Top Hung

Two buildings, one thing in common. They're both being demolished from the bottom up. You see The Leadenhall Building (left) and 20 Fenchurch Street (right) are both top-hung buildings. Top-hung? Sounds interesting, but what is it? Well, imagine the central core of the building as the shaft of an umbrella and the roof as the canopy (now it gets weird) from which cables hang to support the floorplates bellow and you'll have some idea. Now all this is great for producing nice big uncluttered floorspaces but not so good when you have to demolish the building. Because each cable is under such enormous tension, blowing up the building is out of the question as is demolishing it from the top down, because once the roof goes, so does everything else. So the only option is bottom up demolition.