The Atlas of ReUrbanism begins to explore how older buildings help density and affordability, but it doesn’t go far enough.

Houston’s got character. (Atlas of ReUrbanism)

Is historic preservation a friend or foe of affordability? That depends on where you’re looking.

Creating special districts of antique homes in the name of “character” can block access to schools, amenities, and property values for those who can’t pay the cost of entry. And suppressing new development in certain neighborhoods limits the potential for tall, dense buildings that can accommodate the most people at the lowest prices, many urban economists say.

But many preservationists will strike back at that assessment, claiming that these older neighborhoods tend to be much more dense than newer ones—and that developers who create housing and commercial space out of existing buildings often pass on lower costs to tenants than those who raze and rebuild.

A new set of maps from the National Trust for Historic Preservation contributes a data-driven perspective to this complex issue. The Atlas of ReUrbanism charts 50 U.S. cities by the “character” of their building stock. That’s a charged word in urbanist circles; here, “character” is an equally weighted measure of the median age of buildings, the diversity of age of the buildings, and the size of buildings and parcels, according to an accompanying report. What’s revealing is how the geography of “high-character” blocks—where the building stock is mostly smaller, older, but also mixed in age—intersects with affordability and density, as measured by Census data. Older stock “serves as unsubsidized, ‘naturally’ affordable housing,” the report’s authors writes.

According to them, high-character blocks tend to have higher shares and numbers of affordable units of rental housing, compared to low-scoring blocks. “In many cities in the Atlas, there is twice the number of affordable rental housing units on blocks with older, smaller, mixed-age buildings,” the authors write. The report also states that density, in terms of both population and housing units, tends to be higher on “high-character” blocks.

The Roxborough area of Philadelphia, mapped by “character.” (Atlas of ReUrbanism)

Maybe that’s not surprising; you’d expect for older, denser areas near downtowns to have higher character scores, while newer, less dense neighborhoods on the outskirts would score lower. In the five cities that are fully mapped in the Atlas—Chicago, New York, Philadelphia, Houston and Los Angeles—that pattern mainly holds true. But playing with the layers of data in the interactive maps offers some fresh observations on where character is and is not. Kyle Shelton, an urban historian at the Kinder Institute of Urban Research at Rice University, toggled around with Philadelphia’s character scores, and writes this on the Urban Edge blog:

In Philadelphia, Character Scores illustrate that older, non-central residential communities have become surrounded by newer, often lower-density development. Roxborough, to the northwest of downtown, possesses a high Character Score, as much of its historic built environment persists. But the surrounding areas have lower Character Scores, suggesting a very different development pattern.

Shelton also notes that Chicago’s inner Loop is surprisingly low-scoring, while residential neighborhoods to the north and south score much higher.

Unfortunately, the interactive maps don’t let you layer on the number of affordable housing units per block—you’re left to take the analysis of the report, plus city-specific fact sheets that drill into some extra detail, at face value. The report does include an interesting chart that compares character and density (below), which might be interesting to folks who see new construction as the only answer to increasing densities. Rather than look at historic buildings as targets for tear-downs, why not look first at the vacant space within them? Furthermore, the authors write, “how much additional development capacity could be realized if surface parking lots were replaced by housing, office space, and retail?”

(Atlas of ReUrbanism)

The report also connects the high densities and affordability of “high character” blocks to diversity. Nearly two-thirds of the 24 million Americans of color who live in the 50 cities in the Atlas of ReUrbanism “live in high Character Score areas—nearly 75 percent more than in areas with large, new buildings,” the report states. The authors also found roughly “108,000 women and minority-owned businesses on blocks with older, smaller, mixed-age buildings” nationwide. That was “40,000 more than the number found in areas characterized by large, new buildings.”

Remember that in these terms, a “high character” block is one with buildings that are mostly smaller and older, but are also mixed in age. By this metric, most neighborhoods in these mapped cities have strong character scores. It’s helpful and unhelpful to use such a wide paintbrush. The conversation about preservation, density, and affordability should be more than about making special districts out of picture-perfect Queen Annes or well-kempt downtown cores. This report suggests there’s value in old(ish) neighborhoods all over the map.

On the other hand, if preserving old buildings can help boost affordability and density, it’d be helpful to know where, specifically, they’re doing that. Protecting a high-density, lower-income neighborhood with 50-year-old housing stock from, say, an aggressive condo developer could help protect affordability in a city with a white-hot housing market. Roping off a special district of lacy Victorians may not. Here’s hoping a future iteration of these maps goes deeper.

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