San Francisco supervisors unanimously approved a nine-story building to house low-income seniors in the Mission District on Tuesday, rejecting an appeal by some neighborhood residents who criticized the project as being too tall, for lacking any parking spaces, and being out of character with the neighborhood.

The project at 1296 Shotwell St. is the first to take advantage of legislation by Supervisor Katy Tang passed last year that allows 100 percent affordable housing projects in San Francisco to have three extra stories.

About a dozen people came to the board hearing to express opposition. Mission resident Erica Levin criticized the proposed building as “uninspired, bunker-like, and not in keeping with the architecture of the area.”

Another Mission resident, Albert Pastine, said “the planners of this proposal have some cockeyed notion that if there are no parking spaces these people would choose healthy options” like biking and walking.

But the opponents were dwarfed by dozens of people who showed up to speak in support of the project, which is being developed by the Mission Economic Development Agency and the Chinatown Community Development Center, and its approval by the supervisors never seemed much in doubt.

Supervisor Hillary Ronen, who represents the Mission, said parking would not be an issue because seniors are less likely to drive, the project is in a transit-rich area, and the developer would offer shuttle service for residents.

“We need to build taller and denser when it’s more affordable housing in any appropriate spot in San Francisco,” Ronen said.

Charles Minster, a Mission resident, said he constantly worries that his landlord will throw him and his wife out of their rent-controlled apartment. He said there needs to be more housing for seniors like him.

“We have to change. If this city is going to remain a vibrant and growing city, it is going to have to build up,” Minster said.

Despite the supervisors’ unanimous support for the project, the law that allowed it to gain three extra stories was controversial. When the bill came before the board last year, Supervisor Aaron Peskin pushed a counterproposal that would have subjected those projects to a more rigorous and time-consuming approval process.

One of the next debates before the board will center on whether to allow developments that are not 100 percent affordable, but provide a certain threshold of low-income housing, to exceed zoning limits and become taller and denser.

Emily Green is a San Francisco Chronicle staff writer. Email: egreen@sfchronicle.com Twitter: @emilytgreen