Somerville lawmakers and planning officials are weighing citizen-led proposals to tighten rules on backyard cottages, pitting neighborhood concerns over vanishing green space and soaring home prices against state housing mandates.
Four citizen petitions aimed at amending a section of the city’s zoning code were heard at a Nov. 5 public hearing held by the City Council’s Land Use Committee and the Planning Board. The joint bodies had to rehear the proposals after earlier versions expired without a council vote before a statutory deadline.
Each petition carried the signatures of at least 36 local voters and was spearheaded by longtime former city councilor Bill White and former state representative Denise Provost.
Under Somerville’s zoning code, a backyard cottage is a detached single-family home built behind an existing home – often a triple-decker – with setbacks as narrow as 10 feet between buildings and 3 feet from side and rear property lines.
Provost said allowing full-scale homes on tight urban lots compounds crowding in a city already strained by development.
“They are vastly increasing the density of wooden houses in what is already the most densely populated city in Massachusetts and in all of New England,” Provost said. She noted that Somerville’s housing stock has shifted heavily toward condominiums since 2000, turning traditional owner-occupied two- and three-family homes into renovated market-rate units.
For local officials, however, rewriting local rules is complicated by state-level housing mandates. Councilor-at-large Ben Wheeler said binding state regulatory guidance restricts municipalities from imposing dimensional rules on accessory dwelling units that do not also apply to main residential structures.
“This is sort of intended to keep localities from saying, ‘Fine, you can do backyard [accessory dwelling units], but they can only be zero feet wide,’” Wheeler said. “The full implications mean we are not sure how to keep the ADUs from being just like a second building.”
Developer incentive
That regulatory overlap has also created financial incentives that city officials did not anticipate. Under Somerville’s inclusionary zoning rules, a developer building a traditional four-unit residential structure must include an income-restricted affordable unit. Under current guidelines, however, a developer can build a three-unit triple-decker and add a fourth unit in a backyard cottage without triggering that affordability requirement. Wheeler said developers naturally seek to build the largest backyard cottages allowed, which raises a property’s resale value and can encourage owners to tear down older, naturally occurring affordable rentals.
“Increasing the potential sale value of a property does often make it more likely that people are going to be displaced,” Wheeler said. “So that’s a tension that we’re really feeling here.”
City permit records suggest those redevelopment pressures are already playing out across Somerville. According to a Planning Division review of building permits issued between January 2022 and July 2026, the city approved approximately 50 permits for internal and external accessory dwelling units.
Of those projects, roughly 18 involved substantial work on the main building – either constructing a new primary structure or rebuilding more than half of the existing home – while another seven involved smaller renovations, according to senior planner Kortney Cena, who noted the estimates were compiled from an individual review of permit files.
Unintended consequences
Somerville resident and local activist Victoria Antonino, who spoke at the hearing, said backyard cottages were envisioned originally as modest spaces for multigenerational families or aging relatives. Instead, she said, oversized builds are pricing out longtime renters and shrinking private yards.
“These backyard cottages that aren’t cottages – they’re million-dollar homes,” Antonino said. “The intention behind accessory dwelling units was to make Somerville more livable, and it is now ousting a lot of people who make Somerville great.”
Antonino also raised concerns about stormwater runoff and lost tree canopy on small lots, noting that developers frequently rely on permeable pavers rather than green yards to meet the city’s landscaping requirements.
The Land Use Committee and Planning Board took no final votes at the hearing. With the public comment period closed, the bodies will move into separate working sessions to draft final zoning language before sending recommendations to the full City Council.
