Rooftop essay

Last year we first released a rooftop essay, Playgrounds for the Imagination, written by Sereh Mandias. A second eassay has been written for this years’ programme: ‘Halfway between the gutter and the stars’. Author Teun van den Ende, head of urban development at Vers Beton, reflects on both the rooftops and the city in and after this time.

Read the text below. Or have a look at the pdf here.

Halfway between the gutter and the stars

Towards an inclusive roofscape

Text: Teun van den Ende

Never in his wildest dreams could the inventor of the flat roof have predicted the effect of his discovery on Western architecture. Rotterdam is blessed with an expanse of flat roofs equal in size to 3,700 football pitches — but how should the city deal with them in the future?

Startled by the corona pandemic, we view the future in a new light. This essay outlines a future in which the imagination is seized upon to achieve a balanced and more inclusive city, by building on the shoulders of giants. 

Why do we build? The most basic answer to that question is: ‘to put a roof over our heads’. Yet the roof occupies a modest place in architectural history, though there are exceptions. Le Corbusier (1) designed a roof to resemble the deck of a steamship, where children were free to play. Or take the viewing towers in American and Asian metropolises, as exemplified by the sky deck. Roofs fire the imagination and offer fascinating views of our everyday environment.

For centuries Western architecture envisage the roof as a place for people. The introduction of the flat roof in 1787 heralded a change. For that was the year the Swedish admiral Arvid Faxe obtained a patent for a bituminous roof: “paper impregnated with copper and iron sulphate, nailed to timber planking and then painted with hot wood-tar and sprinkled with sand”. In other words, a roof based on paper.

This innovation reached the Netherlands in 1839 with the appearance of an extensive essay in the Nederlandsch Bouwkunstig Magazijn (2) entitled ‘Roofs covered with paper’. But it was not until the second half of the 19th century that the material we now call bitumen — and hence the use of the flat roof — became common in the Netherlands (3). Architects initially resisted it, viewing it as a form of architectonic superficiality. Yet advocates also voiced their support with articles such as ‘The right to use the flat and gently inclined roof in the Netherlands’ (4).

Rotterdam architects only embraced the flat roof on a large scale after World War II. Its use dovetailed with the ideas of urban planner Cornelis van Traa and a handful of prominent industrialists, who planned the new city centre on the basis of economic motives. Buildings for banks and insurance companies and emergency shops appeared first, followed by industrial buildings, cultural buildings, hotels, shops and apartment blocks. The vast scale of the post-war reconstruction effort produced a huge expanse of flat roofs. Yet while the flat roof had definitively become part of Dutch architecture, architects failed to seize on the potential of using the roof as a place for people.

View of new buildings on the Blaak when the Reconstruction of Rotterdam takes shape in the 1950s.

The roof as the start of something new

Today the city of the post-war reconstruction period is embraced as the very basis of Rotterdam’s identity. In fact, whole areas of the city centre are designated as cultural heritage. But the pragmatic and functional architecture of the generation of Maaskant, Van Tijen and Kraaijvanger is also an invitation to ‘continue construction’ on the city, taking the roofs as building plots. How, then, should we value the existing architecture?

The Municipal Committee for Buildings and Monuments takes a strong position on the subject (5), which covers more than just the layer added during the post-war period: “The Rotterdam Layer refers to a coherent ensemble of built fabric characterized by similar height, materials and façade rhythms. (…) If structures are added on top of existing buildings, it is important that such additions can be distinguished from the existing architecture so that the original height and architectural character remains visible. In the case of new development, the Committee always argues for an interpretation of the Rotterdam Layer as a recognizable layer in new volumes.”

Until quite recently, it was very common to erase traces of the past in Rotterdam. The Commission, by contrast, now stresses the cultural significance of built heritage. History should be passed on to future generations through architecture. Adding structures on top of existing buildings on a large scale might seem like uncharted territory, but architectural history reveals plenty of examples of the continued construction of the city layer by layer. 

Take the Forum Romanum, site of the market in Rome seven centuries before Christ. In the centuries that followed, flooding from the River Tiber carried sediment from the surrounding hills and deposited it on the Forum and between the buildings. Romans then used this mixture of earth and building fragments as the foundation for new temples and market halls, and this process continued for centuries. Excavations in this underground encyclopaedia up to 25 metres deep now allow us to analyse the remains of Roman architecture.

By way of analogy, the ‘Rotterdam Layer’ could also manifest itself as a layer of urban fabric, albeit above ground. The area of flat roofs, some 3,700 football pitches in size, can be read as a series of sites for development and transformation — as a canvas of Maaskant and Kraaijvanger ‘pedestals’ onto which new generations of city dwellers and architects can project their ideas.

Map of the Roman Forum with in black the map of the Roman Empire and in red the 19th century city map. From: Murray, J., A handbook of Rome and the Campagna, 1899.

The Post-Corona City

Although the city usually manifests itself as a solid, static entity, it is also subject to social shifts and mutations. Major turnarounds in our attitudes towards shaping the city are usually prompted by crises. At present we are witnessing severe social unrest because of the corona pandemic. The crisis is a sign that, having indulged in endless liberties for years, we have hit a rock-hard wall.

Those borders have been crossed in many European city centres with the allocation of space primarily for the entertainment of visitors. Now that the cogs of the tourism industry have ground to a halt, businesses and city marketing departments have seen their income drop considerably, but many of the city’s residents are no doubt breathing a sigh of relief, for suddenly there is space in the city again for the daily activities.

The lockdown has also destroyed the revenue models of companies that exploit urban space and thus undermined urban resilience. Whether it be guest rooms (Airbnb) passenger seats in cars (Uber) or hotel rooms (, online services have turned out to be of little value without a functioning tourism industry. Market values plummeted and even had the audacity to appeal for government support. Yet the question is whether the exploitation of urban space will simply start all over again after corona. For lurking in every nook and cranny of the city is a new business opportunity.

This applies fully to roofs. From infinity pool to rooftop bar, the roof is usually a place of pleasure for the international urban elite, a place where fortunes can be earned. For the rich are only too happy to take refuge in their penthouses, elevated far above the rabble. The upper layer of the city exudes exclusivity. Who says that a smart company will not capitalize on that vast upper layer as the exclusive domain of the tourist? Bingo.

But there are alternatives. Similar to the landscape around the city, the upper layer has the potential to be a public space for the enjoyment and benefit of both visitors and inhabitants. Such an accessible layer for the whole community is the opposite of exclusive — the roofscape as inclusive city, as an antidote to inequality, as a meeting place and resting point halfway between the gutter and the stars (6).

Towards an inclusive and multifunctional roofscape

Ever since the roof became a place for people, it has fired the imagination of city dwellers. Rotterdam is one of the few Dutch cities that can boast a number of publicly accessible roofs. Access to the roof of the Hofbogen structure, for example, has been created (for everybody except disabled people, a point of attention among designers) by making entrances to it on both sides. The public garden is open all year round, making it an inclusive space. In the summer period it becomes a space for culture as a setting for dance performances and film screenings. 

A little further on, the Schieblock is topped off with a public Rooftop Farm, featuring a vegetable garden and terrace. A rooftop café invites you to stay, but if that doesn’t appeal, you can take a short walk past several beehives and the Smart Roof that serves as an experimental site for buffering rainwater. This technique had been dubbed a ‘polder roof’ and will soon be applied on a much larger scale on De Doelen concert hall.

Roofs are thus starting to acquire the functions of landscapes. Cooling the city on hot summer days is vital, especially since the climate, with summer temperatures almost 10 degrees higher than the surrounding landscape, is becoming unliveable. But can we be so certain that the Rotterdam roofscape, like the ‘real’ polder, will remain publicly accessible in the future?

“The Rooftop Farm and Smart Roof will be maintained, adding a unique semi-public space to the city.” That’s a statement from design office ZUS and developer Lingotto in their redevelopment plan for the Schieblock (7). And the Dudok group, owner of the Hofbogen, sees the future of the two-kilometre-long national heritage site as part of an ‘inclusive cultural city’ (8). But given the trend of big companies exploiting urban space, that access is not self-evident in the long term. 

Public roof of the Hofbogen, Rotterdam, 2018. © Ossip van Duivenbode

The value of parks and canals

Landscape has long been part of the city in the form of public parks and canals flanked by greenery. One of the advocates of that was landscape architect Frederick Law Olmsted (1822-1903), who created a shared urban space with his design for Central Park in Manhattan. He viewed his park design as “an oasis, an arcadia in the desert of brick and mortar vibrant with happy life for morning to night”. Olmsted understood that the park had to offer space for urban life in all its diversity. The park, which covers no less than 5.7% of the surface area of Manhattan, deprived property investors of development land, but it also raised the value of all property built near the park.

You could call the Water Project the Rotterdam equivalent to Central Park. It consists of a network of canals flanked by greenery: Westersingel and Mauritssingel, Spoorsingel, Noordsingel and Noordplein, Crooswijksesingel and Boezemsingel. It was the brainchild of city architect W.N. Rose (1801-1877) and designed by the landscape architects L.P. Zocher and J.D. Zocher. The Water Project came about out of necessity. Up until then, Rotterdam had had a very inadequate system of water management. The water system collected rainwater and waste water, acted as a dump for waste, and provided a source of potable water, all at the same time. This frequently caused outbreaks of cholera. The disease was only overcome after the founding of the Rotterdam Potable Water Company in 1870 and the construction of the municipal sewers from 1883 on.

The effect of the Water Project on public space in Rotterdam can scarcely be underestimated. The robust network still serves as a buffer for heavy rainfall, provides cooling in the summer, and acts as an ecological habitat for flora and fauna in the city. Moreover, properties overlooking the canals have maintained their value, just like those around Central Park. The homes are still as popular as ever, and in 2011 they were designated as a protected streetscape.

Despite this success, in its quest for economic growth, in the 20th century Rotterdam filled up many of its canals, among them Coolsingel, ’s Gravendijkwal and Schiekade to let traffic ‘flow’. Road marking, traffic signs and traffic lights protect pedestrians and cyclists from the cars racing past, but they also distract and obstruct views of the surrounding city and its architecture. Today the facades that line these former canals are covered in soot.

Design W.N. Rose for the Water Project, 1858. From: Scan of Cultural heritage in 19th-century neighbourhoods in Rotterdam-North, August 2013

The wonder world of roofs

The current crisis is opening the eyes of many city authorities, who are greening public spaces in their cities and allocating more space for pedestrians and cyclists. In Europe, Milan was the first city to implement far-reaching measures with a plan to replace 35 kilometres of streets with cycle paths and sidewalks (9), and many other cities have followed suit. If cities really continue along this path after the current crisis, it will help to make them more inclusive places. For the city designed for the car is a danger to children, seniors and the disabled (10).

Rotterdam, like Milan, still has a long way to go in reducing the car’s dominance. In the meantime the roofscape, free of traffic, can serve as a testing ground for inclusive forms of using space. However, designers must be afforded an opportunity to enliven this urban layer with images of possible futures.

Designers possess the necessary imagination, but how we can unlock it? The cultural institution Schunck, housed in the Glass Palace in Heerlen, set up the Heerlen Rooftop Project for that very reason. It launched a competition to redesign seven roofs, among them the Glass Palace itself. The goal: to transform the often ugly grey expanses of roof into an attractive and accessible roofscape.

Of the three competition winners, the project submitted by the young design collective Selvatico (Giulia Azaria, Iñigo Ruiz and Linda Tonin) stands out on account of its expressiveness and imagination. Called Wonder World (11), the proposal comprises an archipelago of seven roof islands that represent a mountain range, savanna, deep ocean, desert, forest, agricultural landscape and city. The makers see these ecosystems as interventions that express the vulnerability of the earth at a time of rapid climate change, and thus as a way of raising awareness. Wonder World contributes to the stability and durability of the system as a whole. In the event of unforeseen circumstances occurring, tiny houses and work spaces are constructed in a flexible and lightweight way. 

Selvatico belongs to a younger generation of designers who are aware that the thoughtless pursuit of economic growth is detrimental to the planet, nature and animals. In its analogy with the landscape, the proposal also displays similarities with Rotterdam experiments such as the Roof-Top Farm and the Polder Roof. At the same time, it offers a feasible design for a public roof festival and is thus a 21st-century interpretation of the 19th-century park and canal designs by Olmsted, W.N. Rose and the Zochers. What all these schemes have in common is that they unite metropolitan property ambitions, public access and durable ecological balance. 

Selvatico (Azaria,G., Ruiz,I. en Tonin,L.): World of Wonder, part of the exhibition ‘Uit je dak – the Heerlen Rooftop Project’ SCHUNCK, Heerlen, 2020

Standing on the shoulders of giants

The Heerlen initiative to reimagine its roofs should be replicated in Rotterdam. The design competition not only appeals to the imagination but also challenges designers to engage with existing architecture. The appropriate attitude to do so has been explored by Jantje Engels and Marius Grootveld in the publication Building upon building (12), which documents design research into architectural dialogue. This involved asking dozens of architects to respond to an existing piece of city by means of a (fictive) design.

In their introduction, the compilers outline what in their view should characterize that attitude: 

By working within the local narrative of the city, we build upon the framework on which the story of the city has been enriched and augmented over time. The contemporary city is (…) a network of references between buildings, charged with the insights and visions of previous architects. We believe that as architects, we are not only indebted to our predecessors, for their technical invention. But rather in both composition and their style we must maintain a constructive dialogue with former generations. Hereby building upon the theoretical narrative of the city.

Building upon the Rotterdam roofscape calls for a design attitude that engages in dialogue with the city’s residential, commercial, cultural and industrial buildings. They deserve a second, and hopefully a third and fourth, life. This calls for sensitivity in dissecting the form, composition and materials of the existing city, in both the technical and cultural sense. The imagination shown by architects in that process can counter the seemingly uncontrollable inequality that exists in the city and strengthen the resilience and durability of the city. 

Investments should primarily offer the people of the city freedom and opportunities for personal fulfilment. Maybe that means that the city can no longer continue to offer unbridled freedom to visitors, but the lost revenue from tourism is more than compensated for. For Rotterdam will acquire a stacked and publicly accessible roofscape in which architectural layers far more exciting than the Forum Romanum will display themselves above ground. Everybody who views the result from above will realize that the city is built on the shoulders of giants.

The exhibition Uit je Dak – The Heerlen Rooftop Project can be visited from June 16 until August 30 in Schunck Glaspaleis.



  1. In the essay “Playgrounds for the imagination, an essay on rooftops” on the occasion of the Rotterdam Roof festival 2019, the author Sereh Mandias discusses the role of the rooftop in the work of Le Corbusier.
  2. Engel, ‘Daken met papier bekleed’, Nederlandsch bouwkunstig magazijn, 1 (1839), 277-299. The author, the Imperial Russian Architect Carl Ludvig Engel stationed in Helsinki, immediately makes clear to the reader that, despite the curious title, the article is serious: “The paper here is not the roof covering exposed to the elements but, as this essay will explain, serves only to hold together and connect the stony and inflammable outer covering. Please do not leave this article unread because of its title.”
  3. A comprehensive discussion of the development of the flat roof in Dutch architectural history has been described in: Stenvert, R.: Dak met plat van papier: het ontstaan van het platte dak, in: Jaarboek Monumentenzorg 1996. Monumenten en bouwhistorie, 1996
  4. Jan Gratema, Alb. Otten & S. de Clercq: ‘Het goed recht van de toepassing van het platte en flauwhellende dak in Nederland’, Bouwkundig Weekblad, 1917
  5. Edens, C., Michel, H. and Pronk, B. (red.), Commissie Welstand en Monumenten Rotterdam, jaarverslag 2018, Rotterdam, 2019
  6. ‘Halfway between the gutter and the stars’ is the title of an album produced by Fatboy Slim,  and released in November 2000 by Skint Records
  7. ZUS/Lingotto: ‘De toekomst van het Schieblock’ was presented to the Rotterdam city council in the context of the redevelopment of the Schiekadeblok, May 2020
  8. Dudok Groep: Toekomstvisie Hofbogen, 2019
  9. The Guardian: “Milan seeks to prevent post crisis return of traffic pollution”, 21 April 2020
  10. Verkade, T. and Te Brömmelstroet, M.: Het recht van de Snelste, De Correspondent, May 2020
  11. Wonder World can be seen in Schunck from 16 June 2020 as part of the exhibition ‘Uit je Dak – The Heerlen Rooftop project’
  12. Engels, J. and Grootveld, M.: Building upon building, NAi010 Publishers, March 2016