Sweet Spot Density for Livable Neighborhoods

Single-family detached homes typically epitomize sprawl, while 4 or 5 story apartment buildings now seem to be the utopian ideal for livable neighborhoods. But some of the most livable and walkable neighborhoods I know are largely comprised of single family homes.

This is sprawl?

University Heights - Lincoln AveUniversity Heights, San Diego, CA

This is an early 20th-Century streetcar suburb lined with craftsman homes (many of which have in-law units in back) interspersed with row houses and smaller apartment buildings. Located within blocks of traditional business districts, the neighborhood has well-maintained sidewalks and service alleyways throughout. University Heights and the surrounding neighborhoods are urban in character, with multi-story dwellings clustered closer to commercial streets. Motor vehicle traffic is typically quite low; pedestrians and bicyclists abound. Open space could be better, though the neighborhood has its own park and is only a mile from Balboa Park - a large urban park.

There is an overall feeling of serenity and adequate breathing space.

This type of residential arrangement is seen in small cities and towns throughout the country, as well as the first-ring suburbs of many metropolitan areas. Transit is often a missing link in these older areas; in most cases, rail and streetcars are long gone.

But this is not sprawl?

Fenton Parkway, San Diego, CAFenton Parkway

This is the sort of cookie cutter housing that is popping up all over Southern California. It is high-density, autocentric suburban. Although these subdivisions are placed near transit and shopping (i.e., malls), many are logistically disconnected from these services. Car density seems to be at least as high as housing density. Functional park space and public open space are near zero, as much of the land is designated for housing and car storage.

The feeling is congested and claustrophobic.

Many of the problems associated with neighborhood #2 stem from its car-oriented framework and a serious lack of park space. If people are going to live in stacked apartments, sufficient space for outdoor recreation is essential, as is a safe framework for walking and biking.

In my experience, authentic neighborhoods like University Heights are some of the most walkable in the country, although inadequate foot traffic at night can be a safety concern on purely residential streets. Even without rail, these areas provide access and mobility because they are both centrally-located and designed for pedestrians.

So, which neighborhood density is the most livable? At what point is quality of life reduced due to overcrowding? Or does it all come down to good neighborhood design?

Diana DeRubertis is an environmental writer focusing on the urban planning field.



Ideal density? 20 units per acre minimum.

A walkable neighborhood requires a full-service grocery store. Otherwise the neighborhood is not truly walkable; some services must be accessed by car or by mass transit if a full service grocery store is not within walking distance.

A full-service grocery store requires a minimum population of 15,000 people on average. (http://ci.emeryville.ca.us/archive/General_Plan_Update_Steering_Committe...) also: (http://www.epa.gov/dced/density.htm)

Maximum comfortable walking distance is 1/2 mile, or a 10 minute walk at a moderate pace.

So, we have an area that is one mile in diameter with the grocery store in the center. 15,000 people must live in this area to support the store. Therefore the required density is 15,000 people per square mile. This translates to roughly 20 units per acre, if half of the land is zoned residential. (4 to 5 units per acre translates to roughly 3,000 - 4,000 people per square mile - assuming 320 acres used for residential and 2.5 people per dwelling unit) With 20 units/acre, full-service stores can be spaced out in one mile intervals in every direction, so that the maximum distance to a store at any point in the city is 1/2 mile.

If you reduce the density to 10 units per acre, than full-service grocery stores can only be located in 2 mile intervals. This means that a good 50% of the population is going to be beyond walking distance of the store.

20 units per acre excludes the possibility of detached, suburban homes - even the small craftsman homes. Units must be attached like townhouses or apartments.

To conclude, a walkable city requires full service grocery stores spaced out in one mile intervals (or less) in every direction. This requires a minimum density of 20 units/acre or 15,000 people/sq. mi.

20 units/acre can be easily achieved with attached units in buildings no taller than 2 stories, with plenty of room for courtyards and green spaces.

I am not sympathetic to people's desires for more space and more stuff - this is what is killing the planet. We must build cities in line with what nature and reality can reasonably offer us. People have lived happily without backyards for thousands of years - backyards are a recent invention. People can learn to live without them again and will be just fine.


Full Service Grocery

I don't know what Emeryville means by a full-service grocery store, but Emeryville does have a Trader Joes, and it is possible to shop for groceries exclusively at Trader Joes.

I myself shop at the Emeryville Trader Joes and at a 1950s grocery store in Berkeley of about the same size (about 10,000 sq ft), which worked perfectly well for family shopping during the 1950s, when families were bigger than they are now.

By full-service grocery store, I expect they mean 25,000 to 60,000 sq ft, and stores of that size appeared only when they could appeal to people who drive to go shopping.

The fastest growing segment of the grocery industry is stores of about 10,000 sq ft, such as Tesco's Fresh and Easy - which is doing so well that Wal-Mart has announced that they are about to start opening grocery stores of that size.

Needless to say, the streetcar suburb described in this post had small grocery stores when it was built. At the time, I expect there was not a single retail grocery store of 25,000 sq ft in the world. In your words, people lived happily without 25,000 sq ft supermarkets for thousands of years.

(Note that I am just commenting about the Emeryville doc you link to, not about the main point of your post. For background on my feelings about Emeryville, see http://preservenet.blogspot.com/2006/03/walking-to-lunch-in-emeryville.html )

Charles Siegel

Begging the Question

"This begs the question – which neighborhood density is the most livable?"

You mean that it raises the question. For the correct use of "begging the question," see http://en.wikipedia.org/wiki/Begging_the_question

Charles Siegel



Livable Neighborhoods

Yes, it comes down to good neighborhood design. And good pedestrian street design. And good building design that works well with the good street design.

Michael Lewyn's picture

all of you are right

Design matters.
But density matters too.
And so does diversity [of land uses].
So for maximum walkability, you need all three- density, diversity and design.
If you have one or two of them- well, you're still ahead of most of America.

Great Post

Great post. It seems like often times developers and cities try to create livable, walkable, communities by increasing the density with no regard to the most basic design principles. Density, without proper design and mixed use zoning can create places that are worse than the low-density suburbs many places are now trying to avoid.


"Needless to say, the

"Needless to say, the streetcar suburb described in this post had small grocery stores when it was built. At the time, I expect there was not a single retail grocery store of 25,000 sq ft in the world. In your words, people lived happily without 25,000 sq ft supermarkets for thousands of years."

Yes, but they had the equivalent of large stores - markets where you could obtain everything you needed. The city was small enough that everyone was within walking distance of these markets. In a streetcar suburb like the one described the density isn't high enough to support all the services required by a person within a small enough area so that everything can be walked to. Some services are going to be beyond walking distance which is where the streetcar comes into play. A truly walkable city, in my opinion, is one in which not even streetcars are necessary. A walking city has a higher minimum density than a streetcar suburb.

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