by
Adam Bond, Architectural Preservationist
Small Lots, Mixed Use Planning
The post-war American planning experiment in single-use zoning, lot consolidation, and large-scale development has now had seventy years to demonstrate its outcomes. The demonstration has not been favorable. Cities that restructured themselves around these principles — clearing mixed-use neighborhood fabric for highways, consolidating fine-grained lots into superblocks, separating residential from commercial and industrial use by regulatory fiat — have produced built environments that are economically fragile, socially segregated, environmentally wasteful, and physically deteriorating on a cycle that produces repeated demands for public investment to address the consequences of the original design choices.
The economic resilience argument for fine-grained lot structure — the argument that small lots distributed among many owners are more resilient to economic shocks than consolidated lots owned by fewer entities — has been developed most rigorously by the Strong Towns organization and its academic collaborators, and it rests on a straightforward principle from risk theory: distributed systems fail locally while consolidated systems fail systemically. A block of 20 row houses owned by 20 different people is a block on which any individual failure — one owner’s bankruptcy, one property’s deterioration, one vacancy — is isolated and bounded. The adjacent 19 properties are unaffected. The block’s character, its tax base, and its neighborhood function continue.
The same block of land consolidated into a single 20-unit apartment building owned by one entity concentrates all of these risks. A single overleveraged investor, a single mechanical failure, a single market shift can compromise all 20 units simultaneously. The post-war public housing projects whose demolition has cost tens of billions of public dollars since the 1990s — the Cabrini-Greens, the Pruitt-Igoes, the Robert Taylor Homes — were not architectural failures in the narrow sense. They were structural failures: buildings whose size, design, and ownership concentration created conditions under which individual problem-solving was impossible and systemic deterioration was inevitable once the level of public subsidy required to maintain them was withdrawn. Housing authorities have demolished over 200,000 such units since the mid-1990s, according to Planetizen’s 2024 analysis, destroying the housing stock precisely because the consolidated model failed — and failing, in many cases, to provide equivalent replacement units for the residents displaced.
The Strong Towns analysis extends this resilience argument to the fiscal dimension. Large-scale consolidated development — the suburban strip, the block-scaled mixed-use project, the big box retail complex — generates high tax revenue per acre in its early years but imposes infrastructure maintenance liabilities that far exceed that revenue over the full lifecycle of the development. The fine-grained, incrementally developed historic urban fabric, by contrast, generates modest but stable tax revenue with infrastructure maintenance costs that are spread over many properties and many years, producing a more sustainable fiscal relationship between development and public infrastructure. The fiscal insolvency of American suburban development is not a bug in the system. It is a design feature of a development model that was never expected to pay for itself over its full lifecycle.
The separation of residential from commercial and industrial uses — the foundational move of postwar zoning — was not a politically neutral act. As historians of American planning including Richard Rothstein (The Color of Law, 2017) and Robert Fogelson (Bourgeois Nightmares, 2005) have documented, single-family zoning was adopted in American cities in the early and mid-20th century not merely to separate incompatible land uses but specifically to maintain racial and class segregation in residential neighborhoods. The separation of uses had the secondary effect of separating access to commercial services by income and car ownership — an effect that was tolerable to the automobile-owning majority and devastating to the car-free minority.
The consequences of this separation for low-income households have been extensively documented by transportation researchers. Families in the lowest income quintile spend approximately 42 percent of their household income on transportation, according to Smart Growth America’s analysis of American Community Survey data — more than twice the proportion spent by middle-income households. This disparity is directly related to the land use patterns that make car ownership necessary: when daily goods and services are accessible only by car, households that cannot afford cars are compelled to spend a disproportionate share of their income on vehicle ownership and operation, or to go without. In Allentown, where median household income places many families in financial contexts where the full annual cost of car ownership (AAA estimated $10,728 in 2023) represents a very significant fraction of take-home pay, this is not a marginal equity concern.
The restoration of as-of-right mixed-use zoning — the permission to operate a small commercial use in a ground-floor space in a residential neighborhood, without requiring a special exception or variance — directly addresses this equity problem by making daily goods and services accessible on foot. A 2024 Strong Towns analysis of what they call the “corner store” problem documented that thousands of former commercial buildings in residential neighborhoods across America’s older cities are now legally prohibited from operating as commercial establishments by zoning codes adopted decades after the buildings were constructed. The physical infrastructure for a more walkable, car-optional daily life exists in these buildings; the regulatory infrastructure prohibits its use.
PlaceEconomics’ urban vitality research has documented a consistent relationship between intact historic building fabric and small business vitality across multiple American cities. Their analysis of Nashville’s historic districts found that businesses in historic districts had significantly higher survival rates than comparable businesses in non-historic areas, and that the density of small businesses per block was higher in historic districts than in adjacent areas with newer, larger buildings. Their San Diego analysis (released in 2025) found that 40 percent of all apartment properties in that city’s historic districts are located in areas covering a small fraction of the city’s land area — demonstrating that historic districts achieve density at a human scale without requiring the consolidation and large-footprint development that historic preservation is frequently accused of blocking.
The mechanism connecting historic building fabric to small business vitality is largely explained by rent economics. Old buildings have lower structural costs: their construction debt is long retired, their energy systems may be less efficient but their structural shells require no amortization, and their smaller footprints produce smaller absolute rent obligations. The economics of small-scale commercial tenancy — the corner barbershop, the neighborhood bakery, the small law office, the independent bookstore — are viable in these smaller, lower-rent spaces and unviable in the newly constructed large-format commercial spaces whose high construction costs require high rent to service. Jane Jacobs made this argument in The Death and Life of Great American Cities in 1961, and the empirical research of the intervening sixty years has not refuted it. Historic buildings are not merely culturally important; they are economically necessary for the small-scale commercial ecology that makes urban neighborhoods livable.
The formal lot consolidation that zoning review can regulate is not the only mechanism through which the fine-grain resilience of a neighborhood’s ownership structure can be undermined. Portfolio landlordism — the acquisition of large numbers of individual small properties by a single investment entity — produces the functional equivalent of lot consolidation without triggering any regulatory review. A portfolio investor who owns 200 row houses in Allentown makes centralized decisions about maintenance, renovation, and disposition that affect the neighborhood the way a single consolidated building owner’s decisions would, but without the transparency or accountability that attaches to a single large property.
The evidence on portfolio landlordism’s effects on neighborhood stability is mixed in aggregate but concerning in its distributional consequences. Research by the Urban Institute and the National Housing Preservation Database documents that large portfolio investors in rental housing consistently spend less on maintenance per unit than owner-occupants or small landlords, produce higher rates of code violations, and are more likely to sell or abandon properties during economic downturns, precisely the conditions under which neighborhood stability is most fragile. The concentration of rental portfolio ownership in post-industrial cities like Allentown — where property values and rents are lower, making portfolio acquisition financially attractive to investors seeking yield — creates conditions of structural vulnerability that are invisible in standard planning data because they do not involve changes to the physical lot structure that zoning regulations track.
Marohn, Charles L. Jr. Strong Towns: A Bottom-Up Revolution to Rebuild American Prosperity. Hoboken: Wiley, 2019.
Rothstein, Richard. The Color of Law: A Forgotten History of How Our Government Segregated America. New York: Liveright, 2017.
Fogelson, Robert M. Bourgeois Nightmares: Suburbia, 1870–1930. New Haven: Yale University Press, 2005.
Planetizen. ‘Good As New: The Vital Role of Preservation in Solving the Housing Crisis.’ Planetizen Features, November 2024.
Lincoln Institute of Land Policy. What Makes Mixed-Use Development Economically Successful? Cambridge: Lincoln Institute, 2012.
PlaceEconomics. Reasons Historic Preservation Is Good for Your Community. City Studies Working Paper. Washington: PlaceEconomics, 2020.
Urban Institute and National Housing Preservation Database. Preserving, Protecting, and Building Climate-Resilient Affordable Housing. Washington: Urban Institute, 2024.