Posts about Street Grids

Archetypal Spanish house.

In the northerly climates, it's important to let in light, so buildings tend to have tall windows, but they also need to deal with cold winters. Therefore, having a tall building is an advantage, as heat is retained through the stacking of floors. Keeping the lots small, narrow and nestled together helps retain heat.

These important factors explain why lots are the sizes they are. A city in the northern European tradition will have taller and narrower buildings. Lots would be relatively shallow, with a depth of only about 35' or so for the main block including requisite garden space. With these smaller lots, the block size could be relatively small as well.

Ideal block in Alexandria, Virginia: 350' x 450'

Looking at Alexandria, Virginia as an example, we see a more "southerly" northern house, having a main block of 35 feet or so with a small wing attached and a small garden behind. The lots in Alexandria are slightly deeper because of this side wing but still relatively shallow compared to the massive blocks you find in old Spanish colonial cities.

Archtypical Alexandria house.

San Buenaventura, (aka Ventura), California, where I lived for two years, has lots 400 feet by 400 feet, four times the size of Portland's blocks. Ventura was laid out according to the needs of a hot sunny climate. Like other buildings of the Spanish Colonial era, it has low, sprawling houses. This requires a lot more ground space, and so the lots need to be significantly deeper to allow room for a usable garden behind.

Ideal block in Ventura: 400' x 400'

Pre-industrial cities needed gardens to grow produce and even raise small livestock. Almost all food had to be raised locally, so having a garden was essential to city living. After the Industrial Revolution, with the advent of fast travel, food could be brought to market from distant lands, so the importance of a garden began to wane. Thus we can see why Portland, founded in the latter part of the 19th century, could afford to have relatively tiny blocks.

The industrial city becomes less and less subject to the necessities of the environment, and so most American cities west of the Appalachians have block sizes of more or less arbitrary sizes. Anchorage could afford to have a big block size just as much as it could have a smaller one.

Today, with the advent of cars and air conditioning, the size and shape of a lot has more to do with the needs of the car and its parking than any other concern. Lot sizes revolve less around depth, and more around width, being in multiples of car widths for the garage.

Exploring these grid proportions messed with my preconceptions. I assumed the more western and newer cities would have larger grids than the more eastern and older cities, but no obvious pattern is discernible to me. Mobile, AL, settled by French colonists in the early 18th century, Tulsa, OK, a 19th century farming town, and Anchorage, AK, a 20th century frontier town, all share the same 300' x 300' internal block (street widths vary a little). What compelled the early settlers of these towns to choose, say, 220' over 440' lengths? I can't say I have any idea right now.

Manhattan is also a curious story. According to Witold Rybczynski, the expanding nation unequivocally chose the 1811 Commissioner's Grid of New York City over L'Enfant's baroque-influenced plan for Washington, DC as the model for new towns. While this is surely true, it begs the question: why are New York's long and skinny blocks not found anywhere else in the country? You would think at least one group of western settlers would seek to emulate their home town of New York more exactly.

I'm leaving aside the interesting value questions around block size. Ever since Jacobs, conventional wisdom has held that smaller blocks are preferable for walkability, but urban designer Fannis Grammenos challenges the grid somewhat in a Planetizen post.

Crossposted on Discovering Urbanism.