100 ways to make better use of urban rooftops

Patients can visit a small hospital on the roof of a hospital in Rotterdam orchard full of fruit trees. A neighboring art museum has a forest on the roof planted with birch trees that were bred to survive at a slightly higher elevation. Nearby is a nearly 4,000 foot tall building topped with a park with vegetable gardens, picnickers and grazing sheep. Pilot projects on other roofs in the city are testing the potential of small houses.

The city is a pioneer in finding new uses for an area of ​​urban space that is often ignored. In a new book called Catalog on the roof, Rotterdam architectural firm MVRDV and the organization behind an annual “roof day” festival explore more possible ways to transform roofs in the city and how the entire roof landscape could change.

[Photo: Courtesy MVRDV]

“Using the roof could make a huge contribution to the densification of the city – and it could also stop us from building more on the outskirts of our cities,” said Winy Maas, co-founder of MVRDV, in an interview published in the book is included. In Rotterdam, the team calculated that if 10% of the city’s roofs were used for housing, 15,000 small, comfortable houses could be created. Like backyard homes, tiny rooftop homes can help add new living space to neighborhoods that have already been built. Roofs can also be used to expand the space of existing apartments or to add new coworking spaces to apartment buildings.

Adding green space to roofs can help counteract the urban heat island effect: the fact that cities are hotter than rural areas due to the heat radiated from streets, parking lots and buildings. Rooftop gardens can also support biodiversity, help reduce air pollution and absorb rainwater during storms. The book looks at a range of designs, such as a ‘quiet garden’ that gives residents an oasis from urban noise; an urban farm; and a ‘green monument’ (an abandoned building that may be overtaken by nature, including on the roof).

[Photo: Courtesy MVRDV]

Other concepts range from the simple — like a rooftop space for outdoor yoga or a dog park or communal workshop spaces for DIY projects — to the absurd, like a roller coaster that starts on a rooftop and then wraps around a skyscraper. The designers also propose using rooftops for parking bicycles, as shortcuts for pedestrians or as potential delivery stations for drones.

Roofs can of course also be covered with solar panels. But the book argues for a diversity of applications. (In some cases, several applications can take place on the same roof; for example, green space can help keep solar panels cooler and run more efficiently.) And even if less than half of Rotterdam’s roofs were used for solar energy, the authors calculate, that would be enough to power a million households.

There are challenges, including the fact that most buildings have to be retrofitted to handle the excess weight on the roof. But cities should think about how to encourage new uses, the designers say. “I think we need a new Building Code, or rather a Roof Code,” Maas says in the book. “You should be able to stack the four elements – water, greenery, energy and population – like a sandwich.”

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