of local design or permitting processes as single-family houses, but no city or town could require a special permit for building two units rather than one.
Backers note that this will not necessarily mean a sudden influx of multi-family homes, or lots with three detached units, but it would give developers and owners more flexibility to decide the best use for a property.
The pitch is garnering pushback as “well-intentioned” but a “significant erosion of municipal authority over local planning and zoning,” according to Adam Chapdelaine, executive director of the Massachusetts Municipal Association, which advocates for cities and towns.
As both the House and Senate versions of the economic development bill move into negotiations, horse trading will begin behind closed doors.
The fate of the duplex zoning change, which would need approval from the House, remains uncertain. Senators have spoken approvingly of several provisions in the House bill, like a proposal to make it easier to develop housing on religiously owned parcels, which could be used as leverage to push for the new duplex zoning.
