So how are they demolishing 20 Fenchurch Street from the bottom up?

Anyone with an interest in demolition heard about the 25-storey building at 20 Fenchurch Street in London back in 2010. It's unusual because Keltbray found that the best way to demolish the building was from the bottom up. To the onlooker passing the building regularly, they got the unusual site of the building disappearing from the ground up rather than the more conventional top-down approach.

So why did Keltbray choose such an unusual method? The answer lies in the roof structure, which is huge because it was used to suspend all the floors from above. The roof took up 3 floors worth of space and used post-tensioned concrete beams more commonly seen in bridges. By doing this, the designers maximised the interior space, but also posed a problem for anyone tasked with demolishing the building.

If you'd like to know in great deal how exactly the 20 Fenchurch Street building was demolished, then head on over to the great article at Building.co.uk, which takes you through the whole process.