Electric cars are no longer welcome in the rooftop parking lot of the Carrefour supermarket in Kraainem, a municipality in the Belgian province of Flemish Brabant. The ban is in place because EVs are heavier and therefore have a greater impact on the building, according to the newspaper Het Laatste Nieuws.

According to Carrefour, there is no immediate danger; this is merely a precautionary measure.

Greater impact on the building due to the weight

The parking ban on the rooftop parking lot at Carrefour in Kraainem, near Brussels, is in place because the building dates to a time when EVs were not yet in use. “EVs are heavier than fossil-fuel-powered cars and therefore have a greater impact on the building”, says Mich Vergauwen, spokesperson for Carrefour Belgium, on the VRTNWS website. “The measure is not being implemented at every Carrefour store with a rooftop parking lot but is being evaluated on a case-by-case basis.”

Carrefour Belgium also emphasizes that there is no immediate danger, but that they want to avoid any risks. For example, if the entire rooftop parking lot were filled with EVs, the load would indeed increase, although Carrefour Belgium also points to fire safety standards.

A difference of 300 to 500 kg

EVs are significantly heavier than comparable cars with internal combustion engines. This is mainly due to the heavy battery pack.

The average weight of a gasoline-powered car is approximately 1,300 to 1,500 kg. For an EV, or a larger SUV, that figure is around 1,800 to 2,200 kg, although, for example, the BMW i7 weighs 2,615 kilos – which is still less than a Land Rover Range Rover SUV, which weighs 2,810 kg.

An average EV therefore weighs 300 to 500 kg more than a comparable car with an internal combustion engine. That amounts to the weight of about 4 to 6 additional adults per car.

Many rooftop parking lots in Belgium were designed according to the standards in effect when they were built, namely, those of the 1970s, 1980s, or 1990s. Back then, the average car weighed only about 800 to 1,000 kg.

Today, cars are not only much heavier, but they also concentrate all that weight on a much smaller area (the battery is often located centrally under the car), which results in a much higher point load on the concrete floor.

Reinforcements measures

Worldwide, there are no known cases of a parking garage collapsing solely or directly due to the weight of EVs. However, in the UK in recent years, dozens of parking garages, primarily underground ones, have been temporarily closed or have required costly reinforcements because their floors no longer met the standards for heavy modern cars.

In the Netherlands, several municipalities and property management companies, such as Q-Park, have announced that they will need to renovate old parking garages or impose weight restrictions.

Fire safety remains the primary concern

But fire safety is at least as important for a parking lot or garage with EVs as building codes.

A battery fire, or thermal runaway, in an EV is extremely difficult to extinguish. The fire can reach temperatures of up to 1,000°C to 1,200°C and lasts much longer than a fire in a gasoline-powered car. Furthermore, the vehicle fire can reignite after being extinguished.

Extinguishing an EV also requires an enormous amount of water – sometimes tens of thousands of liters. That water, mixed with toxic chemicals from the battery, must be safely drained away. On a rooftop parking lot, the drainage system is often not designed to handle these volumes, which poses risks to the structure and to the supermarket below. Plus, the toxic smoke can enter the store below through stairwells and elevator shafts.

Insurance companies also do not currently consider the weight of EVs to be a major risk to buildings or parking lots; fire safety remains the primary concern.

According to the current Eurocode for parking garages and parking rooftops for passenger cars and light delivery vans (Category F), structures may be designed to accommodate vehicles weighing up to approximately 30 kN, which corresponds to approximately 3,1 metric tons.