There are few municipal functions more basic than zoning and planning, the rules and process that dictate what can be built, where it can go, and how it should be done.

In Philadelphia, most agree, that system is badly broken. An ancient zoning code and fickle political forces make building here a risky proposition for any big developer. And the Planning Commission is so weak that even skyline-changing towers can be erected with little to no meaningful input from public planners.

But momentum is clearly building within City Hall for a top-to-bottom overhaul of Philadelphia's haphazard approach to zoning and planning.

A commission formed last year is rewriting the nearly half-century old zoning code. In January, Mayor Nutter swept away all but one of Mayor John F. Street's appointees to the city's three most critical zoning and planning boards and commissions. And this month, Andy Altman started work as Philadelphia's first deputy mayor for planning and economic development.

Even City Council - not usually regarded as a bastion of solid urban planning practices - is showing signs that it might be willing to change the system.

Last week, for instance, Council Members Bill Green and Brian J. O'Neill said they favored creating a design review board to pass judgment on the look and feel of big new developments. Similar entities are popping up across the country, as municipalities seek to exert greater control over the cityscape.

It would certainly be a big change for Philadelphia.

The only design review developers have been subject to in recent years is an informal mishmash of neighborhood input and hard-to-predict directives from the Zoning Board of Adjustment.

The city's planners - who are the actual experts - frequently are cut out entirely, or briefed only when a project has all the permits and zoning approvals it needs.

O'Neill wants to change that, and he wants to see the legislation within three weeks. But that's not going to happen.

"Everyone wants to do this quickly. We have to do it thoughtfully," said Altman, the new deputy mayor.

Altman said he and Nutter were strongly committed to asserting a major role for the city's professional planners in development review, but that he did not yet know whether a design review board was the way to do it.

"You're looking at a whole system of how planning's been done in the city," he said. "We shouldn't kid ourselves, it's a massive undertaking."

Which is to say that the Nutter administration believes it will take years, not weeks, to fix the planning mess.

The roots of the problem run deep. Planners and architects blame much of it on the zoning code, which was drafted in 1960. But they also say that city planning has suffered due to mayoral neglect and a weak local economy.

"Sometimes planning can seem like it is getting in the way of development in a city that for many years was starved for development," said the architect Alan Greenberger, who is the new vice chair of the Planning Commission.

As careful review of proposed developments was short-circuited in the name of economic progress, the city's planners lost clout. Even after Center City boomed, developers were not made to reckon with Philadelphia's professional planning staff.

Rather, the road to development approval ran straight through local civic associations, which have far more political influence than do urban design experts.

"Going to the Planning Commission was a formality; they were just not an integral part of the process," said the developer John Westrum, who is on the commission that is rewriting the city's zoning code. "You had to strike your deals with the community groups."

The deals typically involved some changes to a proposed design - more parking, for instance, or additional lighting. But some bargains also included community benefits that had nothing to do with the proposed development, such as new computers for a local recreation center.

"We devolved into a system of pure transactions. It's not what was intended, it's just what happened," Greenberger said.

In theory, once a new zoning code is in place, there will be less opportunity for deal-driven development. But even the most optimistic observers think it will take years to draft the new zoning code and map.

Indeed, the commission charged with the job is still interviewing consultants and looking for an executive director.

"There's a certain level of impatience. People are starting to understand we're in the very early stages," said Sam Sherman, who is president of the Building Industry Association of Philadelphia, an organization for residential developers.

Sherman cautioned against hastily setting up a design review board.

"I understand the intent, but it would be adding to the bureaucracy, it would be yet another commission that would have to stamp off before you come to market," Sherman said. Better in his mind to let the new zoning code do the work.

Some developers, however, would embrace a design review board if it led to a less helter-skelter building approval process.

"Anything that provides predictable results and a predictable process will encourage investment in the city of Philadelphia," Westrum said.

Just as important as the developers are the civic associations, which have grown increasingly savvy and powerful while filling the vacuum left by the weak Planning Commission.

Their leaders are unlikely to accept any new system - be it a reworked zoning code or a design review board - that diminishes their role significantly.

"A bunch of professional planners in a room are not going to have the sense of community that civic associations have," said Rob Stuart, president of the Logan Square Neighborhood Association.

Not that Stuart or other civic leaders want to cut planners out entirely. Indeed, Logan Square is creating a formal neighborhood development plan with the help of the Planning Commission, a model that Stuart likes.

"I think the answer is for the city to provide professional resources for planning and design to civics," he said.

Striking the right balance between civic participation and professional planning is just one of many challenges Altman faces.

He needs money. The Planning Commission is "severely underfunded and understaffed," in the judgment of Greg Heller, a planner at the Delaware Valley Regional Planning Commission. So far, however, the Nutter five-year financial plan doesn't include an extra dime for planning.

Altman also must navigate a difficult interim period before the zoning and planning changes are complete. Given Nutter's campaign promises, residents expect to see vigorous urban planning, but that won't be easy until the old system is scrapped.

"The answer is, there's no good immediate answer," said Heller, who completed a major study into Philadelphia's lack of design review in November. "We're really suffering now for not fixing our zoning earlier. We've been operating under a broken system for a long time."