Everybody in California is talking about form-based codes these days. Cities throughout the state are in the process of adopting these codes. The wave is growing so fast that form-based codes appear to represent a revolution in the making.

But nobody seems to know what form-based codes are.

That, at least, is the impression we get here at CP&DR. Over the past year, no single question has come up more frequently than: What in the world is a form-based code?

The answer lies in the century-long battle for power in land-use planning between designers and lawyers. Since the dawn of modern planning during the 1890s, designers have focused on the shape and form of urban growth, especially in the public realm – the design of streetscapes and public squares, the creation of great places as a backdrop for a city. Lawyers have focused on the do’s-and-don’ts of regulating private development at the parcel level, which emerged largely out of nuisance law. The basic idea was to identify which “uses” are incompatible and separate them. (This battle is described in detail in Chapter 3 of my book co-written with CP&DR Editor Paul Shigley, Guide to California Planning.)

The traditional zoning code, with its long list of use districts and uses that are permitted or banned, represents a victory of lawyers over designers. The “form-based code” is an attempt by design-oriented planners to swing the balance back the other way.

The basic idea of a form-based code is pretty simple: It places more emphasis on the design and form of buildings than a traditional zoning code does, and less emphasis on uses inside the buildings. This kind of approach makes sense today in a lot of places in California, where the main task of planning involves managing the transition from suburban to city-style development.

The New Urbanist architect Victor Dover has summarized it simply by saying that a form-based code is a “design-oriented code.” This conveys the general idea – maybe better than “form-based code” — but it’s not quite specific enough, which is why the New Urbanists prefer the dense term “form-based.” It’s not really about the typical details of architectural design, such as façade treatments, color schemes, and architectural styles. It’s about the guts of urban design – the form and massing of buildings, the width and design of streets, and the physical relationship between the buildings and the streetscape. A form-based code usually has a lot of illustrations so that developers and architects can see what the code-writers had in mind rather than imagine it for themselves after reading the text.

This is not to say that a form-based code completely abandons traditional zoning concerns, such as use districts, units per acre, and parking ratios. Many form-based codes do contain such standards. But these standards are often more permissive – allowing greater flexibility – while the code focuses in great detail on urban design standards.

New Urbanists often argue that the use-based code makes the creation of great places “illegal,” and a form-based code simply represents a return to the type of planning that characterized great cities for thousands of years before the invention of the car and modern zoning. It might be fairer to say, however, that the form-based code simply represents an attempt to accommodate a more urban situation in California.

New Urbanist rhetoric aside, a traditional zoning code does force the creation of a suburban environment, with its setback, parking, and landscape standards. And it’s usually silent on the question of what buildings are actually shaped like. But as California becomes more urban, and infill development continues to increase in importance, the commonly held idea that compatibility problems can be solved by more space between buildings becomes less realistic. In that sense, a more design-oriented approach such as the one used by form-based codes is probably appropriate – because that is how compatibility problems will be solved.

Perhaps the best way to explain a form-based code is simply to describe one that is already in place. One of the first form-based codes adopted in California was the “smart code” adopted by the City of Petaluma for the Central Petaluma specific plan in 2003. This code was adapted from the copyrighted “SmartCode” created by Duany Plater-Zyberk of Miami.

The Petaluma code is not particularly short. In fact, it is 54 pages long. Nor does it look much different from a typical code, at least at first. It has a zoning map and a chart showing a list of uses in each zone. It also has parking standards. But these characteristics do not function quite like they do in a standard code. And the Petaluma code has other things in it that a typical code does not.

The Petaluma zoning map has different districts, but those districts are not typical of a zoning map. Some are tied to the New Urbanist idea of a “transect.” The transect divides the developed world into six zones – T-1 through T-6 – that range from extremely rural to extremely urban. The idea is that compatibility is not simply a matter of use; rather, neighborhoods should have compatible urban, suburban or rural fabric.

There is one chart in the Petaluma code that calibrates the traditional land uses (i.e. general retail, 10,000 square feet or less) to the zones on the zoning map and specifies which ones need conditional use permits and which ones do not. There is another chart that specifies densities, parking ratios, setbacks, and height limits – though all of these standards are most definitely not suburban in scale. Setbacks have both minimums and maximums, for example, and all residential development requires only one parking space per unit.

The Petaluma code differs from traditional codes in several other ways. For one thing, it devotes many pages to creating street standards. It also incorporates an alternative parking mechanism, specifying how developers may avoid on-site parking requirements either through participation in a parking district or by securing off-site parking. This alternative approach to parking is an increasingly common characteristic of form-based codes. In the form-based code world, parking, like so many other things, is a problem to be solved at the level of the district or neighborhood, not on each individual parcel.

Unlike many form-based codes, the Petaluma code does not contain pages and pages of illustrated building types – a kind of “pattern book” for urban development. This is good and bad. On the one hand, form-based codes are supposed to focus on form and massing of buildings, so pictures help clarify the goal. On the other hand, a picture-laden form-based code can – implicitly or explicitly – impose a particular architectural style. (This appears to be O.K. with most New Urbanists, who like traditional architecture and despise modernism; but it is clearly not O.K. with modernist architects, whose buildings can sometimes fit into a New Urbanist context.)

Most important, what’s missing from the Petaluma form-based code are the dozens of use districts, each with a laundry list of what uses are permitted and what uses are prohibited. A few outright prohibitions are contained in the Petaluma code, such as adult businesses in live-work spaces. By and large, however, most uses are permitted in most districts, though many are subject to a conditional use permit.

Obviously, some use parameters must be wrapped around a form-based code. Most industrial uses would likely be banned from mixed-use areas where retail, office, and residential uses are permitted with great flexibility. And it is pretty clear that form-based codes will not work unless they are accompanied by neighborhood- or district-level plans for parking and other common needs. But in California’s increasingly urban context, focusing on the form of development — as opposed to the use — makes a lot of sense.