Single Family Zoning: It's All About the Lot Sizes

Contemporary critiques of zoning take several forms.  First, and probably most common, is the critique of strict use segregation in the Euclidean manner, with commercial and residential areas segregated to greater or lesser degrees.  An increasing focus has lately been placed on the relative preponderance of single-family detached residential zoning within urbanized areas.  A third line of critique, which has received somewhat less attention although it has been the subject of numerous academic studies over the years, looks at minimum lot size requirements within both single-family and multifamily zones.

Although it may seem like a minor subject next to the first two critiques mentioned, the second critique is incomplete without examining permitted lot sizes.  For instance, even though a city may have substantial areas set aside for multifamily housing, if the minimum lot size per apartment unit (or floor area ratio equivalent) is approximately equivalent to single-family zones, the density and/or affordability difference may be minimal.  Alternatively, the single-family detached ("SFD") zoning designation, by itself, tells us little about the density of the area.  Depending on the lot area required and right-of-way widths, SFD densities for a given household size can range from 300/square mile to as much as 25,000/square mile or more, all without the need for any party walls.  

A few concrete examples can help illustrate the point.  In the American context, despite the presumed consumer preference for SFD homes, neighborhoods of homes on very small lots and using narrow rights-of-way, such as are abundant in many other countries, are quite rare.  In the entire New York metropolitan area, for instance, there are only a handful of such neighborhoods, mostly those intended as beachside retreats along the southern shore of Brooklyn and on the Rockaway Peninsula.  One such neighborhood is shown here:

This is Gerritsen Beach, in Brooklyn, showing parcels of 1,800 square feet on a right-of-way (property line to property line) of 28'.  The 2010 Census gives a population density of over 17,000/square mile, about half of the average for Brooklyn, although this may be affected by the presence of second homes.  As Nathan Lewis has shown, similarly scaled neighborhoods in Tokyo attain densities exceeding 30,000/square mile.  Even so, it is about 80% denser than the densest SFD suburbs built in Nassau County during the 1940s-1970s.  It is more than twice as dense as Levittown itself, and denser even than the three-decker neighborhoods of cities like Worcester, MA or New Haven, CT.  The New York metro area has a conspicuous absence of neighborhoods of this density and type, with Census tracts swiftly falling off from around 25,000/square mile to 10,000/square mile.

Beach neighborhoods seem to be popular settings for this type of design, as a similar (but slightly lower) density is present in Long Beach, California, shown below.  Lots are around 2,400 square feet with a 40' right of way and alleys of 13' (comparable density appears to be achieved through presence of small apartment buildings):  

And here is Levittown itself, with lot sizes of around 6,000 square feet and right-of-way (between outer sidewalk edges) of 50'.  Population density is approximately 7,500/sq. mi.:  

The Levittown homes in their initial form, intended for the large families of the Baby Boom era, were actually somewhat smaller (800 sq. ft.) than the 1920s vacation cottages of Gerritsen Beach (1,000 sq. ft.).  The contrast of very small houses with lots the same size or larger larger than those typical of the pre-1940 period seems to have been characteristic of the time period, perhaps related to the increased cost of labor following the Great Depression combined with stable land values.  The more spacious lots may have offered some compensation for the modest interiors.

At the extreme is the ultra-low density of interior but non-rural New England, showing 2- and 3-acre lot zoning (here, in Easton, Connecticut), accompanied by wetlands regulations, with population density of around 260/square mile:

Now, if a rapidly urbanizing country wished to offer the possibility of ownership of a SFD home to the greatest possible portion of its population, the obvious policy goal would be to allow construction of a SFD home on any size lot desired, and on streets as narrow as possible so as to minimize economic waste.  The result is very much what we see in most of the wards of Tokyo as well as in Gerritsen Beach: very small lots but with practical (square-shaped) dimensions along narrow streets and no alleys.  Where multifamily buildings are not prohibited, these will be interspersed here and there, sometimes occupying two or three lots.

In practice, however, American zoning does not take this approach, with the sole exception of mobile home parks (which I've discussed here).  Not only are lot sizes strictly regulated for SFD zones, generally to standards far in excess of what is needed for a comfortably-sized home, other policy measures are in place that make small lots difficult to build as a matter of economics, such as:

• Apparent aesthetic preference for large, widely space multifamily over densely packed single-family in multifamily zones.  Although small multifamily buildings have fallen out of zoning fashion, if they were ever popular, those zones that survive have some curious features.  For instance, one Connecticut town's code, typical of the type, effectively grants density bonuses for building duplexes and triplexes over building two or three standalone houses on the same lot.  In the densest zone it is possible to build a single-family home on 5,000 sq. ft. -- the smallest SFD lot permitted in any zone -- but a duplex requires only 7,500 sq. ft. and a triplex only 9,000.  The policy intent here is not obvious, but implies aesthetic favoritism for retaining large dwellings with generous spacing even at the expense of the single-family ideal.  
• Minimum street widths.  Although these do not affect the lot size directly, mandated wide streets make small lots for SFD a less economical proposition.  For instance, were the Gerritsen Beach lots placed along the Levittown right-of-way, each 1800 sq. ft. lot would look out onto 3,000 sq. ft. of sidewalk and roadway!  The neighborhood, overall, would have a ratio of 1.2:1 of private land to right-of-way, or, in other words, only 55% of the land would be in private lots for sale.  Levittown's ratio is a far better 3:1.  With a 28' right-of-way, Gerritsen Beach's streets are already about as wide as economically possible in light of high land values, and streets of Japanese dimensions would yield a far better ratio.

The design differences produce some noticeable differences even at the very large scale.  The prefecture of Tokyo, with population 13.2 million, has a homeownership rate of 45%.  The city of New York, with population 8.4 million, has homeownership of 32%.  Although the prefecture's density is lower than New York's (16,000 vs. 28,000/sq. mi.), Tokyo's outer suburban areas are so much denser than New York's that its metropolitan area density is higher.  For the entire metro area, Tokyo maintains a 56% homeownership rate with 47% share of detached houses, as compared to New York with 52% homeownership and 36% SFD share.  Los Angeles, to pick another example, has 49% homeownership with 50% SFD stock.

A metro area of more comparable size to New York's, such as Kyoto-Osaka-Kobe, has a homeownership rate of 58%, higher than the entire state of New York, and not much lower than far smaller American cities commonly associated with low-density SFD housing such as the Houston MSA (60%), Dallas (61%), Atlanta (63%) and Phoenix (63%).

Interestingly, the issue of minimum lot sizes appears to be one on which there is general agreement between the Smart Growth faction and the defenders of suburbia, as Wendell Cox wrote some years ago in response to critique from the Brookings Institute:

"I was even more surprised at the claim that I defend 'anti-density zoning and other forms of large lot protectionism.' Not so. 

Indeed, I agree with [Jonathan] Rothwell on the problems with large lot zoning. However, it is a stretch to suggest, as he does, that the prevalence of detached housing results from large lot zoning. This is particularly true in places like Southern California where lots have historically been small and whose overall density is far higher than that of greater New York, Boston, Seattle and double that of the planning mecca of Portland."

I think that Cox is correct here, but not even as correct as he could be.  Large-lot zoning not only does not cause a prevalence of SFD housing, it limits it, as shown in the New York metro area.  Los Angeles' metropolitan density is substantially higher than New York's (a point often raised to incredulous reaction), but its share of SFD stock is much higher.  To point out in response to an allegation that a city is heavily zoned for SFD that a majority of its housing units are in multifamily structures (in the case of Seattle, at the link) only underscores the point.

Although most studies have found that minimum lot sizes do affect overall development density (that is, developers appear to build at or near the minimum lot size allowed), one study of Maryland suburbs of Washington, D.C. found that, except in the case of areas with very large minimum lots sizes, developers were subdividing into lots larger than the mandated minimum, including in cases where planned unit development options left them with a free hand to build denser than the zoning code superficially allowed:

"We then examine the extent to which lot size is being constrained by regulation by comparing actual subdivision density to the allowable density under zoning rules. This analysis is done for three counties with different degrees of suburbanization. We find that only in the areas with the very large lot zoning does zoning seem to be constraining actual lot[] size. There is a good deal of excess capacity in the density that could be built, especially in the more densely zoned areas." Lot Size, Zoning, and Household Preferences:Impediments to Smart Growth?

There might be no concern with low-density development at the fringes of metro areas except that such areas, once built up, are politically almost impervious to change.  Some cities have implemented maximum lot sizes, but these are generally very generous and only apply in certain areas.  The misunderstood achievement of the New Urbanism, and the Maryland suburb of Kentlands in particular -- whatever its faults in design detail -- was that small lot single-family housing developments not only need not be qualitatively inferior to the 6,000+ sq. ft. tracts that characterized the post-1940 suburban era, and that they could even offer amenities that made them superior residential environments.  Where regulatory mandates fail, leading by example can succeed.

Kentlands, with SFD lots from 5,600 to 2,600 sq. ft, and with ROWs ranging
from 45 ft. to 12 ft. on alleys.

Related posts: None of mine, but Nathan has written several great pieces on the topic which you can find at his website.

Housing Dreams, American and Mexican

In the previous post, I observed how newly-built single-family housing in the Mexican border city of Matamoros (and in fact in most Mexican cities) is both much smaller in size and far cheaper, even adjusting for lower incomes, than almost any housing in the United States outside of Detroit.

New Matamoros rowhouses. (Google Maps).

This is partially due to the underdevelopment of the mortgage banking industry in Mexico, with the result that six percent of all homes in the country are financed with mortgages. The vast majority of homes are either inherited, bought with cash, or else are self-built on cheap vacant land, although informal lending systems among friends and family members no doubt lie behind many of these cash purchases. In the absence of debt-financed home consumption, most new homes must be very modest to match the limited purchasing power of potential buyers. 

Although one might expect this lack of financing to impair individual property ownership, a surprising 80 percent of Mexicans own their own homes. This compares to a rate of only 65 percent in the United States, where 70 percent of homes are encumbered with mortgages and only 1 in 10 buyers pays in cash (at least, until the recent surge in buying by institutional investors). As I pointed out in a previous post, the homeownership rate in the US has actually been more or less stagnant since the mid-1960s in spite of extraordinary efforts to expand the availability of credit.

I think there is something else at work here, though, beyond the influence of two very different lending environments, and it relates back to the modest size of houses observed in Mexican cities. It's been a point often noted that the average size of new American homes has been steadily increasing since 1950 even as household sizes have fallen. Home sizes and household sizes have diverged so sharply, in fact, that a major structural mismatch has emerged throughout the US housing market, as shown below (charting percentages of all US housing units and all US households):

Data from 2012 ACS three-year estimates.

Although over 60% of US households consist of just one or two people, only 13% of housing units are studios or have one bedroom. Moreover, we know that very few single-family homes of the type produced over the past few decades years have been studios or one bedrooms (or even two bedrooms), making it likely that most of these units are apartment rentals. This can be confirmed through housing data on tenure status, which show that studio and one bedroom units are overwhelmingly renter-occupied:

Data from 2012 ACS five-year estimates.

Homeownership in the United States, evidently, is very much a large or larger-home phenomenon (assuming that number of bedrooms is a reasonable proxy for housing unit size). When owned units are looked at in isolation, this fact becomes even more startling:

Data from 2012 ACS five-year estimates.

In essence, new single-family detached or attached homes intended for just one or two people, of the size built in mass quantities in Mexico, virtually do not exist in the United States. A Zillow or Trulia search in most any major American city will quickly show that this type of home largely ceased being built after the late 1950s, which, perhaps not entirely coincidentally, is about the same time that the homeownership rate began to level off. Today, only about one in ten new single-family homes have two or less bedrooms. Although this might be understandable if the decline had been offset by significant increases in the proportion of small units in multifamily buildings, it turns out that this has not been the case.

To what extent these patterns are an expression of consumer preferences, market forces, financial and tax incentives and/or land use restrictions (such as minimum lot or square footage restrictions) is unclear, although there is evidence that square footage restrictions generally seem to have appeared at around the same time as smaller homes ceased being built in large numbers and to have increased in restrictiveness thereafter.* Very small houses, and very small lots, have in typical American zoning fashion been segregated and stigmatized in so-called trailer parks (note that Matamoros, despite being poorer than any American city, apparently has no trailer parks).

Tiny House movement circa 1921:
"Just the thing for two people!"

Whatever the explanation, the effect must be to impede further increases in homeownership. As the country has undergone a long-term reduction in household size, the market has produced fewer and fewer for-sale options sized for small households. The options that remain are not ideal. One can either buy a home that is far larger and more expensive than one needs or enter a competitive rental market for legally restricted multifamily supply (large swaths of American cities, due to restrictive zoning, have few or no apartments for sale at all). An additional option — subverting late 20th century cultural norms* by renting out rooms within a single-family dwelling larger than needed for just one or two occupants — invariably raises the hackles of incumbent homeowners (as seen in the occupancy limit controversy in Austin and many other cities).

These trends have been noted countless times before, in particular by Christopher Leinberger, while Nathan Lewis has been adamant about the need for an increase in production of much smaller homes (including multifamily construction) and, just as importantly, the availability of much smaller building lots. Americans seem to have some difficulty conceptualizing separately-owned very small homes on small lots, though, and even when structures of this size are recognized as meeting an important market need, they are typically imagined as mere accessories to "proper" single family homes, not least by the New Urbanists themselves. Still, that is an approach that tries make something better out of the traditional American pattern of building a series of small houses (on their own separate street network!) just for cars to live in:

Indianapolis residential alley with garages, origin ca. 1920s. (Google Maps).

The Tiny House movement, which partly emerged in reaction to the financial burden imposed by large homes, has no such hang-ups, though the emphasis seems to be almost exclusively on shrinking the size of the home, rather than the size of the lot, and is often associated with rural environments (though certainly not always, and also see here). But large houses seem to be a natural fit for oversized lots and overbuilt infrastructure, as Nathan Lewis has noted.

What would be a reasonable price goal, within the context of the dominant single-family detached form, for housing cost using both small homes and small lots? Nathan, in his writings on this subject, aims for $50,000, which, when adjusted for higher American incomes, would be roughly comparable to the greenfield homes of Matamoros. Nick Derome estimated $170,000 for very small-lot homes in surburban Toronto in comments on the previous post. For even the highest cost towns in Fairfield County, Connecticut, based on land prices, 1,000 sq. ft. homes of less than $200,000 appear financially (if not politically) feasible. Going almost anywhere else from such a high cost location, prices should drop significantly.

Even within certain parts of ultra-expensive Fairfield County itself, the few manufactured and/or mobile homes available for sale (the only type of contemporary single-family detached housing that, with its special zoning designation, has anywhere close to the lot sizes found in Matamoros) tend to run around $60,000 for a 1,000 sq. ft., two-bedroom home. Higher quality architecture and construction — such as that found on the Katrina cottages or better — could surely be provided at only somewhat greater expense. A major challenge, it would seem, is not simply surmounting legal barriers, but reaching an understanding that small homes are not just for poor families, but for small families and others too.

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Related posts: It turns out I'm not the first to connect Tiny Houses and Mexican urbanism -- an American homebuyer in the Mexican city of Merida linked the two on his blog here. Also, Life Edited opines on Why Household Size Matter and Why Are American Homes So Big?

*In striking down a Connecticut town's law fixing the minimum home size at 1,300 square feet (under challenge by a builder attempting to construct a 1,000 sq. ft. modular home), the Connecticut Supreme Court noted "the significant increase of the minimum floor area requirements over the years since 1955 when [the town] had its first regulation controlling minimum floor area requirements. At that time, the minimum floor area requirements were only 750 square feet for a one-story house... ." Builders Service Corporation v. Planning & Zoning Commission (1988). Similar New Jersey ordinances dated as early as 1949.

*Consider the connotations of the very term "single-family dwelling" and what it implies about the identity of the inhabitants of such a dwelling. However, such creative use of single-family dwellings used to be very common, legal and accepted as more or less ordinary (for an example, browse the appendix of the 1950 Housing Census, which describes a bewildering array of housing arrangements within a single home that enumerators might encounter).

Nathan Lewis on "Stuff that Works," and New Narrow Streets Advocates

Nathan's latest, Let's Take a Traditional City Break 5: Stuff that Works, is now available on his site; In it he features a new development in Burlington, Ontario, mentioned here by commenter Nicolas, which has adopted a genuinely traditionalist design format. Nathan also mentions a promising new site, SmallStreets.org, which as far as I know is the only narrow streets advocacy organization out there. Is the movement gaining steam? Nathan's writings are cited as an inspiration for its creators, but they've very kindly linked to this blog as well. Check them out – there's a lot of great material on there so far, and I'm sure more will continue to be added.

Umbrian street at right.

New World Economics on the New New Suburbanism

Note: I'll be reposting Nathan Lewis' urbanism-related content as it becomes available.  Feel free to comment on his articles here.

In his latest post, Nathan Lewis wants to tell you how to make a pile of dough with the traditional city, and has provided illustrative drawings and calculations to show exactly what he has in mind, among many other observations on the New Urbanism, the history of American home sizes, and the issue of affordable housing:

"City governments everywhere wonder how to create "affordable" housing, but how is that possible when everyone has to buy way too much land, and build a house that is way too big, and also indirectly support an incredibly excessive roadway system, and a system of school buses for the public school, and also a second or third car to get around this ridiculous landscape? The larger houses themselves have a certain logic: once you have the way-too-big land plot, the second and third car, and the vastly excessive roadway system, you might as well go whole hog and get the big house too. You're already 80% committed."

 It's an in-depth piece, but I strongly recommend reading through the whole thing.

New World Economics on Single-Family Solutions

Nathan Lewis' latest is now available: How to Make a Pile of Dough with the Traditional City 4: More SFDR/SFAR Solutions.  Nathan addresses the very basics of urban form: the relationship of block depth to street width, lot dimensions, and accommodating cars into a dense urban fabric.  Feel free to leave comments about it here.

One underlying point is similar to the one I made in last week's A Tale of Two Densities: to create a neighborhood that is both 1) mainly single-family, attached or detached, and 2) is dense enough for walkability, blocks must be shallow, and if blocks are shallow, streets must also be narrow, or else the ratio of street to built area will be much too high, and density will suffer.  This pattern is reflected is most all organic city growth, where blocks are commonly around 100 feet across, and rarely more than 200. 

Beaucaire, France: narrow streets and narrow blocks.