Monday, July 18, 2011

New World Economics on Single-Family Solutions

Nathan Lewis' latest is now available: How to Make a Pile of Dough with the Traditional City 4: More SFDR/SFAR SolutionsNathan addresses the very basics of urban form: the relationship of block depth to street width, lot dimensions, and accommodating cars into a dense urban fabric.  Feel free to leave comments about it here.

One underlying point is similar to the one I made in last week's A Tale of Two Densities: to create a neighborhood that is both 1) mainly single-family, attached or detached, and 2) is dense enough for walkability, blocks must be shallow, and if blocks are shallow, streets must also be narrow, or else the ratio of street to built area will be much too high, and density will suffer.  This pattern is reflected is most all organic city growth, where blocks are commonly around 100 feet across, and rarely more than 200. 
Beaucaire, France: narrow streets and narrow blocks.

14 comments:

  1. It's a great idea, but getting it implemented would pretty much require hiring the Mafia to assassinate every traffic/road engineer in the developed world. They set minimum standards for roads which are completely incompatible with the idea of urban density.

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  2. I could not agree more with Nathan's article and I am grateful for the plethora of examples provided. It is quite clear to me that this type of development is necessary for our residential neighbourhoods, the question that bothers me is how do we retroactively fix the development patterns that already exist? Or do we even bother?

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  3. Will somebody please convince Nathan Lewis to get a blog??

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  4. Anonymous: connected developers *are* the mob in the modern day. They can usually get all sorts of crazy projects approved by the city, because they are a part of the political machine that gets people elected.

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  5. Not sure why Nathan's saying that 40*50 feet is better for windows than 25*80. If you want window placement, you want a larger perimeter-to-area ratio, not a smaller one. Manhattan lots are traditionally 20*100 and even then narrow buildings have to have slightly inefficient shapes in order to allow window access to every room, and wider buildings than 20' have very weird shapes, like the letters E or H (e.g. look at the Waldorf Astoria on Google Earth).

    The advantage of having very short blocks with very narrow streets is exactly that it allows cutting the block in half, increasing perimeter to area ratio. In other words, instead of having one 20*100 building with two apartments per floor, it's possible to have 20*40 with one apartment per floor, and part of the space that's wasted on the extra street can be reclaimed in building shapes that use the entire lot. See for example any Manhattan block with small buildings; there will generally be a no man's land between the two rows of buildings, which could be used as an extra street (121.5th, 122.5th, etc.) but for the fact that there's a continuous line of buildings along the avenues.

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  6. Alon,

    40*50 is better than 25*80 in Nathan's post, for 2 reasons:

    1) The wider (50 ft) street frontage lets you put in a garage right agains the very narrow street, without having the garage door totally dominate the front of the house. (With 25 foot lots, with 10 foot garages, almost half of the street is garage doors on each side). This is nice if you want to allow off-street parking but still make a walkable, high-density neighborhood with narrow streets.

    2) If built as townhouses (with shared walls on each side), the 50 foot lot has twice as much room for windows (on the street and rear face) per house as the 25 foot, deeper lot.

    If you want a 20 foot wide house you could have windows on all 4 sides in the narrow lot... but you will be just 5 feet from your neighbors, and 20 feet is really narrow (now the garage is over 1/2 of the house in front!). With a 50 foot lot, you can have a 40 foot wide house with windows on all sides, a small backyard, and 10 feet of room in between each house - just perfect for parking a couple of cars off-street, if that's what you want.

    You can't do that with 80 foot deep lots, if you want the same square footage.

    And of course, with 40 foot deep lots, you can make even smaller houses (say 1000 square feet) on a 25 x 40 foot lot pattern, for even better affordability, and even higher density.

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  7. I've been considering making a blog for Nathan. I would just steal his posts, every time he writes a new article, and turn them into blog format. In between, I could post his older articles, to catch new readers up. It would be great!

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  8. Hi Joseph,

    Charles has agreed to repost my items here. This works well because:

    a) Now we have a nice single location for "old urbanism" topics.
    b) My posts are very long, with many photos, not suitable for the typical blog format
    c) There is typically only about one per month.
    d) I wanted to have a format that was more permanent, while blog content tends to be considered "disposable."
    e) I had a forum on my site for a while, but nobody participated.
    f) When people do participate, most of the comments are junk. I have a friend with a blog that used to get hundreds of comments per item, but he ended up eliminating the comment option because of too much junk.

    Thanks for being so supportive. What we really need is another person -- like yourself -- who has their own ideas about "old urbanism." Charles has produced a huge amount of new material, which has its own "Charles Gardner" character, which has added a lot to the overall discussion.

    This is a great time to be an "old urbanist" because there is virtually no competition.

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  9. Joseph,

    In New York, those 20*100 lots host two apartments per floor - one front, one back. There are no garages because the buildings predate the car. People who are anxious to own a car park on the street and move their cars twice a week, or pay for monthly parking at a commercial garage.

    The distance to the next building over is an issue, yeah. It's an opposite force to window frontage, because it's optimized when the area-to-perimeter ratio is high. The compromise between the two used in Manhattan and Brownstone Brooklyn is that the buildings are usually not actually rowhouses, but just look that way from the street; further back, there's a distance of about 5-8 feet between successive buildings. Larger buildings, especially ones large enough to require H or E shapes to guarantee sufficient window coverage, have larger gaps - about 10-15 feet.

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  10. Alon: one of the things I discovered while reading up on the 1811 Commissioners' plan was that the New York legislature, which empowered the Commission, had made two requirements of the plan: 1) that no street be narrower than 50 feet, and 2) that no block subsequently be subdivided by new public streets (except by legislative act, as was required for Lexington and Madison Avenues).

    It seems reasonable to suppose New York's pattern of fairly narrow, very long blocks was a reaction to these rather severe constraints. Blocks wider than 200' would end up having large amounts of inaccessible space in their centers, since the alleys that broke up large blocks in Philadelphia, Baltimore, Washington, etc., could not be built except by legislative act. Narrower blocks, on the other hand, were doomed by the street width requirements -- at 150' wide or less, streets would approach 50% of the city area, assuming sufficient N-S avenues. At 200', though, as you note, there is still a "no-man's land" in between buildings, indicating a better match might have been 150' wide blocks with something like 35' cross streets -- if that had been an option for the Commissioners.

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  11. What some tenement owners did in the late 19th century in response to the 200' block size was build two buildings on one lot, one behind the other. The emerging urban renewal czars absolutely hated those, and to them they were one of multiple problems that required large-scale slum clearance.

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  12. Do 16 ft wide streets exist anywhere in America in an extensive enough format for living? Are they even legal anywhere near the suburbs?

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