Towards a More Nuanced Understanding of Density

Arguing for the value of historic low and mid-rise, but also dense, areas of Brooklyn, Washington D.C., and New Orleans, Edward T. McMahon asks us to reconsider the pursuit of density as an end in itself, and the high-rise as its fullest expression.

As the land development pendulum swings back towards higher density development, from the low-density patterns of suburban sprawl, McMahon questions the common assumption made by developers and urban planners alike: "that density requires high rises: the taller, the better." Citing examples of cities and neighborhoods that achieve high levels of density without resorting to high-rises, and exhibit walkable human-scaled street level environments (which high-rises often do not), McMahon argues that, "we do not need to build thousands of look-a-like glass and steel skyscrapers to accomplish the goals of smart growth or sustainable development."

The recent debate about increasing height limits in Washington D.C. is just one example of a global struggle between "those who want to preserve neighborhood integrity and those who want Trump towers and "starchitect" skyscrapers."

"I love the skylines of New York, Chicago and many other high-rise cities. But I also love the skylines of Washington, Charleston, Savannah, Prague, Edinburgh, Rome and other historic mid- and low-rise cities. It would be a tragedy to turn all of these remarkable places into tower cities," writes McMahon. 

Full Story: Density Without High-Rises?



Michael Lewyn's picture

2 issues with the argument

1. McMahon writes that "many of America’s finest and most valuable neighborhoods achieve density without high rises. Georgetown in Washington, Park Slope in Brooklyn, the Fan in Richmond, and the French Quarter in New Orleans are all compact, walkable, charming — and low rise." These are all primarily residential and small-scale commercial areas. But major downtown business districts tend to have a significant number of high rises. Does this fact suggest that even if a city does not need high rises for residential density, it might need high rises to keep business in the city?

2. The most compact cities (New York, Chicago, etc.) aren't primarily high-rise- but they do contain high rise districts. So why shouldn't Washington have at least a few areas with taller buildings?

Try Comparing Cities

The way to answer question 1 would be to look at the mid-rise cities that McMahon cites, such as Prague and Rome, and see if they have more trouble keeping businesses than high-rise cities, all else being equal.

I don't see any reason to believe that they do. I haven't heard that these mid-rise cities have been declining economically.

Charles Siegel

Michael Lewyn's picture

Don't think Prague and Rome are comparable to bigger cities

Prague and Rome don't face the level of competition that American cities do; they are in smaller countries and (I suspect) have somewhat fewer issues with more permissive suburbs.

Think of height limits as basically limits on occupancy: imagine that you had a law saying "no business can have more than 100 employees" or "no apartment building can have more than 100 occupants." Wouldn't those limits have a market-distorting affect?

Height Limits and Occupancy Limits

Prague and Rome are in the EU, an economy that has a larger population than the US. They may well have fewer issues with permissive suburbs, but I know you agree with me that the US also should have more regional planning and be less permissive about suburban growth.

Your two examples of occupancy limits seem very different to me.

If we said that no apartment building may have more than 100 occupants, I think developers would build smaller apartment buildings but build more of them. The total number of apartments would probably not be affected significantly. There would be a market distorting effect, but (in my opinion) it would be for the better: I would rather live in a traditional city with many moderate size apartment buildings than in a modern city with fewer huge high-rises. I think it would be better both esthetically and socially.

If we said that no business can have more than 100 employees, it would obviously prevent a modern economy from functioning, but a height limit does not do anything like that. A large business can build a complex of six-story buildings rather than one highrise. In fact, most silicon valley businesses, including huge companies, have offices in this sort of complex, and that is one of the most dynamic and modern sectors of our economy.

Note that you can actually get higher density per acre with mid-rise buildings and traditional urban form than you can with high-rise tower-in-a-park urban designs, as I pointed out in an earlier comment about Paris.

Charles Siegel

Michael Lewyn's picture

they'll build, but not where you want them to build

Perhaps in a world where there were no suburbs (or, in the case of the EU, more permissive countries) to go to, or no NIMBYs limiting infill, height limits could lead to a low-rise utopia. But in the real world, I doubt it.

For example, a developer might build smaller apartment buildings rather than a few large ones. But to do that, they are usually going to have to get more land than they would for a high-rise. Where can they get land more easily? Suburbs where land is cheap and abundant, and where there are fewer NIMBYs to object.

Similarly, a business that wants to build a "complex of six-story buildings" is not going to be able to do that in an urban core. Instead, they will go to a suburban office park where there's lots of land.

We know this through the example of the District of Columbia (the only U.S. city with height limits). Although the D.C. region has been a growing region throughout the entire 20th century, the District's own population profile looks like that of a Rust Belt city: massive declines throughout the 1950s-1990s, with the first population rebound coming in 2000-10.

If D.C.'s growth had been typical of that of other fast-growing metropolitan regions, it would probably look like New York or San Francisco or Boston: population losses in the 1950s-70s, but population would have started to rebound as early as the 1980s. (Having said that, I realize that there are other significant differences between D.C.. and other cities- but I suspect that height limits might be a factor too).

Where and How I Want them to Build

I don't mind their building in the suburbs, if they build in urban style.

For example, there is not enough room in San Francisco for all of Silicon Valley, no matter how tall the office buildings. It would have been fine for them to build those 5-story headquarters complexes in San Jose and the penninsula, if 1) the new buildings had clustered around rail stops instead of around freeway exits and 2) the new buildings had been built around a walkable street grid instead of in superblocks surrounded by arterial streets. San Francisco could have kept its human scale; I think it was much more attractive before the modern wave of highrises. And we could have built more cities in the region on the same human scale. So what is the problem?

For smart growth, you have to build enough density to make it possible to walk, but the examples of European cities show very clearly that you can do this with a 5-story to 7-story height limit. Apart from density, the issues are building rail and other forms of public transit rather than freeways and building walkable street grids rather than suburban street systems. You can have auto-dependent cities filled with highrises if you don't follow these two principles.

Charles Siegel

Michael Lewyn's picture

maybe in some alternate universe

Maybe in the alternate universe where suburban jobs are all at pedestrian-friendly rail stops, it might be "fine" to let big businesses move to San Jose and the suburbs (though I'm not even sure about that- a region where jobs are that far apart is going to be more car-dependent even if the jobs are served by rail, since the rail commutes might be too long to be feasible for many).

But in the universe we actually live in (where suburban locations usually mean sprawling office parks with no sidewalks and minimal transit) I think attacking urban high-rises is an example of "letting the best be the enemy of the good."

Universe of energy descent.

I'm all for density, but in a less energy-dense world, high-rises with their reliance on energy for moving in the building and their leaky envelopes are likely going to be a liability, not a salvation. I continue to be fascinated that high-rises are offered as a solution. Maybe in a world with half the population we have today that has maintained order...



Highrises as Energy Gluttons

Good point, and one that Michael Mehaffy made at length at

Charles Siegel

Michael Lewyn's picture

Looking more carefully...

I'm not going to try to win an argument about energy, since it involves scientific expertise that I don't have. A few points though:

1. just from looking at the abstracts, most of the concerns were about 40+ (or at least 20+ story) buildings. The number of residential buildings that high is pretty small. When we're discussing residential buildings, the real argument is about whether to permit 10-20 story buildings or to make everyone choose between the incredibly limited menu of single family homes and 5-7 story buildings.

2. As far as commercial buildings, I wonder whether NYC's residential densities could work without the skyscraper densities of the major commercial areas. It seems to me that a transit-oriented city works well if there is a very centralized skyscraper business district as in NYC. But if you have dozens of medium-density hubs (at least in a NYC-size big city), I suspect that most people are going to drive to them even if they are accessible by transit, for the simple reason that a 50-unit-per-acre big city is going to sprawl out over a zillion miles.

3. The post itself notes "These cities are indeed very positive when it comes to carbon and other ecological metrics. But it's often overlooked that tall buildings are only a fraction of all structures in these places, with the bulk of neighborhoods consisting of rowhouses, low-rise apartment buildings, and other much lower structures." In other words, the notion that high-rises drive out everything else (which is at the root of a lot of anti-high rise paranoia, I think) is just rubbish.

More On Highrises

Michael, it is an interesting discusion, and I hope you don't mind if I continue for another round

1. Michael Mehaffy was countering the idea that highrises are necessarily more benign environmentally than midrises, an idea that is common among city planners because they think primarily about land use and transportation. He says that, when we consider all factors, the evidence is not in yet. There is no ecological imperative for highrises, as some people think.

2. You can get densities of about 100 per acre with midrise buildings. Doing a rough calculation, that means you can fit 1 million people in 16 square miles, a square of 4 miles by 4 miles. I think you could do wand with a region made up of cities like this, connected by rail. When you get to a city the size of New York, it is plausible that you do need highrises - but it is also plausible that there is a lower quality of life for most people.

3. I don't think the fear is that highrises drive out everything else. In part, the aversion to highrises (not really fear) has to do with urban design: you get the best urban design when you have a consistent urban fabric and when major public buildings rise above the fabric, and highrises destroy this sort of urban design. I am currently vacationing in Paris, which is a perfect example of this sort of urban design, with an urban fabric of 6 to 8-story buildings and buildings like the Pantheon, the Invalides, and so on, rising above the fabric; but the Tour Montparnasse is a blight on this urban design and doesn't fit in at all. In part, the aversion is the impersonality of the highrises: Jan Gehl has done drawings showing that there is no visual connection to the ground when you live on the higher floors, which you can see at

I think it is worthwhile to preserve urban design of the relatively few remaining examples of cities without highrises, as this article says. One Tour Montparnasse could change the character of one of these cities completely, and the starchitects of this world are doing their best to do exactly that.

Charles Siegel

Meanwhile, In Our Universe

What actually happened in our universe was that 1) they did build lots of highrise in San Francisco and 2) nevertheless, suburban office parks in Silicon Valley became the region's employment center, and the entire region became more congested and more auto-dependent.

It proves that building high-rises in one city is not the solution to the region's auto-dependency. What is needed, as I said, is regional planning that emphasizes transit over freeways and that clusters development in walkable neighborhoods around transit stops.

As you know, this is not an original idea on my part. It is the conventional wisdom among planners.

I don't think it adds anything to this conventional wisdom to insist on highrises.

Charles Siegel

Michael Lewyn's picture

By the way, there are tall buildings in Rome, Prague etc

Michael Lewyn's picture

By the way, there are high-rises in Europe

I know there are highrises in Europe

I mentioned the Tour Montparnasse in an earlier comment as an example of why high-rises are bad urban design.

Also, see my comparison of London's "gherkin" and St Pauls at for a discussion of why highrises don't work well as urban design.

Charles Siegel

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