# A Primer on Zoning Codes: The Basics

Zoning is a complex and arcane topic, even for those who interact with it regularly. In spite of this, zoning is all around us, in nearly every city, village, or town in the United States. There have been many good posts here at streets.mn discussing the merits and implications of zoning, but they often assume a certain level of knowledge. It would take many posts to fully explain zoning and all its intricacies, but I’d like to start at the very beginning.

### What is zoning?

When we talk about zoning in Minneapolis, or St Paul, or the rest of Twin Cities, or even most of the rest of the country, what we’re really talking about is Euclidean zoning, sometimes also known as single-use zoning or use-based zoning. Those with some knowledge of geometry may think, as I once did, that this name has something to do with the Greek mathematician Euclid, the “father of geometry.” It actually references the village of Euclid, Ohio, one half of the Euclid vs Ambler US Supreme Court case that opened the floodgates for use-based zoning in the United States. The core of Euclidean zoning is the segregation of uses. Residential districts should be segregated from Commercial districts from Industrial districts. One of the common examples of what this type of zoning does is preventing a dirty factory from being built next door to your home.

There are other types of zoning, the one most frequently brought up is a form-based code. An explanation of a form-based code deserves its own post, but generally a form-based code concerns itself with the forms the buildings take rather than their use. In a form-based code, a two story 2000 sq ft house is treated the same as an identically sized apartment building with four 500 sq ft units.

Modern zoning codes go far beyond a simple segregation of uses. They dictate how large the lot must be, how tall the building can be, how big the building can be (which is actually separate from how tall it is!), how and where the building sits on the lot, how much parking needs to be provided, and a variety of other miscellaneous things. The most important part of all of these is that zoning codes, in general, prescribe a ceiling, or maximum, on intensity of use. They will sometimes, but not usually, prescribe a floor, or minimum, on intensity of use. These floors, if they do exist, are generally much lower than the ceilings. These floors and ceiling are created through various maximums and minimums set forth in the code. A height limit in the zoning code, for example, sets a maximum height for a building. Regulations about the size and placement of a building generally set a maximum on the size of the building, but occasionally they will instead set a minimum for the size of the building, or sometimes even both a maximum and a minimum. Parking is usually a minimum. You must provide a minimum number of parking spots based on various criteria, though in some places, like downtown Minneapolis, there is instead a parking maximum.

### How do we talk about zoning?

Within a category of zoning, such as Residential, there are various levels of intensity, or restrictiveness. Minneapolis, for example, goes from R1, the least intense and most restrictive, to R6, the most intense and least restrictive. This convention seems apparent for zoning in other cities , that higher numbers are more intense and less restrictive than lower numbers. The first letter(s) of a zoning designation describes what general type it is, R, C, I, OR, or B in Minneapolis’ Zoning Code, followed by a number; the higher the number, generally the more intense the land use. St. Paul does it slightly differently. While they have Residential districts that all start with an R, they’ve used additional letters before the numbers.  St. Paul districts, in general order from least intense to most intense, are: RL, R1, R2, R3, R4, RT1, RT2, RM1, RM2, and finally RM3. Sometimes there’s another letter after the number, like R2B or C3A. This can mean a variety of things, depending on the specifics of the code. Of course not all zoning codes use higher numbers to denote higher zoning. Portland does just the opposite. R20 is one of the lowest intensity residential zones, allowing only one dwelling unit per 20,000 sq ft of lot area, or a bit under a half acre. R1 is one of their highest intensity residential zones, allowing up to one dwelling unit per 1,000 sq ft of lot area.

When we talk about “upzoning” or “downzoning”, we’re talking about moving a parcel of land up or down on this scale. A parcel of land in Minneapolis with R1 zoning carries more restrictions than if it were zoned R3 or R6. A St. Paul lot zoned R4 is zoned “higher” than another lot zoned R2. Changing the zoning of a lot or group of lots is called rezoning. When a Minneapolis lot is rezoned from R6 to R2B, that is a down-zoning. Going from C1 to C2 in Minneapolis would be an upzoning.

Finally, there’s another type of zoning district, referred to as an Overlay district. An overlay district does not replace a primary zoning district, but merely augments it with additional restrictions or guidelines. In Minneapolis for example, drive-thrus are allowed in the C2 commercial district. However, if a lot zoned C2 is also within a Pedestrian Overlay District, a drive thru is not allowed, as the Pedestrian Overlay District does not allow drive thrus. Another common type of Overlay district is a historic district, which prescribes certain guidelines, further regulating building size and architectural design to match that of the historic district.

You may notice that St. Paul and Minneapolis both have zones named R1, R2, R3, and R4. This doesn’t mean Minneapolis’ R4 can be compared to St Paul’s R4, however. R1 in Minneapolis may have a minimum lot size of 5,000 square feet, while R1 in an outer-ring suburb would require a lot to be many times that size. Despite all the general similarities between zoning codes, there are always specific differences between them, making direct comparisons between any two cities difficult to impossible.

### Is there any other jargon I need to know about?

Of course there is! I’ve barely scratched the surface. But this is just an introduction, so we’re not going to go too much deeper. There are a few more terms you might hear. Earlier I mentioned the size of the building. This is commonly called bulk, and is measured by Floor Area Ratio, or FAR. The FAR is the ratio of the total area of all floors of a building to the area of the lot. A 1,000 sq ft single story home on a 4,000 sq ft lot has a FAR of .25 (1,000 sq ft/4,000 sq ft). A four story building, with each floor being 2000 sq ft, on a 4,000 sq ft lot, has an FAR of 2 (2,000 sq ft x 4/4,000 sq ft). Zoning codes often include both height limitations and FAR limitations.

Floor Area Ratio diagram, via City of Seattle

A much simpler concept is building setbacks, which dictate how far away the building must be from the edge of lot. These are usually discussed in terms of front yard setbacks, rear yard setbacks, or side yard setbacks. Buildings that are built right up to the edge of the lot, as can be found in many older commercial areas all over the Twin Cities, as well as small towns all over the state, have side yard setbacks of zero feet, which can be referred to as “zero lot line” buildings.

Setback diagram, via Arlington County

This primer covers the very basics of zoning, looking at the differences between zoning district designations, overlay districts, height and bulk regulations, FARs, and building setbacks. But this is just the beginning – tell us in the comments where this conversation should go next!