Tall, narrow, crowded together but somehow spacious inside, Boston’s three-deckers have stood the test of time.
They pepper Boston’s neighborhoods, providing the backdrop for movies like “Good Will Hunting” and “Black Mass.” They house family after family, generation after generation.
There were 26,466 three-deckers in Boston in 2012, according to the city’s Department of Neighborhood Development.
More than 24 percent of housing units are located in three- or four-unit structures in the city of Boston, according to 2014 figures from the US Census’ American Community Survey.
Such buildings account for the largest share of housing units in the city. And Boston leads the top 25 largest US cities in the share of the units, way ahead of second-place finisher, Chicago, which had 15.2 percent.
But as Boston expands, larger housing complexes, or those with 20 units or more, are popping up across the city’s skyline and accounting for a greater share of units. According to the new Census numbers, 24 percent of the city’s housing stock is located in these types of structures, an increase of more than a percentage point since 2005.
And the trend is not expected to stop. Boston officials expect the population to swell by more than 90,000 residents by 2030 and believe that 53,000 new units will be required to house them.
Most of that development will be in larger, denser housing complexes on the fringes of developed neighborhoods and near public transit, said Sheila Dillon, head of the city Department of Neighborhood Development.
Dillon said few new three-deckers are expected to be built in the future, though the city encourages people to live in existing ones by offering home repair and downpayment assistance programs.
“In the last 50 years, none of that [triple-decker] housing has been built. Instead, it has been high-rise apartments, especially luxury ones,” said Barry Bluestone, founding director of the Dukakis Center for Urban and Regional Policy and a professor at Northeastern University.
Three-deckers, also known as triple-deckers, were first built in Boston’s “streetcar suburb” neighborhoods, such as Dorchester and Jamaica Plain, in the late 19th century. The three-story rectangular structures, which prided themselves on having windows on all four sides, offered a chance at upward mobility for Irish, Italian, and Jewish immigrants living in the city’s dark, crowded tenements.
Historically, three-decker owners would live in one unit and rent out the two others to help meet mortgage costs. In some cases, apartments would be let to other family members.
“It’s a really useful form of housing,” said Sally Zimmerman, senior preservation services manager at Historic New England. “It’s obviously dense and includes the basic minimums of a middle-class standard of living,” such as a living room, dining room, kitchen, bedrooms, and a bathroom.
In recent years, the demand for the properties has grown, and the population living within them has shifted.
Many have been snatched up by investors and turned into condominums. According to a 2014 report by The Boston Foundation, the price of a three-unit building went from $244,000 in 2009 to $452,000 in 2014 — an 85 percent increase in five years.
Increasingly, the units in three-deckers are being occupied by young adults, according to the report.
Bluestone sees that as a problem affecting the character of the city.
“You get three or four people in their twenties who pool incomes and can outpay every working family around,” said Bluestone. “You’re seeing the displacement of working families out of housing that was built for them.”
Concerns about the issue inspired a rally in Dorchester Saturday, where activists decried the displacement of low-income residents and communities of color from their neighborhoods due to rising housing costs.
Bluestone suggested “millennial villages,” a housing option in some European cities that features small apartments and communal amenities. Attracting young people to these units would free up the three-deckers for families, he said.
Another demographic group that is taking up residence in this type of housing are students, said Dillon. The city is working with colleges and universities to expand the amount of on-campus housing in hopes of reducing the demand for three-decker units, she said.
As Boston continues to grow up around them, three-deckers will remain a mainstay of family housing, Dillon said.
“I don’t see it changing all that much,” she said. “It actually works pretty well. Triple-deckers were ahead of their time.”Catherine Cloutier can be reached at email@example.com. Follow her on Twitter at @cmcloutier.