An expert has described the conditions that allowed a fire to rip through a multi-storey car park in Liverpool in December, destroying 1,300 cars, as a “perfect storm”.
Alasdair Beal, principal associate civil and structural engineer at civil engineering consultancy Thomasons, said he believes changes to the way cars are designed may mean that current structural design guidelines for car parks need updating.
“It’s an accumulation of a whole string of changes in the construction of cars and car parks,” said Beal. “Each one is not a big change, but when you add them up, it has the combined effect of turning something that was practical and worked [the existing guidelines], into something that is impractical and doesn’t work.”
From photographs of the car park after the fire, Beal said he was surprised by the ferocity of the blaze and the way in which the structure had been damaged.
No one was hurt in the fire, which occurred on New Year’s Eve, but it destroyed all 1,309 cars inside and damaged the reinforced concrete structure beyond repair. At the time, the car park was full, with people attending an equestrian event at the nearby conference centre.
Beal said his first observation was that the car park was full. He said this would have maximised the potential fire load and the risk of the fire spreading.
The blaze also burned through the concrete in the central roadway, exposing the reinforcement in large areas. However, he said that in other fires, the structure under the cars would generally sustain the most damage.
A reason for this, according to Beal, could be that cars are now designed with plastic fuel tanks. These burn through more quickly than steel tanks, releasing fuel onto the structure of the car park. A natural deflection at the mid span of the structure then causes the fuel to run into the centre and pool, increasing the fire in that area and damaging the structure.
He also said an increase in the use of diesel cars would be different to the assumptions on which the design guidance for the structure was based. In a fire, he said, diesel tends to form burning pools and rivers rather than vaporising and exploding like petrol. This would also have allowed the fire to spread more easily.
Additionally, he said, cars had become wider, their components more flammable, and the fuel tank size had increased. Wider cars would narrow the allowed for gap between the parked cars, increasing the ease and rate at which fire spreads, while larger fuel tanks release more fuel into a fire.
The engineer said the Liverpool fire should act as a warning and that the guidlelines should now be reviewed. He also warned that changes made to the guidelines could take years to come into effect and it would not affect the existing car park stock.
“It’s a warning – if it could happen there once, it could happen again,” said Beal. “If the analysis is right, then it means that the risk of fire is now much greater than it was before, and that applies to both new and existing ones.
“It’s something that you also have to be looking at changing the management of the existing car parks and what can you do to those to decrease risk.”
Liverpool City Council said it was still awaiting a report on the condition of the car park from structural engineers, but investigations had been complicated by the lack of access to the unstable structure.