Ryan Avent, writing at Architect Magazine, takes a look at the recently floated idea of putting a Redskins practice facility at Reservation 13 in DC.  One of the reasons for the backlash against the idea was the opportunity cost of a metro-adjacent, develop-able site (a scarce enough commodity in DC) lying fallow for the purposes of football practices. Regardless of the merits of that particular idea, Avent notes that denser development all around creates more capacity for these kinds of public goods.

Consciously, in the case of urbanists opposed to the practice facility, or unconsciously, as is likely to be true of nearby residents, opponents are expressing an awareness of the importance of density to urban life. To make Reservation 13 come alive, there must be people there—enough of them to support local businesses such as coffee shops and corner stores. With sufficient critical mass, the neighborhood might support restaurants, bars, and shops, which could then draw residents from other corners of the city. A healthy density helps integrate a neighborhood into the broader city, which then reinforces that neighborhood’s local amenities. Were more than half of the parcel dedicated to a relatively stultifying land use, critical density might fall out of reach.

Lurking within this compelling argument, however, is an unjustified assumption. On its own, the use of 33 acres for football need not reduce the parcel’s density. Development proposed for the remaining land could simply be made taller. In the 2003 master plan, the city recommends building heights of two stories on the western, neighborhood-facing side of the property, rising to 10 stories on the waterfront side (the property slopes downward toward the water). In practice, the only thing preventing Washington from having its cake and eating it too is a devotion to short buildings.

Not only in terms of opportunity costs for limited parcels of land, there’s also the matter of revenue.  Constraints on development limit the ability to ask for public amenities, ranging from new infrastructure to affordable housing via inclusionary zoning.  There’s only so much juice that can be squeezed from the orange.

Indeed, the core urban logic of density is taking root (“Height in this city isn’t about height. It’s about density,” Hickok said). While a great deal of the discussion has focused on changing the height limit, there’s a lot of potential capacity between the more restrictive zoning and the federal height limit. Avent continues:

Indeed, the scarcity of land that has so energized residents to question the mayor’s efforts is entirely a product of the District’s laws and regulations. The neighborhoods just west of Reservation 13, like much of the city’s residential land, are zoned R-4. This allows for matter-of-right development of single-family homes on lots with minimum specified widths and maximum specified heights. If Washington wanted to do so, it could substantially increase the available developable area. A zoning area that doubled the District’s population density—essentially creating an entire second city on top of the first—would be achievable without so much as questioning the city’s statutory height limit—and leaving the District at less than a third of the population density of Manhattan.

Utilizing modest-in-appearance, yet substantial increases in density amongst DC’s residential areas (mentioned here), we could greatly increase the effective overall density of the District.  But those small interventions (alley dwellings, english basements, etc) won’t produce that ‘second city’ that Avent discuses.  That would require more intense development.

Writing in Crosscut, Ed McMahon discusses some of those forms:

Julie Campoli and Alex MacLean’s book Visualizing Density vividly illustrates that we can achieve tremendous density without high-rises. They point out that before elevators were invented, two- to four- story “walk-ups” were common in cities and towns throughout America. Constructing a block of these type of buildings could achieve a density of anywhere from 20 to 80 units an acre.

Mid-rise buildings ranging from 5 to 12 stories can create even higher density neighborhoods in urban settings, where buildings cover most of the block. Campoli and McLean point to Seattle where mid-rise buildings achieve densities ranging from 50 to 100 units per acre, extraordinarily high by U.S. standards.

The challenge, however, is meshing that modestly tall kind of density (respectful of the federal height limit) with the current structures on the ground.  It would require large scale redevelopment of already extant neighborhoods.  Indeed, some of those structures that DC does have are threatened by the lure of development potential. This manse on K St is one of the last of its kind.

The irony is that the constraint on height (and thus density) in DC is one of the key reasons legacy lowrise structures are under such development pressure.

Google Streetview - Northeast corner of 6th Ave and 38th St

A quick stroll around Midtown Manhattan will reveal lots of really tall buildings, both old and new.  But there are also lots of small and short structures mixed in – since development pressures have the ability to go up (not that New York is free of development constraints – see Ed Glaeser), they don’t have to knock down all smaller structures as a matter of course.

Google Streetview - Southwest corner of 6th Ave and 38th St

The takeaway is about tradeoffs – preserving structures like the remaining manse on K St is a constraint.  It can be a workable constraint, depending on what other constraints are also in place.  But the combinations of affordable housing, historic preservation, a flat skyline, shorter buildings and smaller scale development might not be feasible together.

McMahon’s larger point is one of context – simply plopping a skyscraper down amidst a sea of shorter buildings is a recipe for another Tour Montparnasse.  But context is relative and probably speaks more to the pace and evolution of the change than to the nature of the change itself.  Likewise, additional height might be the very thing that helps preserve the small-lot fabric of a place while still providing a release valve for growth, as it has in many locations in Manhattan.

Avent concludes with a cautionary note about the costs of these preferences:

What the battle over Reservation 13 makes clear, however, is that Washington’s height aversion crowds out attractive amenities—a football facility in this case; parks or museums in others; willing would-be residents, artists, entrepreneurs, and taxpayers in many, many others. It has a substantial cost, in other words.

As mentioned above, this is really a discussion about trade-offs.  Paris is often mentioned as a fellow flatly-skylined city with far greater density than the District today. But would DC residents really embrace the intensity of redevelopment required to turn rowhouse neighborhoods into 5-6 story walk-up neighborhoods?  If not that particular trade-off, then what other trade-offs are on the table?

Should be an interesting conversation.