What makes Philadelphia's new zoning code such a landmark policy is that it embraces the modern view of cities first articulated by such urbanists as Jane Jacobs and William H. Whyte. They understood that cities couldn't survive with fortified streets and blank ground floors. In the spirit of that movement, the code took the bold step of banning a particular local scourge: garage-fronted rowhouses.

Apparently, the Zoning Board of Adjustment never got the memo.

The new rules went into effect eight months ago, and yet the board continues to conduct business as usual, handing out variances that allow rowhouse developers to install garages where the living rooms are supposed to be.

Last week, it was a pair of houses at 19th and Catharine Streets. Those variances came just weeks after five garage-fronted rowhouses were approved nearby at 19th and League. Across town, in Bella Vista, two more such houses on Eighth Street recently secured the board's blessing.

Because no city agency tracks the board's decisions, it's impossible to know precisely how many of these Frankenhouses have been approved since the code debuted. I learned about the nine I mentioned from neighborhood groups. The city's chief planner, Gary Jastrzab, told me he had identified eight others, bringing the known variances to 17. We should assume there are more.

Every one of these faceless garage doors is like a dagger in the body of the city. Because they occupy so much facade space on the ground floor, there is usually no room for a window and the sense of habitation that would convey. Garages make the street less friendly, less safe, less comfortable. After all the work by planners to stop their proliferation, the board's actions are "demoralizing," said Lawrence Weintraub, who co-chairs Bella Vista Town Watch's zoning committee. "I'm concerned that this makes the new zoning code look like a joke."

The nine variances in the Graduate Hospital and Bella Vista sections are especially disturbing because they were opposed by a broad civic lineup: the Planning Commission, the neighborhood association, and the district councilman.

By disregarding their voices - not to mention the City Council-approved zoning code - the board is effectively setting its own planning policy. That's not what a zoning board is supposed to do. And it's certainly not the way a democracy is supposed to work.

High-handed decisions are hardly a new thing at the zoning board. Mayor Nutter campaigned in 2007 on a pledge to rein in the out-of-control board. He made good on that promise, in part, by supporting the citizen-led effort to update the '60s-era zoning code, a process that took four years of grueling negotiations. The result is a civic compromise that deserves to be respected.

So why won't the zoning board behave? The garage variances expose a fundamental weakness in the structure of Philadelphia's government embedded in its 1951 Home Rule Charter. The Planning Commission can only recommend what should be built in the city; it's the zoning board that has the power to issue the necessary permits. So, even though the Planning Commission oversaw every step of the code rewrite, it can't force the zoning board to execute its policies.

The mayor can, through his appointments to the zoning board. Yet board members often seem to develop their own agendas. That was true of the strong-willed chair, Lynette Brown-Sow, who left last week after Nutter named her to run the Philadelphia Housing Authority board.

Jastrzab told me he hopes Brown-Sow's replacement, Julia Chapman, will be more sympathetic to the Planning Commission's wishes. "It's very likely attitudes will change with Julia," who ran Nutter's Council office, he said. But unless Nutter lays out his expectations in no uncertain terms, expect Chapman to revert to type.

Garage-fronted rowhouses have, of course, afflicted the city's streets for decades. But their numbers are growing as gentrification comes to once-blighted areas such as Graduate Hospital and Point Breeze, where there are large tracts of empty land for infill housing. You can already see blocks in Graduate Hospital deadened by lines of garages running end to end.

It may be hard to believe, but the city once required a garage in every new rowhouse. About a decade ago, policymakers began to understand the harm they caused Philadelphia's charming rowhouse streets.

It is not an easy issue. Many developers are convinced they won't be able to sell a new house without a garage. Of course, many buyers want garages, too. Because of the configuration of Philadelphia blocks, it is often impossible to tuck garages in the back of the house, where they would be less obtrusive.

It is worth remembering that most older rowhouses have no garages. Car owners park on the street. Yet every time a developer builds a garage-fronted rowhouse, the city loses an on-street parking space. A scarce, public commodity is transferred to the private realm.

By approving garage-fronted rowhouses, the zoning board sends a message that the Nutter administration wants to encourage car use. It undermines his transportation staff, who are working hard to encourage SEPTA ridership. The variances go against Nutter's stated promise to make Philadelphia the greenest city in the nation.

Along with property-tax reform, the new zoning code promises to be Nutter's greatest legacy - unless he continues to allow the zoning board to sabotage it.