Rotterdam’s almost untapped roofscape offers an exceptional chance to solve large urban, and environmental problems cities are facing nowadays. Take for instance, climate change, energy transition, loss of biodiversity, and the shortage of public places. Therefore we should rethink flat roofs, and expose their potential. In many different ways, they could contribute to the development of a sustainable and resilient city in the future. Especially, multifunctional, green roofs are able to reduce heat stress, store (temporarily) water, purify the air, enrich biodiversity, and accommodate social functions, especially when there is a possibility to connect all those ‘hidden’, unused spaces in the city. There are already a lot of initiatives in Rotterdam, that come up with all different ideas to fill in the 18 square kilometers of flat roofs we have at our disposal. However, this is mostly about the (re)development of a single plot, a building block, or a street. If we really want to tackle those large urban challenges, we should not only see the potential of a single roof but zoom out and see how at a city scale the roofs could be transformed into a liveable roofscape.

This thesis explores the potential and redevelopment of flat roofs in the city center of Rotterdam and aims for a whole new flat rooftop network above the existing city. The main research question is: How can the (re)development of Rotterdam’s flat roofs be guided to achieve significant progress towards a sustainable and resilient Rotterdam? By analysing the existing urban fabric, investigating possible functions flat roofs could accommodate in relation to large urban scale problems, and seeing the technical implications and possible limitations, a proposal for a rooftop toolkit and strategy for the city of Rotterdam is formulated. The main research method is research by design. This all to support the growth of Rotterdam in the upcoming years and make the city even more sustainable, resilient and liveable in the future.

Human driven pollution is causing irreversible damage to the habitability of our planet. Due to these environmental concerns, it has become imperative to move away from petrochemical dependency as this industry contributes significant greenhouse gases causing air, soil and water pollution. About 85% of the petrochemical industry that travels through the port of Rotterdam goes towards fuels for mobility, this is a critical bottleneck that requires careful consideration. To ensure a sustainable province in terms of both a liveable province as well as economic prosperity policy is set up by means of communicative rationality between all actors (commercial stakeholders, residents, consumers, etc.). In 2060 all our vehicles will run on electricity from sustainable production sources, such as solar and wind. We will travel less and more efficiently in part by improving spatial proximity to (social) functions. To aid this mobility transition, biofuel potentials will be optimized to phase out the existing infrastructural dependencies by 2040. After which a complete build down from all polluting mobility fuels will be put into action. This phase allows different actors to cultivate and experiment with sustainable waste–to– value connections between stakeholders by optimizing biofuel potentials from regional waste. To make this transition succeed, the mobility and fuel transition is brought on through the three pillars: 1. sustainable connections, 2. waste to value and 3. consumer patterns. Allowing for an integrative transition in line with the global move towards a circular economy and a more healthy and liveable environment. As a result of this transition the petroleum–industry leaves waste spaces that require transformation. By creating a toolkit to assess different typological waste spaces, petrol stations, terminals and refineries will be transformed into residential, office, cultural, green and other functions after the soil is properly remediated.