Paris’ grey skyline could turn green if roof garden idea approved

An award-winning concept by three French students is under review by technical experts and could offer the city solutions for cooling and biodiversity

Paris rooftops
Many Paris buildings have over-designed load-bearing walls perfect to support rooftop gardens
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Paris’s signature grey zinc skyline could soon be getting a green make-over after authorities gave the go-ahead to a prototype rooftop garden.

It is the brainchild of three postgraduate French students who teamed up while studying at the prestigious Massachusetts Institute of Technology (MIT).

Company makes roofs climate-friendly

They formed a company, Roofscapes, to put their ideas into action and immediately won an MIT prize for being one of the most promising new firms of the year.

Olivier Renaud Faber, one of the trio, said: “Our interest was in ecological solutions and rooftop gardens, which have been experimented with for years and are efficient at cooling cities and improving biodiversity.

Read more: June heatwave in France prompts huge ‘cool cities’ budget, but no plan

“We feel there is a lot of potential in maximising the buildings we already have, and making them more climate-friendly.”

Load-bearing walls can hold gardens

Their breakthrough came when they realised many European cities, including Paris, were dominated by 19th and early 20th century buildings with over-engineered load-bearing walls, strong enough to take the weight of garden platforms.

“A city like Paris, with its pitched, zinc-soldered roofs, does not immediately lend itself to rooftop gardens – the roofs often have a steep pitch and are irregular,” said Mr Renaud Faber.

“But once you look behind the roofs, you see load-bearing walls built out of dressed stone which, until after World War Two, were very over-designed for the weight they carry.

“They give you spans of between six to eight metres, which can serve as the base for platforms over the roofs.

“If these are set back, the gardens are not seen from the street, but still play a large part in regulating temperatures, as well as offering somewhere a bit green for residents and the possibility of growing food.”

Paris has the right roof expertise

He said they were initially worried that the complexities of installing the gardens would make their solution unworkable.

“However, when we started looking at how Paris’s roofs are maintained, we realised there is tremendous know-how among people who work on the roofs, and they were not put off by our designs at all.

“They know how to make waterproof traps and openings for supports, and could build them tomorrow if the regulations allowed it.”

Roof access already exists

Unknown to most residents, almost every building in Paris has access to the roof space, often through a trapdoor in the ceiling of the top-floor service staircase.

These could be transformed into the main access to the roof gardens.

“But it is a political decision to allow these rooftop gardens, including the basic question of who will have access to them,” said Mr Renaud Faber.

“Should all owners of properties in the building have access, or only those with flats on the top floors?

“And should access be allowed to other people in the neighbourhood, including those with low incomes, or should it be reserved for the people whose building syndicates pay for it?

“Lockdown showed that many Paris flats are too uncomfortable to live in if you cannot get outside.”

Prototype planned for 2023

Roofscapes’ technical guidelines are currently being evaluated by experts with the aim of building a prototype in Paris by the end of 2023.

“Once proved, we hope to get lots more work, in Paris and elsewhere. Local carpenters will do the work,” said Mr Renaud Faber.

The platforms will be built out of wood, probably pine or oak, and will be able to support small trees in large pots, shrubs, and raised beds for flowers or vegetables.

“Depending on the roof, the gardens might be flat, or set out in a series of steps.

Roofscapes is also considering gardens on top of warehouses, of which there are many in the Paris suburbs, that could be used as market gardens.

“Hopefully, we will be able to convince those in power and soon see these ideas in place.” said Mr Renaud Faber.

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