When Kristin Hansen and her husband, Eric, were ready to start a family, they made plans for a 700-square-foot addition to their Noe Valley house. They expected they'd have to carefully follow planning codes, get architectural drawings, and speak to the neighbors.

What they didn't expect was a 2 1/2-year, $150,000 nightmare.

The Hansens fell into the city's residential rabbit hole - a process called "discretionary review."

In simplest terms, discretionary review means that neighbors can object to changes in their neighborhood if a project is deemed to be "exceptional and extraordinary" and get a hearing before the City Planning Commission - even if city planners have approved the project.

John Rahaim, the city's planning director, says this is the only large city in the United States to grant residents such wide-ranging power.

"The neighborhoods really believe they should have the right to go to the Planning Commission to object," he said. "We understand that. Sometimes DRs are filed for good reasons. But sometimes they are very frivolous."

While planning officials and others have advocated a higher standard for filing a discretionary review, the Board of Supervisors has been reluctant to diminish the power of persnickety neighbors who may just drive well-meaning residents to the suburbs.

Everyone has a horror story. There was a discretionary review filed by a neighbor against a new backyard deck because the neighbor feared the deck would lead to the use of a grill, and those fumes would waft over their house.

Architect Cassandra Mettling-Davis was an advocate of discretionary review until she was entangled in a contentious review that saw her client asking to move a backyard deck 6 feet farther away from the neighbor's property line. Mett-ling-Davis battled the review for three months, costing her client thousands of dollars. "The neighbor withdrew the DR half an hour before it went before the (Planning) Commission," Mett-ling-Davis said.

Gabriel Metcalf, executive director of the nonprofit San Francisco Planning and Urban Research Association, says rarely are the issues "exceptional or extraordinary."

"The current process does not work for anyone," Metcalf said. "We want the Planning Commission to focus on big planning issues, not micro-design issues."

The Board of Supervisors' budget analyst advocated for reform in 2002, and Metcalf's SPUR agreed in 2007. The City Planning Department created a website promoting discretionary review reform, and last year the Board of Supervisors' Land Use and Economic Development Committee considered an ordinance that would have raised the bar for what is "exceptional and extraordinary."

But in March, the issue was tabled for a year. Now is the time to for the Board of Supervisors to set a higher standard for discretionary reviews. They will face a tough fight because the vast majority of DRs are filed in affluent areas such as the Castro, Noe Valley and Upper Haight, which have well-organized neighborhood groups.

But not every San Franciscan has the time or money to deal with these complaints. Hansen and her husband ended up going to the Planning Commission, the board of appeals, and finally a two-hour session of the Board of Supervisors. They won, but only after hiring a historical expert and a political consultant, as well as attending hours of meetings.

"Frankly, the process was very difficult for the objecting side too," she said. "This creates lingering feelings in the neighborhood."

Today Hansen says they are resigned to the idea they will never get the money back out of the house. But they now have enough room for their two young children. And they are living in San Francisco.

But the next time someone asks why families don't stay in the city, one reason can be summed up in two words: discretionary review.