Mother-in-law apartments — secondary units often built alongside, inside or in the backyard of a home — could pop up along the Green Line in St. Paul.

City Council members are considering whether to allow construction of those “accessory dwelling units” within a half-mile of the light rail line. Community members and city officials said the units could create more affordable housing and provide homes for seniors who want to age in their neighborhood but not maintain a large house.

“When you have a transit line, you want to have density that is supportive of transit ridership. And we have a lot of single family homes in that area, and we want to ­maintain those established neighborhoods,” Senior Planner Jamie Radel said, noting that accessory units balance those desires.

Minneapolis approved accessory units in 2014, and many suburbs also allow them. The units appear to be growing in popularity in cities and inner-ring suburbs over the past decade, Radel said.

St. Paul currently has strict rules about such units. It only allows carriage houses, defined as an accessory unit above a detached garage, in certain districts when specific conditions are met.

For several years, the city has been looking into allowing various types of accessory units along the Green Line, within a half-mile of University Avenue between ­Emerald Street and Marion Street — essentially from the city’s western edge to the Capitol area.

Some community councils have expressed interest in allowing the units citywide or beyond the proposed area, Radel said. Whether to take a broader look at the issue is up to the City Council, she said.

Council Member Dai Thao, whose ward includes much of the area that would be affected, said he needs more time to analyze the issue and has not decided whether he will support the ordinance, which was given a second reading this week.

The City Council will hold a public hearing on the accessory dwelling plan Wednesday.

Neighborhood concerns

Accessory units have been particularly controversial in the St. Anthony Park neighborhood near the University of Minnesota’s St. Paul campus.

Some residents feared the units would change the ­neighborhood’s character, said Phil Carlson, who led a task force that looked into the issue. The group was evenly split between supporters and opponents, he said.

Linda Foster, who lives in St. Anthony Park, opposed the units. At a Planning Commission hearing on the topic, she said accessory units can be “the kiss of death for a neighborhood.”

The first generation of people to own the units may keep it up, but after that the accessory dwellings can deteriorate, she said.

People were also concerned about the addition of renters and loss of on-street parking space, said Suyapa Miranda, executive director of the St. Anthony Park Community Council.

“It’s an affluent neighborhood,” she said.

“And then really thinking about what the neighborhood looks like, and does it fit with the neighborhood and what the current style is? And a lot of people’s understanding is no.”

Despite concerns, the community council voted in support of the proposed city ordinance allowing accessory units.

The units could help reduce per capita energy use, make some large homes more useful and provide housing needed for seniors, Suyapa wrote in a letter to the City Council.

She said the units would offer lower-cost housing to people who otherwise would not be able to afford to live in the neighborhood.