Just a geek who lives in Olympia, WA with my wife, son, and animals, writing fiction that he hopes will make the world a better place someday.
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How much did cutting the middle out of our housing stock cost Olympia in the last forty years?

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Or, Olympia's spreading tax-subsidized single-family neighborhoods. 

I've pointed to this chart oftentimes as an illustration of how we changed directions back in the 1980s.

I've recently been rethinking this graph, mostly due to new perspectives on a fairly old policy tool to encourage apartment construction in downtown Olympia. Dan Leahy has been writing in Works in Progress about the multi-family tax exemption and how the rest of us are subsidizing new construction downtown.

While the discussion around the multi-family exemption does not reveal anything new (someone pays taxes if someone else is exempt), it does give a new ax to grind to people who would rather stay the course with how Olympia has been developing in the last forty years. Car-dominated suburban developments get a pass, while any sort of development downtown that is not a parking lot is given a side-eye or actually challenged legally.

But, the discussion did open an opportunity to examine how exactly our spreading suburban development pattern has cost the city's bottom line.

As a background, I used the Thurston County Assessor's parcel data provided by Geodata. This dataset gave me locations and construction dates (important for that chart), but also lot sizes and total values.

Also, I wanted to point out that only in the broadest sense am I talking about "denser" housing. Leahy is mostly discussing downtown Olympia apartment buildings, while I'm discussing anything from a duplex to a quadplex. While we oftentimes conflate these when we discuss housing and zoning, I want to make sure we know I'm talking about different types of housing. 

Now, let's get to the data!

At some point in the early 1980s, the construction of duplex to quadplex sized homes became disconnected from population. I chose 1981 as my splitting point because it seemed to make sense to me.

Between 1960 and 1981 Olympia averaged 6.2 two to four-unit buildings per thousand of population increase.

After 1981, that rate fell to 1.23 units per thousand new residents. Building non-apartment/non-single family home dwellings went through the floor after the early 80s.

What happened in the early 1980s? Go back and see the policy changes we made to favor single-family homes and the hateful political ecosystem that created it.

And because we know how many people have either been born or moved here, we can calculate how many du/tri/quadplexes we lost because we changed the rules. If we built at the same rate we did before 1981, we would have built 723 more du/tri/quadplexes. We currently have 786.

That on its own is shocking. That means we outlawed between 1,500 and 3,000 living spaces since the early 80s. If we continued building duplexes, triplexes, and quadplexes in Olympia, we would have nearly doubled the number of these more affordable units.

But, let us not stop there, this is about the public subsidy, not affordable homes removed from the market by bad laws. Because we know how much single-family home properties are worth and how much du/tri/quadplexes are also worth, we can calculate roughly how much each type pays per acre.

It should surprise no one, but the more dense housing types subsidize single-family homes.

Du/tri/quadplexes cover just over 216 acres of Olympia and they are valued at an average of $1,159,413 per acre.

Single-family homes cover over 4,528 acres of the city and those are valued at an average of $1,035,155 per acre.

This is not taking into consideration the added value du/tri/quadplexes would have brought to single-family homes.

So, when you lay out what we lost (at least 1,446 affordable units) against their higher value, you can get an idea of what our historic single-family home favoring policies has cost our city.

Doing a back of the napkin calculation based on last year's levy rate, the lost taxes (not just to the city, but to everyone who collects property tax in the city) was $3 million per year.

To put this into perspective, in his post that I linked to above, Dan Leahy points out that across of all the multi-family exemption projects, the loss in total government revenue is $3.4 million over eight years.

What we lose per year because we made a decision forty years ago to favor single-family homes is the same amount we lose over eight years for encouraging more dense development. This calculus also ignores the higher tax receipts that an apartment building will produce as opposed to a parking lot once the exemption is over. And, also (obviously) that the tax exemption is temporary, while single-family zoning is a bit harder to budge.
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The One Weird Rule That Explains Urban Sprawl

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In 1994, Cesare Marchetti, an Italian physicist, described an idea that has come to be known as the Marchetti Constant. In general, he declared, people have always been willing to commute for about a half-hour, one way, from their homes each day.

This principle has profound implications for urban life. The value of land is governed by its accessibility—which is to say, by the reasonable speed of transport to reach it.

Even if there is a vast amount of land available in the country, that land has no value in an urban context, unless transportation makes it quickly accessible to the urban core. And that pattern has repeated itself, again and again, as new mobility modes have appeared. This means that the physical size of cities is a function of the speed of the transportation technologies that are available. And, as speed increases, cities can occupy more land, bringing down the price of land, and therefore of housing, in newly accessed territory.

Modern Atlanta may bear little resemblance to the cities of past millennia, but its current residents share something fundamental with urbanites of the distant past: The average one-way commute time in American metropolitan areas today is about 26 minutes. That figure varies from city to city, and from person to person: Some places have significant numbers of workers who enjoy or endure particularly short or long commutes; some people are willing to travel for much longer than 30 minutes. But the endurance of the Marchetti Constant has profound implications for urban life. It means that the average speed of our transportation technologies does more than anything to shape the physical structure of our cities.

To see how, let’s travel back in time by more than 2,000 years, and move towards the present. (This journey will take less than 30 minutes.)

The city on foot: 800 BC-1700 AD

Until the Industrial Revolution, there was pretty much only one way for most people on dry land to get around: on foot. With services concentrated in the center of cities, the radius of development from the heart of the city was limited to not much more than one mile—about the distance a person can walk in 30 minutes.

Rome: The boundaries of the ancient city were limited by transportation technology—Romans had little choice but to walk. (David Montgomery/CityLab)

Sure enough, most cities from the ancients to the Industrial Revolution did not grow much bigger than a two-mile diameter. Their core areas were often even smaller, though some of the poor lived in settlements outside the city gates. Ancient Rome packed as many as a million people into an area a little more than two miles in diameter. Medieval Paris stretched about two miles from the Bastille to the Louvre, Vienna’s Innere Stadt measures only one mile in diameter, and the historic City of London is nicknamed the “Square Mile” for a reason. Beijing’s walls enclosed an inner city about three miles in diameter; into the 20th century, that still made up most of the developed area.

So as these old cities grew, they became denser. The narrow warrens of surviving European medieval cities, like Florence, Prague, or a few parts of Paris untouched by Haussmann, give one a good idea of this process. The arrival of horse-drawn mass transportation—the first fixed-route buses were created by mathematician Blaise Pascal in Paris in 1662—didn’t change this pattern; hooves didn’t get people around much faster than feet did.

Paris: Even a millennium later, transportation was still moving at a walking pace, which limited the ability of the city to expand. (David Montgomery/CityLab)

For most residents, the cities of this era were awful places to live, with extreme crowding, dismal sanitation, and routine outbreaks of vicious disease. Tenement apartments may seem livable when occupied by a couple, with an air conditioner in the window; they weren’t so pleasant when occupied eight to a room. The idea of escaping the city to the bucolic countryside is therefore as old as the city itself. Aristocrats kept country estates and villas for thousands of years; Vesuvius buried some examples under its rain of ash.

But even for the wealthiest, long-distance travel was an uncomfortable exercise, involving days on a horse or in a carriage on a rutty road. When Louis XIV centralized the French nobility in Versailles, he could be sure that their visits to their domains would be infrequent, which served his goal of limiting their power.

For the aristocracy of the pre-industrial age, commuting from a rural estate to a job in the city wasn’t possible on a daily basis—but such people did not tend to have what modern people would consider to be normal jobs. By the 19th century, the mercantile elite could not afford to be too distant from their urban enterprises. Invention quickly allowed the privileged few an escape.

The city on rails: 1840s-1950s

In 1830, British civil engineer George Stephenson opened the world’s first steam-powered public railway between Manchester and Liverpool. Soon, railways focused as much on proto-commuters as they did on intercity travelers. The London and Greenwich railway opened in 1836, and new lines quickly began radiating out of central London. Cities across Europe and the United States soon followed.

London: The industrial revolution was the first time in human history that transportation was no longer limited to human and animal power. Railways enabled relatively affluent people to live in lower-density settlements on the urban fringe, or in towns outside the city, and take the train into work. (David Montgomery/CityLab)

Steam trains couldn’t stop very frequently, because of their slow acceleration, and they were comparatively expensive. But once in motion, they could move passengers at an unprecedented rate: 10 miles or more in a half-hour. Instead of gradually extending the city, they created little villages around their stations a couple miles apart—railroad suburbs. Because access to the city was expensive, they were limited to all but the very wealthy and those who served them. The upper middle class lived within walking distance of the station; the truly rich lived on estates a short coach ride away.

Today, many of these villages remain enclaves of affluence: The Main Line suburbs of Philadelphia, Scarsdale near New York, Brookline near Boston, the “Stockbroker Belt” west of London, and Saint-Germain-en-Laye near Paris are excellent examples. America’s railroad city, Chicago, spawned several of the most legendary railroad suburbs, such as Evanston, Oak Park, and Lake Forest.

But for the urban masses, a different mobility technology would be needed. The horse-drawn omnibuses (or horsecars, their successors on rails) would not cut it. Thousands of workhorses pulling hundreds of wagons around the city created a serious environmental hazard, as the piles of manure on the streets could be literally as high as the people walking past. The smell of 19th-century city was beyond description, and the public desire for a faster and less malodorous form of mass transportation was fervent.

The city of bicycles and streetcars: 1880s-1950s

The invention of bicycles and electric streetcars provided such an alternative. The “safety bicycle,” which began supplanting towering “high-wheelers” in 1885, allowed any reasonably physically fit person to travel considerably faster than on foot. The first electric streetcar system entered service in 1888 in Richmond, Virginia, and the technology spread at the speed of electricity.

In practice, streetcars and bicycles could cover about 4 miles in a half-hour—much slower than the steam railroads carrying executives to their semi-rural estates, but much quicker than the horsecar and the human pedestrian. Suddenly the city itself was no longer limited to a few square miles, and developable areas grew exponentially. A walking city 2 miles in diameter covered only a little over 3 square miles; a streetcar city 8 miles in diameter could cover 200 square miles. It was the first great mass-market suburban boom.

Chicago: The development of a comprehensive streetcar and elevated train network allowed Chicago to grow far beyond the pre-industrial limits of cities. Middle-class people could commute on rails and live farther from their workplaces. (David Montgomery/CityLab)

Cities raced to grant streetcar franchises to entrepreneurs, and the industry experienced a boom much like that of the internet in the 1990s. Within a few years, every American city had at least a modest trolley network. Bigger cities had a web of rails sprawling outward in all directions, producing the urban typology that defined the turn-of-the-century era: the streetcar suburb. The middle class was no longer confined to crowded tenements; new neighborhoods sprouted on cheap farmland. They often took the familiar form of a main street lined with shops, with small streets full of single-family homes and townhouses running off that central spine.

The slower spread of the streetcar in Europe, let alone the rest of the world, contributed to the comparatively compact prewar design of their cities. Even in European cities like Berlin that grew quickly in the late 19th century, most new buildings were walk-up apartments.

The city underground: 1900s-1950s

London was a major exception. The world’s largest city needed a faster means of transportation. The poor still clustered in extreme density and squalor near their places of employment in the city center and docks, but railroads, by then quite high-capacity and frequent, enabled the middle class to spread into an array of suburbs, making London a more low-rise and less-dense city than its European neighbors.

The problem was getting from the various London train terminals to jobs in London’s traditional business district and elsewhere in the central city. Unlike in the poorer areas to the east and south, building elevated viaducts through some of the world’s most valuable real estate was infeasible. Charles Pearson promoted an ingenious solution: go underneath.

The first London Underground line opened in 1863, using steam trains. The route was a sensation, but clouds of smoke made the system a bit impractical, as riders came out covered in black soot. The solution—electricity—helped create the Tube we know today.

In America, the comparatively new cities tended to develop on a grid of straight roads, which meant that trains could sometimes be elevated over top of the streets without unacceptable curves rather than buried underground, as in central London and most old European cities. El trains were an ugly solution, but they worked. Cities like Chicago, Boston, Philadelphia, and New York City covered their streets with steel skeletons, and trains were soon rumbling above. They carried the growth of New York, for example, up the island of Manhattan. If trolleys and streetcars had brought midtown within a reasonable commute, elevated trains enabled nearly the entire island to be developed. A web of els spread throughout Brooklyn, connected by the Brooklyn Bridge to Manhattan. The system predated the city’s subway by several decades.

Elevated trains and (later) subways meant that even the working class could live as far as eight miles from their places of work and still get there in a half-hour. They could afford it, too, because many of the systems had a cheap flat fare regardless of distance. The teeming blocks of tenements began to thin out: New homes could be built on land cheap enough for the working class to afford a decent apartment, though racism built into the market limited the avenues of escape for many immigrants and, especially, African Americans.

Those who did flee left more room for businesses, like the skyscrapers that emerged in Chicago around the turn of the century, and the department stores like Macy’s and Marshall Field’s that occupied the most prominent corners in every city. Along with attractions like palatial vaudeville and movie theaters, these urban features draw people from miles around, since people were no longer restricted to a close radius around their homes.

The combination of technologies created the form of cities before World War II. Dense downtowns had high-capacity rail transit radiating outward—subways and elevated trains in big cities, which produced apartment suburbs that were relatively high-density, but still much lower than the old tenement slums; and streetcar suburbs, with single-family homes and townhouses. Some of the richest people lived beyond, in small towns and on estates accessible to the central city by railroad.

But this order was not to last.

The city of the expressway: 1950s-present

Like many technologies, the car began as a toy for the rich, used to reach their country estates or to race around on tracks. As a means of basic transportation, it was severely limited by high cost and lack of paved roads. That started to change in the U.S. with the introduction of Ford’s Model T in 1908, which was mass produced at a price that was affordable to this country’s comparatively affluent middle class.

Atlanta: The ubiquity of the automobile and an enormous government investment in expressways allowed Atlanta to disperse homes and jobs over a large area. (David Montgomery/CityLab)

Still, car commuting was not much more convenient or fast than existing mass transit. Roads built for carriages, wagons, and pedestrians soon became severely overcrowded. Cities in the 1920s and 1930s spread a little bit more than they had when everyone relied on the streetcar, especially in places like Detroit and Los Angeles where roads were wide and auto ownership was highest, but the age of the automobile would await another technology—the expressway—and the huge infrastructure transformation that adapted the city to the car.

After World War II, two dominant urban planning ideas contended to shape the city of the future. Both sought to solve what was seen as the great urban problem: overcrowding. The first was the “towers in a park” model famously espoused by Swiss-French architect Le Corbusier, who envisioned replacing crowded old cities with huge skyscrapers surrounded by acres of greenery. This vision was implemented in various adaptations in the post-war new towns in Europe, like La Défense and Clichy-sous-Bois outside Paris, Thamesmead outside London, and Vällingby near Stockholm. In the United States, his designs found favor mostly in government projects, like the monumental Empire State Plaza in Albany, and especially in public housing.

The Swiss-French architect Le Corbusier tinkering with a model of his “Ville Radieuse” urban plan. (AP Photo)

For the most part, Americans took another path. Frank Lloyd Wright developed the idea of the Broadacre City in 1932. He believed that the individual mobility provided by the car had made the city obsolete and proposed dispersing the population onto one-acre plots of land. It was a Jeffersonian vision that appealed to the deep-rooted American suspicion of the city. In 1939, a more commercial version was presented at General Motors’ Futurama exhibit at the New York World’s Fair. Broad expressways carried people into the countryside, where they could live in houses on lots that allowed plenty of room for a yard.

It is rare that one finds a past vision of the future that came true so precisely—abetted by lavish government assistance to build highways and widen urban streets into automobile-oriented thoroughfares. After all, Wright had a point: Why crowd into downtowns when we could all drive anywhere we wanted?

The car on the expressway enabled large numbers of people to travel long distances on a day-to-day basis. Instead of small railroad suburbs, where housing was restricted to a short radius around stations, drivers spread out across suburbs could now commute 20 miles in 30 minutes. If the streetcar city covered 200 square miles, the 40-mile-diameter expressway city could cover over 5,000 square miles.

Even with growing population, the supply of cheap farmland available for housing development appeared endless, and the cost of a detached house collapsed to be within the reach of the working class. In 1946, a house in Levittown, New York, the prototypical postwar automobile suburb, cost $78,469 in today’s dollars, with little or no money down required. The age of urban sprawl began.

A colorful plan of Frank Lloyd Wright’s Broadacre City. (Courtesy the Frank Lloyd Wright Foundation Archives)

Many older, denser cities began to lose population as residents chased the bonanza of cheap land. The great housing crisis of the 1970s was not a shortage—it was a surplus. When Jimmy Carter visited Charlotte Street in the Bronx in 1977, he saw a whole street of apartment houses lying almost completely vacant. And African Americans—kept out of the suburbs for decades by legal and extra-legal measures—were abandoned within declining central cities.

The problem with dispersion is that people can’t simply live next to where they work, especially in dual-income families. Good luck finding a home next to both a bank headquarters and a steel mill. And, of course, many industries like finance and media thrive on concentration. In the U.S., dispersed cities like Los Angeles and Atlanta ended up having even worse traffic than the relatively concentrated ones like New York City, as hordes of far-flung commuters pressing in daily to get to their jobs.  

Today, like its predecessors, the expressway has struck a technological threshold. Its downfall is its limited capacity. Even the biggest highway can move at most a couple hundred thousand cars per day—sufficient for small cities and for long-distance trips, but inadequate in a city of millions. And while people were once content—or at least powerless to resist—the demolition of thousands of homes and entire neighborhoods for new urban highways, those days are also over.

The city of the future

The constant in transportation technology from the mid-19th to the mid-20th century was change. New modes repeatedly extended the boundaries of cities and changed the way we lived. But that was an aberration over the course of human history. Since then? Not too much has changed. A person can navigate New York City almost perfectly with a fifty-year-old map.

This has had real consequences. In spread-out metros that are growing in population, highways quickly become overcrowded; expanding them is costly and ultimately ineffective. Commute speeds are slowing inexorably as congestion increases. In North America, at least, rail transit is too expensive to build in meaningful amounts and it faces formidable ideological opposition. And the vaunted self-driving car, as imminent and yet illusory as nuclear fusion, will not transform the basic geometry of road capacity. Could they squeeze out a few percent more from the legacy of the 1950s and 60s? Maybe. But that will buy us at most a few years.

The greatest promise for matching technology to the modern worker has always been the idea of divorcing work from transportation entirely: telecommuting. The tools that would enable white-collar workers to clock in remotely have been available for decades and have improved dramatically in the digital era. That could theoretically finally enable Wright’s vision of the complete dispersal of population. But would it? Despite evidence to the contrary, employers remain skeptical of the productivity of remote workers. And any number of human drives keep people stubbornly collocating to be closer to family, friends, and cultural amenities as well as their workplaces. These drives are unlikely to change with technology—and thus, our transportation dilemma is likely to endure.

The best option is to densify our cities. This is hard, too: Adding housing in established neighborhoods will always be more complex and expensive than building on empty farmland. Real estate also remains comparatively cheap in declining or decentralized cities. When many people don’t really care how close they are to the historic urban center, like in Atlanta or Houston, cities can sprawl basically ad infinitum. But the environmental cost is huge, and it’s simply not an option in parts of the country where cities have already grown into each other, like the Northeast Corridor and Southern California.

For a century, we lived off the legacy of rapid innovation. It allowed our cities to grow exponentially and, therefore, the cost of our housing to decrease dramatically. But we’ve now pretty much burned through the benefits of these gains and there aren’t obvious technological saviors on the horizon. We must make do mostly with building up and densifying the urban areas we already have. As transportation goes, so go our cities.

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47 days ago
I wonder how things like 3d printing might affect this.
Olympia, WA

CityLab University: Zoning Codes

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It’s time again for CityLab University, a resource for understanding some of the most important concepts related to cities and urban policy. If you have constructive feedback or would like to see a similar explainer on other topics, drop us a line at editors@citylab.com.

Although invisible on land and inscrutable on paper, municipal zoning codes have a tremendous impact on the form of cities—and by extension, on the way people live in them.

Today, these arcane regulations are seeing unprecedented levels of public scrutiny. After decades of embracing strict zoning rules, several cities and states want to relax them to make it easier to build housing and create more environmentally friendly communities.

This edition of CityLab University offers an overview of zoning and defines the key terms related to it in America, so you can better understand the rules that are shaping your city and neighborhood.


  • Although there were earlier versions of municipal zoning codes, the first comprehensive one was adopted by New York City in 1916.
  • The U.S. Supreme Court decision in Euclid v. Ambler (1926) established the constitutionality of local zoning ordinances and helped set the pattern for what is known as “Euclidean” zoning.
  • Critics of zoning see it as a key driver of sprawl and racial and economic segregation.
  • Beset by a housing affordability crisis, U.S. cities and states are increasingly looking to undo regulations such as R1 zones, parking minimums, and red tape around accessory dwelling units in order to increase the supply of housing.


Municipal zoning in America evolved from a complex set of processes in the first half of the 20th century. In that era, increasingly tall, bulky buildings and industrial expansion were raising environmental concerns for urban dwellers, and a growing suburban homeowner class was flexing its political muscle. Meanwhile, private car ownership offered a new mobility option, and demographic changes led to efforts to maintain racial and economic exclusion.

Embryonic zoning codes existed in America as early as the 19th century, but these tended to govern specific issues like fire safety or apply only to a discrete area. During this period, some developers also attached their own restrictions to lots and homes as a means of ensuring an air of exclusivity and high property values. In Kansas City’s Country Club District in the first decade of the 20th century, for example, developer J.C. Nicholas stipulated the orientation of houses to the street and a minimum construction cost, and he prohibited home sales to blacks. Multiple cities passed race-based zoning ordinances in the 1910s; the U.S. Supreme Court struck down Louisville’s, but cities’ attempts at enforcing residential segregation continued.

In 1908, Los Angeles adopted the country’s first municipal zoning ordinance, creating residential districts prohibiting “nuisance” uses such as laundries and separate industrial districts. But the first comprehensive zoning code in the United States was New York City’s 1916 Zoning Resolution, which came amid concerns that new skyscrapers like the monolithic, 41-story Equitable Building were blocking light and air from the streets. The 1916 rules required new towers to become narrower as they grew taller, resulting in the “wedding-cake” setbacks seen in iconic skyscrapers like the Empire State and Chrysler buildings.

A decade later came the legal basis for many municipal zoning codes in America—its name derived not from the ancient Greek mathematician Euclid, but rather from the humble Cleveland suburb of the same name.

In 1926, the U.S. Supreme Court heard the case Village of Euclid v. Ambler Realty Co. and decided in favor of Euclid, Ohio’s power to dictate land use. This affirmed that municipalities had the constitutional authority to regulate which uses could go on which parcels and other aspects of buildings on private property.  

Anyone who has played Sim City will intuitively understand Euclidean zoning. Each piece of land has a single, specifically allowed use. (Typical uses include agricultural, residential, commercial, industrial, institutional, and open space.) On a zoning map, different land-use types are indicated by different colors, and the density or intensity of development is shown by darker and lighter shades, as on Euclid’s current zoning map.

Following Euclid v. Ambler, many municipalities across the country adopted Euclidean zoning laws, which ensured that homes (usually those belonging to more affluent white people) would be far from factories and other undesirable land uses. These laws also helped preserve open space and historic neighborhoods and protected home values in new suburbs. African American neighborhoods often got zoned for the uses white Americans didn’t want near them, causing property values in black neighborhoods to erode and further entrenching segregation.

When private cars became the dominant mode of transportation and fewer people walked to work or on errands, areas zoned for a single use got bigger, according to Sonia Hirt in Zoned in the USA. Lower-density zoning and parking minimums have had a huge impact on the look, functioning, and carbon footprint of American cities.

Many scholars view Euclidean zoning as a key factor in America’s urban sprawl and racial and economic segregation. However, Houston—the largest American city without a municipal zoning ordinance—is also sprawling and segregated, making it at least a partial counterpoint to these arguments. (Despite its lack of zoning, Houston does have non-zoning regulations that accomplish some of the same things.)

Separation of uses remains a fundamental principle of most zoning codes, even as form-based and incentive zoning gain in popularity (neither of which is mutually exclusive with Euclidean zoning). The true opposite of Euclidean zoning is mixed-use zoning, which allows for the apartment buildings with ground-floor shops beloved by Jane Jacobs. The movement known as Smart Growth promotes mixed-use, high-density development near mass transit, and has inspired new zoning guidelines in Massachusetts, California, and elsewhere.


The following is a glossary of terms that are key to understanding this wonky-but-important arena of law and policy. (Click a letter below to skip ahead to the relevant entries.)


  • Accessory use/accessory dwelling unit
  • Air rights


  • Classifications (R1, etc.)


  • Euclid v. Ambler
  • Exclusionary zoning


  • Floating zones
  • Floor area ratio
  • Form-based code


  • Incentive zoning
  • Inclusionary zoning


  • Lot coverage


  • Minimum lot size
  • Mixed-use zoning


  • Nonconforming use


  • Overlay zone


  • Parking minimum
  • Performance zoning
  • Planned unit development


  • Setback
  • Spot zoning


  • Upzoning


  • Variance


Accessory use/accessory dwelling unit

(Giordano Poloni)

An accessory use is a structure or improvement that enhances or is required by the primary use of the lot. Accessory uses do not have to follow the same rules as structures permitted under conventional zoning, since they are not the primary purpose of the lot, and are usually much smaller and less noticeable than the main building. Examples of accessory uses include garages and vending machines.  

The most discussed accessory use of late has been accessory dwelling units (ADUs), also known as in-law suites, backyard cottages, or granny flats. Particularly popular following loosened restrictions in housing-starved West Coast cities including Vancouver, Portland, and Los Angeles, ADUs are small housing units built in the garage, attic, basement, or backyard of another building.

ADUs tend to be cheaper to build than a traditional housing unit—one study found that ADUs in the Pacific Northwest cost an average of $156,000 to construct, excluding land costs—and their more modest visual impact makes them an easier sell to change-averse neighbors. Rental income from an ADU can help homeowners afford to remain in increasingly expensive cities, or keep multi-generational families together. Still, ADUs remain bureaucratically difficult to build, if not completely illegal, throughout most of the country.

Air rights (see Floor area ratio)


Classifications (R1, etc.)

Also known as zoning categories or symbols, these letter-number combinations represent the nuts and bolts of what is and isn’t allowed on any given parcel in a city. There is no universal standard for zoning classifications, but many cities indicate the use with a letter or combination of letters (R for residential, C for commercial, and I for industrial, for instance), and the density or intensity of development with a number.

In addition to use and density, zoning categories also serve as shorthand for a number of key design requirements, including height limits, setbacks, and floor-to-area ratio (FAR), as indicated in the table below. Zoning classifications can be incredibly specific: Jacksonville, Florida, for instance, has 11 different categories for low-density residential parcels alone.

Examples of zoning classifications, City of Los Angeles

(Source: Department of City Planning, Generalized Summary of Zoning Regulations)



Min. area per lot

Min. area per unit

Min. lot width

Car parking required


Agriculture: One-Family Dwellings, Parks, Playgrounds, Community Centers, Golf Courses, Agricultural Uses)

5 acres

2.5 acres

300 ft

2 spaces per dwelling unit


One-Family Residential: One-Family Dwellings, Parks, Playgrounds, Community Centers, Truck Gardening, Home Occupations

5,000 sq ft

5,000 sq ft

50 ft

2 covered spaces per dwelling unit


Multiple Dwelling:  Apartment Houses, Churches, Schools, Child Care, Homeless Shelters, Clubs, Lodges, Hospitals, Sanitariums, Hotels

5,000 sq ft

200 sq ft

50 ft

1 space per unit < 3 habitable rooms; 1.5 spaces per unit = 3 habitable rooms; 2 spaces per unit > 3 habitable rooms; uncovered 1 space each guest room (first 30)


Euclid v. Ambler

The facts of the case: Ambler Realty owned 68 acres of land in Euclid, a Cleveland suburb. Euclid adopted a zoning code in 1922 that split the land into separate districts and prevented Ambler from developing some of it for industrial purposes. So the company sued, arguing that the zoning had significantly reduced the value of the land, and violated the Fourteenth Amendment’s protections of liberty and property.

In a 6-3 ruling, the court decided against Ambler, finding that the zoning ordinance did not exceed the local government’s power. While Ambler had hoped to develop industrial uses on its land, the decision was partly a referendum on the social value of apartments. “[V]ery often the apartment house is a mere parasite,” Justice George Sutherland wrote in his opinion, bringing “disturbing noises incident to increased traffic and business” and “depriving children of the privilege of quiet and open spaces for play.”   

Exclusionary zoning

Even after the passage of the Fair Housing Act in 1968, zoning continues to be used to maintain racial and economic segregation by preventing less expensive types of housing, often in desirable neighborhoods. Requirements such as large lot sizes and parking minimums make it hard or impossible to build smaller, less expensive housing that middle- and lower-income residents would be able to afford. This often translates to a neighborhood’s high-quality public schools and proximity to jobs being “off limits” for people without the means to buy in. So exclusionary zoning works to concentrate poverty in areas that lack such strict rules.


Floating zones

Floating zones are a type of spot zoning that change the zoning laws for a particular area with conditions that “float” until a developer proposes a plan that can meet those conditions. Floating zones can be used to encourage specific types of land uses in a particular area, including affordable housing, commercial districts, or environmentally friendly developments.

Floor area ratio (FAR)

(Giordano Poloni)

Floor area ratio (FAR), or the ratio of floor area to lot area, is a metric for regulating the number of square feet that can be developed on a parcel without specifying the exact shape and size of the structure. For example, a FAR of 5.0 means that a builder can develop five times as much square footage as exists on the lot. FAR is a metric within a rubric known as performance zoning, which includes other dimensional ratios to preserve open space, light, and air.

FAR requirements do not by themselves prescribe a particular building shape. A parcel with a FAR of 2.0 could include a four-story building covering 50 percent of the lot area, or two two-story buildings each covering one-quarter of the lot. These requirements often exclude basements, attics, and parking garages, and are usually coupled with more specific regulations pertaining to setbacks and height.

FAR is particularly relevant in New York City, where it is part of the formula for determining the transferable development rights, commonly known as “air rights,” for new towers. If a lot is currently improved with a building smaller than the allotted FAR, the owner of that building can sell those air rights—or excess FAR—to the developer of an adjacent property. By cobbling together air rights from other properties, a developer can build much higher than the allotted FAR on their lot.

This “cap-and-trade” system has been a driving force in the development of supertall towers in Manhattan. Critics of these policies have released a series of reports called “Accidental Skyline,” which criticize the city’s policies around air right transfers and other enabling policies for supertall towers, like by-right approvals and the mechanical voids loophole, which the city recently reformed.

Form-based code

Rather than focusing on land use, form-based zoning codes regulate design elements, including the size, style, and placement of buildings. Form-based codes tend to promote walkability and more compact development patterns, since they allow different land uses to be closely intermingled.

Whereas Euclidean zoning often deals in minimums or maximums—like maximum height limits or minimum setbacks or parking requirements—form-based zoning is more prescriptive, requiring specific ranges for height, bulk, setbacks, and even more minute design details like signage, landscaping, and architectural ornamentation. Form-based zoning has been championed by New Urbanist architects and planners, who are interested in creating denser pedestrian neighborhoods, often with a traditional architectural vernacular.

Denver’s zoning code includes several “neighborhood contexts,” including suburban, urban edge, urban, general urban, and urban center. They are distinguished by building placement and height; “street, alley, and block patterns;” and “diversity of mobility options.” The adoption of these form-based codes in 2010 did not eliminate Euclidean codes: Of the city’s 25 neighborhood-context districts, 12 are exclusively residential, according to Sonia Hirt.


Incentive zoning

This permits greater density, fewer parking spaces, and other developer perks in exchange for contributions to the public good, like parks, transportation infrastructure, or affordable housing, as in inclusionary zoning policies. Incentive zoning can be used to guide developers to certain outcomes without making them legally mandatory. Successful incentive zoning usually requires land values to be sufficiently high for developers to be willing to incur additional costs.

Inclusionary zoning (see Incentive zoning)


Lot coverage

Lot coverage is the bird’s-eye-view footprint of a structure—in other words, the proportion of its lot that it covers up. Unlike FAR regulations, lot-coverage rules do not regulate the livable square footage of a building, but rather how much space it takes up at ground level.

Lot-coverage maximums mandate that a development’s footprint cannot exceed a certain percentage of the lot. In the affluent Bay Area suburb of Tiburon, for example, houses in R1 zones can only cover 30 percent of the lot. These restrictions maintain a semi-rural character in many suburban neighborhoods, and can also provide environmental benefits related to fire protection and water drainage.

Similar to lot-coverage maximums, minimum lot sizes are in force in many suburban neighborhoods and towns wishing to preserve a natural feel. Parts of Greenwich and Stamford, Connecticut, have minimum lot sizes of three acres or more. Despite providing some environmental benefits, these kinds of restrictions have the effect of increasing car dependence by ensuring buildings are far apart from one another; they have also been criticized for being a tool of segregation, wherein all potential residents must be able to afford a massive lot.


Minimum lot size (see Lot coverage)

Mixed-use zoning (see History)


Nonconforming use

A nonconforming use is a structure or design element that is not legal under current zoning. Many nonconforming uses—like an apartment building in a neighborhood that was zoned for lower density, or a store in an exclusively residential zone—are grandfathered in. But if a building is destroyed, whether by demolition or disaster, it can’t always be rebuilt to the same density or for the same use.

ADUs are a common nonconforming use that is increasingly being legalized. In some cities and states that have relaxed ADU rules, property owners with previously nonconforming ADUs can pay a fee, get their property inspected, and get it legalized.


Overlay zone

An overlay zone or district enacts special zoning rules in a designated area that supersede or alter the existing zoning. Usually, overlay zones are more strict than the existing zoning and are intended to protect sensitive local environmental or design features. For example, overlay zones can be implemented in flood-prone areas, adding special vegetation requirements or impervious surface maximums.


Parking minimums

Parking minimums are the number of off-street parking spaces required for a new development. Different uses trigger different parking requirements: In Los Angeles, the first city in the nation to adopt parking minimums, gyms, restaurants, nightclubs, and coffee shops must provide one off-street parking spot per 100 square feet. Single-family homes require two off-street spots, and apartment buildings with more than three units must include one parking spot per unit. However, various incentive-zoning policies and special zoning districts make these requirements fungible in many circumstances.

Parking minimums began popping up in the 1920s and ‘30s when the availability of parking started to become a major issue in cities. These laws, which exist in virtually every city with a zoning code, have remained largely unchanged until recently, when a convergence of trends has caused cities to rethink their efficacy.

In expensive cities, the $25,000 to $50,000 for each off-street parking spot only serves to make housing more expensive while limiting the amount of space that can be devoted to housing. And in dense urban areas, the rise of ride-hail apps, car-share, and bikeshare, combined with good old-fashioned walking and transit, have made personal car storage a less urgent issue.

As “a fertility drug for cars,” in the words of UCLA professor and parking guru Donald Shoup, parking minimums induce demand for driving, amplifying all of the other challenges associated with cars, including traffic, safety, and greenhouse gas emissions.

San Francisco made national news last year when it eliminated parking minimums, but Hartford and Buffalo had quietly done so the year before. (Many cities have eliminated parking minimums in downtown neighborhoods and other special districts, but not throughout the entire city.)

In Sandpoint, Idaho, the developer of a three-story office building realized it would be more cost effective to buy and demolish neighboring historic commercial buildings to accommodate the project’s required 218 off-street parking spaces than to include them in the new building, according to the organization Strong Towns. The events in Sandpoint caused the city to revise its parking minimums, enabling at least four new developments that would not have been allowed under the previous rules.

Performance zoning (see Floor area ratio)

Planned unit development (PUD)

Planned unit developments are developments that are not subject to standard “by right” zoning, but are allowed greater flexibility by the local government. Developers may submit a project as a PUD to be able to build more densely or on a challenging parcel of land, in exchange for providing community benefits such as affordable-housing units or a park. In Washington, D.C., PUDs have taken off in recent years, and so have lawsuits aiming to block them.



Setbacks are the minimum distance a structure must be from the edges of the property line. Not to be confused with setbacks as an architectural element (like those that became popular in New York City following its 1916 zoning ordinance), setbacks in zoning parlance are a key part of the ground-level experience of the city. Setbacks provide a sense of uniformity to a city block, and ensure that windows receive adequate light and air.

As is the case in many jurisdictions, Santa Clara County, California’s setback requirements include exceptions for elements like awnings, bay windows, decks, basement light wells, and ADA-accessible infrastructure. R1 single-family home zones with 5,000-square-foot lots in unincorporated Santa Clara County or in cities without their own zoning ordinance have front and rear setbacks of 25 feet apiece, and side setbacks of five feet.

Spot zoning

Spot zoning is a negatively charged phrase that refers to a rezoning for a particular parcel or project that does not conform to a city’s zoning code. It gives developers a way around the long and arduous process of changing the zoning ordinance. Critics see spot zoning as a corrupt strategy to bypass traditional planning processes and provide special advantages to favored developers. Instances of spot zoning have often been successfully challenged in court, according to Hirt: Legislators have to prove that such zoning changes are in the public interest, and must be compatible with the existing zoning code in its impact on the community, if not according to its design specs.



Upzoning is the rezoning of land to allow for more intense use (e.g., a higher FAR) or a change in use (e.g., from residential to mixed residential/commercial). It is often framed as a strategy to combat exclusionary zoning. Minneapolis eliminated R1 zoning in its 2040 plan, allowing residential buildings of up to three units in all residential areas, and Oregon just passed a similar statewide law. California’s SB50, an upzoning bill that prioritized transit and employment hubs for more density, stalled out in the state legislature this May. (Want less density? That’s downzoning.)



A variance is a zoning change that is granted to a developer by a government body on a discretionary basis, often following public hearings. Developers might ask for relief from certain requirements, citing project-specific financial or practical difficulties. Variances are often related to architectural details. One Chicago apartment developer recently requested a variance to exceed the parcel’s height limit by 6 feet to include higher ceilings in the five floors of apartments below.

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Expiration Date High Score

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"Wait, we've MOVED since 2010. How on Earth did--" "Look, some of us were just born to be champions."
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The Three Cards That Should Be Banned in Modern

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Brian DeMars Modern is in need of a shakeup, and Brian is prepared to go further than just Hogaak. What else does he think should get the banhammer?5 Jul, 19Brian DeMars
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What does a medical exemption from vaccination mean in the Olympia School District?

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Measles can be prevented.

Medical exemptions for vaccinations in the Olympia School District and Washington State might not be what they appear to be.

On their face, these exemptions allow children who cannot be vaccinated (because of weakened immune systems, for example) to waive vaccination requirements and attend school. But, from what I've been able to gather from a public document request from the Olympia School District, the differences between personal-belief and medical exemptions is murky.

So murky that (please read to the bottom), I wonder if doctors or any medical professionals are necessary for the medical exemption process.

Let's work backward first to see how I got here:

About a month ago, while the measles outbreak in Clark County was still new news, I updated what the vaccination rate for schools in Olympia was like. This was similar to other times I'd done this update, there are some scary high exemption rates in Olympia schools. But this time I noticed a new wrinkle: the top schools for personal-belief vaccine exemptions were also the top schools for medical exemptions.

Top Medical (bold if on both):

1. Olympia Community School (12.9 percent)
2. ORLA Montessori (8.5 percent)
3. Olympia Regional Learning Academy (6.3 percent)
4. Lincoln Elementary (4.6 percent)
5. Pioneer Elementary (2.7 percent)

Top Personal (bold if on both):

1. Lincoln Elementary (19.4 percent)
2. Avanti High School (17.6 percent)
3. Olympia Community School (16.1 percent)
4. Olympia Regional Learning Academy  (15.8 percent)
5. ORLA Montessori  (15 percent)

To me, this made little sense. If you were a parent of a child who had a medical reason to avoid immunizations, then I think you'd want to then use the herd immunity at your child's school to help prevent infections. What I could see was that there was a correlation between parents who would seek a personal exemption from vaccines, ones that would seek a medical one, and the school they chose.

That made me assume that parents who are seeking medical exemptions are also not necessarily afraid to send their children into environments where a scarily low percentage of the children are vaccinated. This got me curious about the nature of medical exemptions in the Olympia School district overall.

So, I made a public records request for all medical exemption forms that represent active students in the Olympia School District. These are the documents I received and this is the spreadsheet I put together summarizing what I found (folder with both files here). The district blacked out student names and addresses before they gave me the documents, but they didn't black out the names of doctors that signed medical exemptions.

Here is what I sussed out:

1. Naturopaths are slightly more likely to sign medical exemptions. While 25 percent of the medical exemptions I received from the school district, naturopaths only make up 20 percent of the provider types (family, pediatric and naturopath) that I assume would likely be presented with the form. Some forms were also signed by physician assistants and nurse practitioners.

2. Some doctors sign more than others. Like schools that seem to collect medical exemptions, some doctors seem to sign more than their share. This may be a consequence of who they see (people that are more willing to ask for a medical exemption), but I will probably never find that out. While a vast majority of the doctors who signed the forms only signed one, there were a few that signed several:

Jennifer Ash ND, 7
Lisa Barer MD, 6 
Amy Belko MD, 4
Bridget Sipher MD, 4
Kevy Wijaya MD, 4
Richard Faiola NP, 4

3. What does a medical exemption even mean? Over 75 percent of the forms had both the "medical" box and "personal" exemption marked on the form. This seems to undercut the meaning of the medical exemption form altogether. What may seem like an inexplicable bunching of both medical and personal belief exemptions (why would an immune deficient child attend a school full of unnecessarily unvaccinated children?) isn't. What it really could be is just a larger group of children whose parents declined vaccination for personal beliefs but got their doctor to sign a medical waiver.

Then there was this:

You might have already perused the documents the school district gave me, but if you haven't, this is (as far as I can tell) a full-on medical exemption form with no details, exempt the student's name and a parent's signature. No medical professional's name, no medical professional's signature. This isn't even a double-marked personal/medical exemption. This is a pure medical exemption that is on file at the Olympia School District, that purported to clear a student to have not been vaccinated for medical reasons, with no medical professional's name on it. 

If a parent can sign a medical exemption form and it be accepted by the school district, what is the point of even requiring them at all?
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