With San Francisco housing costs at an all-time high — and land at a premium — Oakland Mayor Libby Schaaf tossed out an idea that she admitted might sound a bit crazy: What if San Francisco housing developers could fulfill their affordable housing requirements by building some of that housing in Oakland?

Schaaf shared her idea at a meeting with Chronicle editors last week, explaining that it’s an idea she hasn’t talked to San Francisco officials about yet. It came in response to a question about what she believes she can do to deal with the region’s housing shortage.

“We don’t have a concrete plan, but what we do have is recognition of the problem,” said Tomiquia Moss, Schaaf’s chief of staff.

“What has been vetted, what we do know, is that no one city can address the regional housing crisis by itself,” Moss said. “San Francisco and Oakland can’t solve these problems on their own because jobs, transportation and housing are all components that people think about when deciding on a place to live.”

The idea is for San Francisco residents who qualify for below-market-rate housing to live in affordable units that would be built in Oakland.

Finding regional solutions to the housing problem is an idea that has generated discussions between planners and sparked interest from the Association of Bay Area Governments, an agency that advocates for regional solutions to a wide range of public services and needs.

The loss of redevelopment funding, environmental constraints and regulatory requirements have slowed the affordable housing process, Moss said.

“The large cities are trying to be thoughtful about regional collaboration, and it’s not just San Jose, San Francisco and Oakland,” she said.

“We need to work together to come up with creative ideas to address challenges all cities are facing.”

Schaaf’s idea also lines up pretty closely with the long-term Sustainable Communities Strategy regional planning law passed in 2008 and being carried out by the Metropolitan Transportation Commission and ABAG. The law calls for the state’s 18 metropolitan areas to accommodate future population growth while at the same time reducing vehicular carbon emissions.

In the Bay Area, it means that the nine counties must come up with a working plan to provide housing for all income levels and to promote use of public transportation systems to reduce car use, emissions and urban sprawl.

The foundation for the partnership is already being prepped in Oakland, where the Bay Area Council sponsored a tour of specific sites identified for development by Oakland city officials. Representatives from more than 50 development firms took the tour, city officials said.

Christine Falvey, a spokeswoman for San Francisco Mayor Ed Lee, said Lee is committed to building 30,000 housing units in San Francisco in the the next five years and has set his sights on making one-third of them affordable.

He is also generally willing to explore regional housing partnerships, Falvey said.

Unfortunately, affordable in San Francisco still translates into about $500,000 for a two- or three-bedroom house in Hunters Point, the city’s old shipyard district.

Miriam Chion, ABAG’s director of planning and research, has met with planners from both cities who are brainstorming on ways to collaborate on regional housing and transportation challenges.

“I think Oakland and San Francisco have taken the current economic growth and development pressure as an opportunity to collaborate and address some of the pressing housing needs and needs for planning for regional job growth,” Chion said.

“We’re under huge pressure to provide housing for a growing population and working families, and if Oakland can build affordable housing for this population, it would be a huge gain for the cities and the region as a whole.”

Chip Johnson is a San Francisco Chronicle columnist. His column runs on Tuesday and Friday. E-mail: chjohnson@sfchronicle.com Twitter: @chjohnson