Comment by milesvp | Hacker News Reader

Comment by milesvp | Hacker News Reader

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Any building taller than 15 stories is likely already sacrificing square footage for height. As I understand it the square footage maximizing height with modern building techniques and materials is somewhere around 15 floors. As you go taller you need to start sacrificing internal volume for more reinforcing material and, surprisingly (to me when I learned this) elevators. The taller you go the more elevators you need to quickly move people around.

I’m curious if this just isn’t already well known in the zoning world? We build tall buildings because the higher floors are more valuable which make up for the smaller amount of total real estate. Logical extension of this is to sacrifice whole floors for height if that is what zoning required. I’m also curious how long it took someone to figure out this loophole (since it’s easy to say it’s obvious after the fact).

It's not "sacrificing" square footage for height, it's just encountering diminishing returns. To say it's sacrificing for height, means square footage decreases with increased height.

What actually happens is square footage per floor decreases with increased height. But a 20 or 80 story building still has strictly much more square footage than a 15 story one, perhaps excepting the absolute narrowest buildings.

Profit per floor can decrease as well, due to increased costs of the structure.

Sure, but total profit still goes up.

And due to the premium you can charge for the upper floors, there's eventually an inflection point where profit per floor starts increasing again.

As far as I can tell, rentable square feet (total) per building footprint sqft goes up with height, just sub-linearly. Until adding more height is technically infeasible or decreases total projected profits (whether that's due to decreased profits/sqft, or not enough demand to fill a taller building, or both), developers in land-constrained areas like city centers will build taller buildings.

(Land-constrained, as in, when buying two equivalent lots and building half-height buildings becomes less profitable than building a skyscraper or supertall, due to massive demand for high-floor views, combined with sky-high nearby lot prices.)

Point of trivia: apparently there are terms for each 100m of height: Lowrise -> Highrise -> Skyrise (Skyscrapers) -> Supertalls.

Who here played Sim Tower

I head from an architect that in most of Manhattan that the level where structural difficulty gets harder is just above 20, maybe 22 stories. That slightly higher level may be due to lots of Mahattan having solid bedrock close to base upon.

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