A plan for basement apartments passed 7-2 at Monday’s meeting of the City Council, despite councillors having a week to think it over since passing it 6-2 and a new round of comments from residents who are opposed.

The Basement Housing Overlay District — usually referred to as the Chestnut Hill Realty petition after the company that asked for it — first affects 13 buildings along Massachusetts Avenue between Porter and Harvard squares, all with at least 30 existing apartments including a basement unit and all built before 1930. If the studio and one-bedroom apartments are considered a success, the zoning could be expanded citywide and affect another dozen buildings.

After the vote a week ago, councillor Craig Kelley submitted a request for reconsideration. But the seven days he and vice mayor Henrietta Davis had to persuade other councillors to vote no were fruitless, and Sam Seidel, who was missing from the first vote, joined the majority to vote in favor.

Mayor David Maher and councillors Marjorie Decker and Ken Reeves were urged Monday not to vote on any matter involving Chestnut Hill Realty by recent council candidate Gary Mello, because company-related campaign contributions gave their votes “the appearance of impropriety.” The three officials declined Mello’s suggestion without comment.

Aside from Mello’s concerns about money appearing to sway votes, there were concerns about parking from fellow candidate Tom Stohlman (who felt allowing basement units to go in without matching parking spots “should not be passed without some corresponding benefit to everybody else in that zone”) and about the quality of basement apartments in general. “I looked at a lot of basement apartments when I was [first] looking to live in the city several years ago, and all of those were all in terrible condition. I would have been very sad if I had to live there,” resident Dara Glass said. “They don’t offer a good quality of living.”

Backers of the plan, including former mayor Sheila Russell and Chestnut Hill Realty’s director of development, Mark Levin, painted a different picture of what Levin called “moderately priced housing … affordable to a wide range of renters,” mentioning large windows and high ceilings to go along with mandated separate water and sewage lines and case-by-case approval from city engineers keen on keeping renters from being flooded.

The zoning will create a few units of affordable housing; most basement apartments will be market-rate but, according to Chestnut Hill Realty’s Matthew Zuker, between 15 percent and 20 percent cheaper than above-ground apartments in the same buildings.

Heather Hoffman, a real estate attorney and co-president of the Association of Cambridge Neighborhoods, had data for Chestnut Hill Realty’s buildings in the Basement Housing Overlay District, including the John Harvard Apartments at 1-3 Langdon St., which she said the company bought for $250,000 in 1976 and is now assessed at $4.8 million; the Wendell Terrace Apartments at 19-21 Wendell St., bought for $235,000 in 1976 and now assessed at $4.9 million; and the Chauncy Court Apartments at 18-26 Chauncy St., bought for $2.6 million in 1986 and now assessed at $12.7 million. Calculating 80 percent of the value of studio and one-bedroom housing in those buildings, Hoffman found a basement apartment could get as low as $1,412 at the John Harvard Apartments and $1,124 at the other sites.

Each of the mortgages have been refinanced recently, to  $6.2 million from $4.3 million at the John Harvard Apartments, to $6.4 million from $4.5 million at Wendell Terrace and to $17.7 million from $11.3 million at Chauncy Court.

“That’s nearly $10 million that was taken out of these buildings two months ago. It is reasonable  to conclude there is a lot of value in them, and I suggest strongly that they can in fact afford to put in affordable apartments,” Hoffman said of the Realty.

Her association proposed an amendment last week to the zoning to make affordable housing out of all new basement apartments or an equal number of them, but it failed 6-2.