When people bought multi-million dollar condos in San Francisco’s Millennium Tower, they probably thought they’d bought into a foolproof investment. After all, the San Francisco housing market has skyrocketed since the beginning of the tech boom; a million dollar condo in San Francisco, bought ten years ago, is now worth several times that. So they’re understandably furious that, just a few years later, their homes are now worth nothing.
That’s because Millennium Tower is sinking. Well, half of it is. Since the 58-story building was completed in 2009, half of it has sunk 16 inches, giving it a pronounced northwestern tilt. Occupants of the luxury tower have demonstrated the tilt for reporters by rolling a golf ball across the floor and watching it curve dramatically to one side. Why does Millennium Tower tilt? There are multiple reasons, and like most home improvement disasters, they’re mostly related to cost-cutting. First, the tower is built of concrete instead of steel – concrete is much cheaper, but it’s also much heavier. The tower is also built on a landfill, and as you might imagine, thousands of trash bags full of disposable diapers and banana peels isn’t the most stable foundation for a 58-story apartment building. But what about the foundation? Well, the builders skimped out on that too, setting down an experimental foundation that was much smaller – and much cheaper – than a conventional one. It hasn’t worked out. Now the tower, which cost $350 million to build, is looking at a repair job that could cost over $500 million.
But as dangerous as they may seem, tilting buildings aren’t inherently dangerous. Just because a building tilts doesn’t mean it’s inevitably going to fall. Take, for example, the world’s most popular site for taking unfunny photos; the Leaning Tower of Pisa. It was built over 800 years ago and is still standing tall-ish. Construction on the tower began way back in 1173, and by the time they started work on the second floor, only three years in, the tilting had already begun. So did they halt construction and correct the problem? Nope. They went to war with a neighboring republic for a hundred years. When they came back to the tower after a century had passed, the soil had settled enough to stabilize the tower. They finished it, and it lasted just fine until the 1990s, when officials reinforced it with cables and straightened the tower by a few centimeters by digging out from under the higher side of the tower.
In Windsor, England, is a house even more tilted than the Leaning Tower or the Millennium Tower. Built in 1592, the Crooked House of Windsor was torn down by the city in 1687 to make way for a new building. But when the owner protested, the city council reversed its decision and ordered that the house be rebuilt. The city must have hired the cheapest builders they could find, because the replacement house was built with unseasoned green wood. As the wood dried, the structure of the house buckled and warped. Today, the vertigo-inducing house is a cafe, and a minor tourist attraction. And unlike most of the other buildings on this list, it didn’t require any reinforcement.
Most leaning buildings do, though. The Pisa tower was repaired with cables, a redug foundation, and lead counterweights on the high side of the building. But what about Millennium Tower? Experts are considering several options, ranging from building a concrete “collar” around the building, to inserting “micropiles” – basically long concrete rods – under the shaky foundations, to anchor the building to the bedrock below. Both of those solutions would cost hundreds of millions, and take years. But the simplest and best solution might be the one that sounds the most ludicrous; build a new building directly next door, and let the tower lean on it like a drunk at closing time. As stupid as it sounds, it’s already been done. In 1907, the Fisher Building in Chicago began to tilt precipitously. The owners bought the lot next door and built an even bigger, taller building that rubbed shoulders with the original building. Once the tilter settled into place, the two buildings together were as stable as any normal building, and are still standing tall today. I just wish I could be a fly on the wall when the San Francisco developers ask the bank for a few hundred million more dollars to build a second luxury skyscraper on top of the marshy landfill, to prop up the first luxury skyscraper on top of the marshy landfill.