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Interactive video lesson plan for: How To (Safely) Demolish A Building

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When demolition companies “blow up” a skyscraper, they’re actually imploding the structure. So how do they collapse a building without destroying everything around it?

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Have you seen a demolition company blow up a skyscraper… without affecting any of the other buildings around it? Obviously science (and you know… explosives) are used to control the collapse, but how exactly do you demolish a building so that it falls inward?

Well, the trick is to “implode” the building, rather than “explode” it. This way, it collapses down to its “footprint” -- the area defined by the perimeter of its structure. An implosion only takes a few seconds. But the preparation to get it right… takes years.

The people who control building demolition have a pretty cool job title: “blasters.” Before any of the explodey stuff happens, though, the blasters have crews take out non-load-bearing walls and weaken support columns. And of course, before loading the explosives, the blasters have to decide what type and how much to use. There’s all kinds of explosives used on different materials, but let’s boil it down to two of the most common: Dynamite and RDX.

Good ol’ dynamite is basically an absorbent stuffing that’s soaked in combustible chemicals so it burns really quickly, producing a large amount of rapidly expanding gas. It’s usually used on concrete columns, stuffed into bore holes that’ve been drilled. The resulting outward pressure is so immense that it creates a shock wave that shatters the concrete.

But when a building’s got steel columns, that’s when we break out the RDX, which can expand up to 27,000 feet per second. Its explosions can slice through steel, splitting beams in half.

So the blasters decide how to position their explosives of choice through the building. Now, before they push the button, blasters have to take all kinds of protective measures to ensure they won’t damage nearby structures.The blasters clear the surrounding area because (for reals) some human people actually try to sneak closer for a view.

Then the blasters sound sirens warning of the imminent detonation 3 times before they charge the lead line and push the “fire” button. Then… KABLOOMY. The building collapses inward.

Generally, blasters set it up so that when columns blow, the sides fall toward the center, crashing against each other. Usually this begins with the major support columns on the lower floors, as well as a few on the upper stories. The weight of the higher floors falling causes most of the damage — it’s gravity that really brings the building down.


Inner city blast. (2014). Demolition & Recycling International, 16(2), 18-19.

Cutting-edge techniques. (2014). International Construction, 53(4), 49-54.

Demolition a blast. (2013). Demolition & Recycling International, 15(2), 33-34.

Tagged under: brainstuff,brain stuff,howstuffworks, stuff works,science,technology,lauren vogelbaum,techstuff,fw thinking,building demolition,building implosion,demolition,tear building,dynamite,RDX,explosion,implosion, implode building, buildings torn ,skyscraper

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