Triple-deckers are a cornerstone of Somerville. From Winter Hill to Davis Square, you’ll find the three-story, three-unit homes sprinkled in between cozy two-families and traditional single-family houses everywhere.
And yet their ubiquity hides a baffling fact: a new triple-decker hasn’t been fully legal to build in the city — or across much of Greater Boston — in decades, following widespread bans of their construction. Now, prodded by a state law aimed at addressing Massachusetts’ housing crisis, Somerville recently removed key restrictions on triple-deckers, changes officials hope will lead to construction of the beloved structures.
Indeed, housing advocates say the Somerville City Council’s vote last month makes it the first city in the region to fully legalize Boston’s famous stacked housing type, which defines dense neighborhoods across the region’s inner ring of suburbs.
“I love triple-deckers,” said Matthew McLaughlin, a Somerville city councilor who led the effort. “We’re allowing more housing, but we’re also allowing a historical structure, a culturally significant structure, to be built again.”
While it is not clear how many new triple-deckers will sprout from the rules, if many at all, the vote represents an important moment for the region, which has had a complicated relationship with the structures ever since they were banned in most cities and towns in the early 1900s amid the anti-immigrant movement.
Somerville’s changes are in line with a national trend in which cities and states are looking to encourage more moderate-density housing by relaxing zoning rules.
The new rules are fairly straightforward: Any three-unit building is now legal citywide by right, without requiring special approval from city zoning boards, and some of the old rules that made them difficult to build are gone.
The city technically re-legalized triple-deckers during a zoning overhaul in 2019, but property owners could only build a triple-decker if it was next to an existing one, and if they made one of its three units income-restricted. A few city councilors at the time felt the restrictions, especially the ones requiring affordability, were important, McLaughlin said.
But since that rule passed, just three people pulled permits to build one of the structures. All three eventually backed away from the projects.
A driving force behind the recent change, councilors said, was the state’s MBTA communities law, which requires cities and towns to zone for more housing near transit. While suburbs like Newton and Milton have been embroiled in heated fights over whether, and how, to comply with the law, Somerville, an already densely populated city, saw relatively little controversy over its vote.
The law’s end-of-year deadline to submit new zoning to the state was the extra push Somerville needed to get the new rules across the finish line, officials said.
“We thought this approach just made sense,” said City Councilor Ben Ewen-Campen. “These new rules essentially just legalize what Somerville already looks like.”
Some councilors expect property owners may take advantage of the rules to tack a third unit onto existing two-family buildings.
Not everyone supported the change. At City Council meetings in recent months, some residents were concerned that the structures would eat up open space in the city or lead to overcrowding in already-dense neighborhoods.
More than anything, critics were concerned about the council removing the affordability requirement.
Somerville, a previously working-class city, has transformed into one of the most expensive places to live in Massachusetts. The median rent for a one-bedroom apartment there is $2,500, according to Zillow.
Some residents thought allowing buildings without any affordable units would worsen the problem, with developers building only at expensive rates.
But supporters of the change hope any new units, regardless of their price, will help boost the city’s housing supply and slow skyrocketing costs.
“We certainly heard what some folks were saying, but we tried the affordability requirement, and they weren’t getting built,” Ewen-Campen said. “This was the best way to give the city a shot at building some triple-deckers again.”
Somerville’s new rules could amount to something of an experiment, testing whether the structures can be resurrected as the beacon of affordability they once were.
In the late 1800s and early 1900s, triple-deckers were built in abundance across the region. They represented a unique opportunity for working-class families. The buildings were relatively dense and cheap to build, so families, often immigrant families, purchased the structures as multigenerational homes or to rent the other units for extra income.
Eventually, state lawmakers passed the Tenement Act in 1912, a local option rule to ban the structures with roots in the anti-immigrant movement, and many cities and towns adopted it in quick succession.
And in the decades to follow, particularly in the 1960s and 1970s, cities and towns tightened their zoning rules, and have been adding on layers ever since, making it all but impossible to build the triple-decker, said Jeff Byrnes, a member of the pro-housing group Somerville YIMBY (which stands for Yes In My Backyard).
The structures, though, have stood the test of time. In many neighborhoods, they are some of what housing advocates call the last “naturally occurring affordable housing,” which rent below market rates without government subsidies.
Odds are the new three-story structures won’t be nearly as affordable as their older counterparts, Byrnes said, because construction costs have become exorbitant and market rents are sky high. But the units might rent for cheaper than single-family homes and some new-construction apartments and condominiums.
“The idea is that we’re hoping to see more of these structures that so many people love,” Byrnes said. “They’re not going to be naturally affordable anymore, but it is going to mean more homes across the city, even if it is a modest number.”