A UC Berkeley study points to in-law units as a way to deal with the expected population growth.
Karen Chapple's backyard cottage is small -- around 425 square feet -- and she sees it as an example of an opportunity to house a population that will grow by two million in the next 25 years.
"Our study found that we can actually meet much of the affordable living needs through these units," Chapple said.
Chapple is a city and regional planning professor at UC Berkeley and is the author of the U.C. study that concludes that in-laws in five east bay cities make sense.
"Cities have not made it easy," said Chapple. "One in 5 homeowners can actually build these on their lots."
It's about the regulations in each city. Chapple says it's time to overhaul those regulations to make it easier for people to build on their own property.
"It's harder to get permission than to actually do the building," said architect Lennon Hamilton.
Hamilton might design some new in-laws, but is uncertain as to whether he wants them in his neighborhood.
"I think it's a good idea to have in-laws just in general," Hamilton said.
The study calls for building in-laws near BART stations in North Berkeley, El Cerrito, Albany, Richmond and Oakland with an emphasis on alternative transportation including bicycles and city car share so residents won't impact neighborhood parking.
There are those opposed to increasing density in their neighborhood, but Chapple says it could have an economic impact -- first for construction jobs, then with increased taxes and spending by new residents.
"It's something that can be done without a lot of government resources behind it," said Paul Fassinger with the Association of Bay Area Government. "It's something individuals can choose to do for themselves."
Fassinger sees it as a solution to future housing projects.
Hearings are expected in each city within a year over easing regulations.