By studying historical construction data, the researchers were also able to determine that at the extreme, the most a deep bedrock could add to the costs of a building is about 7 percent, and therefore negligible when it comes to the economics of construction. Barr said.
Probability of skyscraper locations. Growing up on Long Island in the s, Mr. Barr said he used to be scared of the big city, but after he started hanging out here on weekends, coming down from Cornell to visit a friend at Columbia, he fell in love.
Still, he stumbled onto his specialty the way most of his colleagues do. Like cavemen following mammoth across the Bering Strait, early developers were following their prey. That land was cheap, but the location was worthless. We get it: you like to have control of your own internet experience. But advertising revenue helps support our journalism. But to get it, the developer must first pay for the land and the cost of construction.
Thus, the location and height of a skyscraper are determined, fundamentally, by the income relative to the cost of producing it, or, in real estate parlance, the return on investment. Lower Manhattan was, arguably, the densest business district in the world. This clustering was bidding up land values, which was signalling to landowners that the demand for those locations was rising fast.
But, of course, they had to contend with the geology. The myth states that since the bedrock is just below the surface in lower Manhattan, skyscrapers were simply thrust down upon it like an empty beer can on a table. But this is not true. In fact, Downtown, from Wall Street to City Hall, has some of the worst geological conditions on the island.
Builders in lower Manhattan built skyscrapers not because of the geological conditions, but despite them! Just below the ground level, atop the bedrock, sit uneven layers of sand, gravel, and clay, with large boulders scattered throughout. Beneath the waterline, the sand morphs into a wet, viscous goo, known as quicksand. This was a major problem for developers in lower Manhattan.
The solution was the caisson—a large cube with no bottom. The box would slowly sink. Once it hit the quicksand, compressed air was pumped in to keep the soil out.
Eventually the box would reach the bedrock. It was then filled with cement, and piers were built atop it up to the basement level to hold up the structure. But make no mistake: using caissons was expensive and dangerous.
Builders sometimes ask why foundation work costs so much in New York. No matter how carefully the site may have been bored, boulders or quicksand are liable to appear….
All perilous work is expensive, because men of robust physique and of sufficient bravery hourly to risk death are hard to find. How do we know? Because, using geological maps, we can ascertain the bedrock depths below the earliest skyscrapers. And what do we see? The figure below shows the depth to bedrock below a sample of buildings in Manhattan as of the vertical axis versus its location relative to the southern tip of the island.
The hump shows that as we go from south to north the bedrock depths increase into a valley. Then, continuing north, the rock moves closer to the surface. We can also see that a few skyscrapers, most notably the Woolworth Building , 55 stories and the Municipal Building , 40 stories —the highest triangles in the figure just above the City Hall indicator—were constructed over some of the worst geological conditions.
But, just as importantly, on the north side of the valley between Canal and 14 th Streets , there are no skyscrapers where the bedrock is relatively accessible. If bedrock depths were key, we would likely see them where it was easy to build. Rather, we see none. The reason was the lack of demand for such projects discussed below. The bedrock myth ignores the cost of construction in lower Manhattan.
But the terrible conditions below the surface made them high, in both blood and treasure. Then, why did builders persist? The heights of buildings in New York City over the last years consistently demonstrate a strong relationship to the underlying economic climate—as rents and real estate prices go up, so do building heights on average, when rents and prices go down, so do building heights.
But when one actually does a series of statistical, objective tests, one can show the curse is not true. Cookie banner We use cookies and other tracking technologies to improve your browsing experience on our site, show personalized content and targeted ads, analyze site traffic, and understand where our audiences come from.
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