Zoning Systems
May 15, 2014

I am going to start a series of blog posts on zoning and land use regulation. As my first blog post in the series, I am going to introduce zoning and the different types of zoning systems that are in place.

Zoning refers to any system where restrictions and laws vary within in the same jurisdiction based on area, or zone. The meaining of the verb 'zone' means to 'divide into or assign to zones' (Google). Any set of laws or regulations which vary based on property, blocks, or some other divison of area could be considered zoning.

There are multiple zoning systems in use, I will describe the three major types I have encountered.

Euclidean Zoning

Euclidean zoning is the most popular form of zoning in the United States and Australia - with a few exceptions. Euclidean zoning is also known as used-based zoning, single use zoning, or exclusionary zoning, and is known for its emphasis on how a property may be used rather than its form.

Euclidean zoning works by assigning properties a zone, and each zone corresponds to a use. In the simplest implementation of Euclidean zoning a zone may be reserved for residential, commercial, or industrial use. A more advanced Euclidean zoning will further divide these zones - residential may be divided into single family residential, duplexes, townhomes, and apartments based on how many families or people can live there. Commercial may be divided into small retail and big box retail based on how much floor space the shops can build and how many businesses may occupy the site. Industrial may be divided into offices and factories. There are often a dozen zones or more.

Let's look at the zoning map for Conway, Arkansas. Each colour on the map refers to a different zone. Except for Northeast Old Conway, Conway largely has a single-use Euclidean zoning system. You can see that this map is very colourful;

They broke down - on a block my block basis - exactly where the people can live, where the shops are, where the offices are. It is called exclusionary zoning because it has been designed, from the beginning, to seperate uses (by excluding all but the specified use from occupying that zone).

A quick note here - as a traditional urbanist - I have never been to a city that has a purely single-use zoning system that has felt exciting and energetic.

Maximum-Use Zoning

Euclidean zoning does not work very well for urban areas, because many urban areas were established before Euclidean zoning came into effect. These areas had properties that were 'mixed-use' (people lived above their shop, or the department store had a factory upstairs, for example) and could not be described by a single use as in Euclidean zoning, so many urban areas adopted a system where they could assign a maximum use rather than a specific use to zones.

Maximum-use zoning, also known as inclusive zoning, is distinguished by Euclidean zoning, in that it still regulates land use, but in a pure maximum-use zoning system, each level of land use also allows all of the former land uses. For example, a residential zone may only allow residential uses, however a commercial zone will allow both residential and commercial uses. An industrial zone will allow residential, commercial, and industrial uses.

This table from Urban Kchoze visualizes the maximum-use zoning system in Japan;

The theory is that we cannot micromanage demand for each use (how do we know we need exactly 140 houses and 10 shops in an area?), so by setting a maximum use, the free market can balance the land use itself up to the maximum use, while keeping underdesirable uses (such as heavy industry in a residential area) out.

This is generally acceptable because while a homeowner may not want a factory, office, or shop to open up next door, a homeowner may choose to live next to a factory, office, or shop. Sometimes this is desirable (employees may be interested in cheap housing near their workplace, business owners may be interested in living next to their business, etc.)

In the United States and Australia, a pure maximum-use zoning system is rare, and is often mixed with Euclidean zoning creating a hybrid zoning system where they exist.

Here is the zoning map for downtown New Orleans;

The pink zones in the middle are the CBD zones. CBD-1 is defined as "any use permitted in the RM-4 Multiple-Family Residential District" but also allows many commercial uses. CBD-1 is then used as the base zone for describing the other CBD zones. For example, CBD-2 is defined as "any permitted use authorized in the CBD-1 District" and uses such as casinos and guest houses. CBD-4 is defined as "any use permitted in the CBD-1 District, except guidance services" but including low-intensity commercial such as bakeries, bicycle shops, and laundromats.

The cyan blue zones above are the VC zones that cover the French Quarter. They similarly include and extend other zones.

While this is not a pure maximum-use zoning system, it shares many of the same traits, as each zone includes the uses of a previous zone, rather than being an exclusive use within itself.

Form-Based Codes

A form-based code is a zoning system that regulates the form rather than potential uses of the property. One of the arguments I often hear for Euclidean zoning is to "perserve the character" of an area (on this topic - I find it amusing how people want to "perserve the character" of suburbia as if it is something unique - even though car-oriented surburbia pretty much looks the same from coast to coast) however, purely regulating land use does nothing to prevent ugly forms that can break the character. Most Euclidean and maximum-use zoning systems add regulations such as floor:area ratios, setbacks, and height restrictions to try to control the physical form of what can be built.

Form-based codes take this one step further by only regulating the form and not land uses. SmartCode is a popular form-based code template which defines 'transect' zones;

There is no mention of land-use, only the physical form.

A form-based code does not only have to regulate the visual physical form, but can also regulate noise, stench, and any thing else which defines the way in which the property interfaces with its external environment.

Wikipedia has examples of communities that have implemented some form of a form-based code.

Conclusion

I have introduced three major types of zoning systems that are in use. If you know of any others - please contact me and I will add them. Many communities have hybrid zoning systems that combine elements of all of them (form, maximum-use, and exclusive use) - New Orleans was the perfect example. There are many examples of Euclidean zoning systems that have had a 'mixed use' zone patched on top of it.

For my next blog post, I am going to talk about how zoning can distort market demand.


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anonymouse • 05.16.2014 • 15:58 PM (MDT)
The typical zoning code has both Euclidean and form-based elements though. I've read a few of them lately, and the general structure defines a number of zones and permitted uses therein, but also defines very specific dimensional requirements on lots in those zones and houses in those lots. They're not generally architectural standards, though, they just define a box that establishes the maximum limits of what can be built. And amusingly enough, when these suburban-derived codes applied to pre-existing cities, ostensibly to "protect the character of neighborhoods", the result is that most of the city does not actually conform, and complying with the code would involve tearing everything down, completely redrawing the lots, and rebuilding everything from scratch at a much lower density. Fun fact: in Somerville, MA, over 98% of the lots in the RA and RB zones (2- and 3- family residential, which make up the builk of the city) are noncompliant with at least one dimensional requirement of the code. There are about 20 lots (out of 11,000) that are compliant.