San Francisco's building code got downsized Tuesday with the Board of Supervisor's approval of a pilot program that will build efficiency units, or apartments with reduced square footage requirements.

The board, in a 10-1 vote at this afternoon's board meeting, approved the ordinance that will change the definition of an efficiency dwelling unit to include units that are as small as 220 square feet, including the bathroom and closets.

Part of the legislation is a program that caps the construction of these mini-apartments, at yet to be determined locations, to 375 units.

The Planning Commission is then required to provide an analysis of the efficacy of the smaller living style before the program could be expanded and more such units can be built.

The legislation, introduced by Supervisor Scott Wiener, was touted as a way to address the housing crisis in San Francisco where one bedroom apartments and studios can run up to $3,000 per month in rent.

"This could be the difference between staying in the neighborhood or leaving," Wiener said.

He acknowledged that with rising rents throughout the city, many residents already live in close quarters.

"We already have micro-units in San Francisco -- it's called roommates," Wiener said.

Wiener said the small apartments will offer people an option to live on their own at more affordable prices, with the figure of about $1,500 per month rent discussed as an average rate.

The sole dissenting vote came from John Avalos, who said the micro-units don't seem like the proper solution to alleviate the city's housing problems, especially for working class families getting priced out of their neighborhoods.

"This overall does not make sense for the San Francisco that I know," Avalos said.

Avalos cited his own situation as part of a family of four living in the southern part of the city in District 11 in a 950-square-foot home, maxing out all the available space and unrealistically able to move into an efficiency unit.