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Density of new housing in the US is similar to China. While the 30-story towers look impressive, the 6-story buildings popping up throughout American cities are more efficient. Both have around 150 homes per acre. Thread 1/ 
How did the US and China end up building the same density so differently? In the US, height limits of wood construction, zoning, and urbanist design guidelines create buildings that fill the block. 2/
In China, buildings are made of concrete, and there is a premium for south-facing units and green space. Zoning allows taller heights, but still has density limits, and so the result is towers in the park. 3/
So, why do Chinese cities have higher population density than American ones? Suburbs. While China does build oneplexes (they call them villas), these take up a much smaller fraction of the land, vs. American cities where 75% of land being oneplex-only is typical. 4/
Same comparison, now with a typical European block added. In Europe, the buildings are concrete and are slightly taller than their US counterparts. While again the density is similar, the couple additional floors allow larger courtyards and some front yard landscaping. 5/
@foxjust at @BW just wrote a great article explaining the American type of midrise apartments. bloomberg.com/opinion/articl…. 6/
Highrise zoning (40+ floors) in Singapore, Hong Kong, San Francisco, New York, and Miami. The US cities are denser, with floor area ratios of 10-20, vs 8-10 in Singapore/HK (though bedroom density is similar due to larger rooms in the US). Details of each city in thread. 7/
The Singapore example is The Pinnacle, a 52-story public housing project near the business district. en.wikipedia.org/wiki/The_Pinna… It has a floor area ratio of 8.4 - the buildings are deceptively large since the center is hollow to allow ventilation in the tropical climate. 8/
Most HDB housing in Singapore has a floor area ratio of 2.8, due to large parking structures and lots of green space. You can view the zoning map at ura.gov.sg/maps/# , residential areas are a peach color. As 1960s buildings age, some are upzoned for redevelopment. 9/
Note the openness of the modern Singapore floorplan. Every room has windows, including the kitchen and bathrooms. There are no internal corridors, entry is from open balconies. World's tallest dingbat? :D srx.com.sg/hdb/central-ar… 10/
You'd think open air balconies 50 stories up would be vertigo inducing, however, it appears that residents biggest concern was that people would break into their unit by climbing over the balcony rails and stepping over a 400' chasm. forums.vrzone.com/chit-chatting/… 11/
Hong Kong's density tops out at a floor area ratio of 10. The illustrated example is 40 stories of one of their housing department's standard plans, the "New Harmony". Photo of 健明邨 (King Ming Estate) by Baycrest - CC BY-SA 2.5, larger version at commons.wikimedia.org/w/index.php?cu… 12/
Like in Singapore, Hong Kong also gives bathrooms & kitchens windows. The kitchen is enclosed, as stir-frying is hot and greasy, so kitchens exhaust to the outside. (US highrises typically use ducts and grease buildup can be a problem) housingauthority.gov.hk/en/global-elem… 13/
San Francisco's example is the RH-DTR Rincon Hill Downtown Residential zone. Of the five cities I looked at, this is the highest density zone. There's no floor area ratio limit, but limits on height (550') and tower width means an FAR around 20. library.amlegal.com/nxt/gateway.dl… 14/
That said, there's not a lot of 550'+ zone in San Francisco. Just a few blocks total, and some of it is used by office buildings. library.amlegal.com/nxt/gateway.dl… 15/
New York City's highest density residential zone is R-10, which has a max floor area ratio of 12. Compared to SF, NYC towers are allowed to be wider. Image from NYC Planning website www1.nyc.gov/site/planning/… 16/
While each individual lot isn't as dense as San Francisco, New York has hundreds of blocks with high density zoning, vs. SF's handful. NYC zoning map: www1.nyc.gov/site/planning/… 17/
New York also has many buildings - such as the super-skinny towers popular with policy failures that go way past the 12.0 floor area ratio limit by buying up transferable development rights from adjacent historic buildings. www1.nyc.gov/site/planning/… 18/
Miami uses New Urbanist form-based zoning (the transect). Their highest density zone is T6-80, which allows 80 stories and a floor area ratio of 24. miami21.org/T6_Specific.asp 19/
While Miami has very high floor area ratios, as much as 1/3 of it is often used up by aboveground parking garages (car-dependent city, high water table means no basements) Example photo by Ines Hegedus-Garcia, CC BY 2.0 commons.wikimedia.org/wiki/File:The_… 20/
The entire coast of Miami is T6 zones, with height limits ranging from 24 to 80 floors. As sea levels keep rising, this may be the only area valuable enough to raise and get new infrastructure, surrounded by miles of ocean in every direction. miami21.org/zoningatlas.asp 21/
Next time, we'll look at houses in Japan, Europe, and the US, and how small lots or rowhouses can create relatively high densities. 22/
