Mike Kehoe, managing director of demolition specialists C&D Consultancy, has been bringing down old buildings for decades. He talks explosives, cats that emerged from the rubble, and the minute before the button is pressed...
Did you have a destructive streak as a kid?
I suppose I must have done, because my father and grandfather were demolition men, and from the age of one or two, my earliest memories are being on demolition sites. It must be in my genes somewhere and because I had a liking for it, I knew I would get into it.
What was the first thing you ever blew up?
My first job was cutting down massive oil tanks when I left school at 16; the explosives only came into it much later. I’ve been involved in that for about the last 10 years, but prior to that it was often city centre demolition and the use of explosives wasn’t common.
Is it all as exciting as people imagine?
I think as I get older, I probably get even more excited because I understand how a building reacts now. I enjoy the challenge of either demolishing a building or blowing it up because of the expertise I now have — I recently did a job in the UK where we were bringing down a car park that had a police HQ with a live computer system just 50m away. There are lots of challenges, and that minute before the button is pressed is probably the most nerve-racking 60 seconds that you’ll ever have.
What are the best tools at your disposal when it comes to bringing down a building?
The demolition industry is probably one of the most forward-thinking around. People still imagine us using an old ball and chain, but now we have super-high reaches that can go up to 90m costing as much as Dh19m. There’s a lot of robotic kit in the industry as well: remote-control robots that assist with the demolition process so it’s not putting people in danger. We’ve even got exoskeleton suits that are starting to come in where operatives can wear hydraulic suits so that they don’t get any muscular injuries.
What about explosives? What’s in the arsenal?
There are different explosives for different jobs — for cutting through steel we’ll use shaped chargers that will cut through steel like a knife through butter. We’ve got traditional dynamite, which is used to blow concrete apart, and we’ve got different types of detonating cord that can be joined together, popped inside a concrete column and the heat and energy will blow it up.
Is it terrifying to handle?
No, where explosives become dangerous is when they are detonated, and we need to make sure that doesn’t happen accidentally. So we keep the site sterile and free from any kind of electrical current so as not to set it off.
Do you use computer modelling to work out how best to bring down a building?
Yes, we can model where the building is going to fall and we can compute the dust pattern. We can also measure the ‘air-over’ pressure; if you can imagine you’ve got a 26-storey tower block and you’re going to compress it, all of the air on each of the floors has got to go somewhere. We can then work out ways to stop that from breaking windows and so on by using containers, straw bales or water breaks.
How far can rogue debris fly?
There was an incident about 25 years ago – not one we were involved in – where a piece of debris exited a site and there was a fatality; what we do as a company is to make the exclusion zone a lot larger. It’s a bit more difficult to control, but we like to think it’s safe.
The old adage was one-and-a-half times the height of the building for a safe exclusion zone, but we tend to do two- to three-times the height. Plus, we’ll wrap chain link fencing around the columns that are being exploded and we use a certain type of cloth material to prevent fragmentation leaving the site.
What was the most difficult job?
One of the most challenging ones was in Liverpool where two tower blocks had been blown by a contractor and they didn’t come down. They’d also tried to pull the buildings over mechanically and that hadn’t worked.
So when we arrived, it was a very precarious site: the buildings had been pre-weakened, there was still the possibility of live explosives inside, it was only about 10ft from the closest house. Within three days we’d brought in the biggest high-reach in Europe and we got the tower blocks down within two days.
Have you ever sat and watched the dust settle only to see a cat emerging triumphantly from the rubble?
Yes, a few times. I’ve seen lots of animals emerge from the dust, mainly rats, but there’s been the odd cat — thankfully not a black one.
Do most people in your field have a big grin on their face when they press the button — or are they worried about things going wrong?
We plan for things to go wrong. We think about what happens if the explosives don’t go off, for example: have we got an alternative plan? Pressing a button takes a second, but there’s often 12 months of planning beforehand and we try and think of everything.