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Fri July 12 2024

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Engineers re-think car park design

5 Jun 23 Multi-storey car parks built in the 1970s are unlikely to be fit for the modern world, engineers have warned.

The Institution of Structural Engineers (IStructE) has re-written its codes for designing car parks, citing how cars have got heavier in recent years – from 1.5 tonnes in 1974 to almost two tonnes today.

The institution’s Design recommendations for multi-storey and underground car parks has set the standard for car park design since 1976. After more than 45 years and four editions, this new guidance provides new and updated information for anyone involved in car park design, construction, maintenance and reuse.

While many reports have focused on the weight of the batteries in electric cars, even petrol cars tend to be considerably heavier that they  were just 30 years ago. A 1991 Ford Escort V 1.6i weighed 1045kg. A regular 2023 Ford Focus weighs up to 1543 kg and a Ford Kuga up to 1844 kg, depending on specification. A battery-powered Tesla Model 3 weighs 16726 to 1847 kg.

So the changing fuel of the average car is less of an issue than the changing size and design. Cars are wider now, and so need wider bays. They are heavier –  battery powered or not – so structures and decks need to be more robust. And battery charging infrastructure is now generally a requirement.

The guidance explains that car parks need to be designed to handle changes in car design. The average vehicle’s weight has risen from 1.5t in 1974 to almost 2t today – due to electric and hybrid batteries and the size of cars increasing. This extra load and the changing fire safety requirements are all considerations not just for new car parks, but for existing structures too. 

Ten experts contributed to the guidance including overseeing consultant, Chris Whapples, who said: “There are myriad considerations the design of a modern car park needs to address, particularly as selling petrol and diesel cars and vans will be banned in the UK by 2030, and hybrid cars and vans by 2035. Car park safety is paramount, especially given the learnings from structural failures, including the Pipers Row floor collapse in Wolverhampton, UK in 1997. And this guidance is made increasingly relevant with the recent, tragic collapse of a car park in Manhattan, New York which is currently being investigated.”

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The guidance is spilt in two parts: part one is aimed at those involved in procuring a car park, including clients, architects, and project managers among others. Part two covers more in-depth design issues, with recommendations for those engineers responsible for the detailed design.

The report highlights that a number of serious fires have happened in car parks which were designed to current guidance, and that in certain circumstances, this may not produce a fire-safe design. 

Structural engineer Mark Punsdack, who was chair of the contributor group, added: “As we move to using more electric or hybrid cars, we are now exposed to risks from vehicle compositions and propulsion systems which current design guidance does not acknowledge. We have moral and legal duties to make buildings accessible for all — and car parks are no exception.” 

Other aspects of car park design considered in the new document include accessibility – there are more motorists with personal mobility issues than in the past – and physical measures that can be part of the building to deter suicide attempts.

Mark Pundsack concluded: “The car parks built today or those being renovated and re-used need to be designed with all this in mind if these structures are to remain viable and useful in a rapidly changing world.”

 Design recommendations for multi-storey and underground car parks, also known as Car Park Design, is available for £65 from the IStructE website.

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