Fresh fish and fresh vegetables harvested directly from the roof, produced with treated wastewater from the building, that is the vision of ROOF WATER-FARM (RWF 2013-2017). Water-Farm technologies such as aquaponics and hydroponics as resource- and space-sensitive farming systems are at the focus of urban and infrastructural transformation processes towards the loop city. The project, funded by the German Ministry of education and research (BMBF) from 2013–2017, first-time investigates the link of these light-weight farm systems with technologies and modules of building-integrated water recycling. Besides the theoretical reflection of rainwater use, the hygienically-safe treatment and use of greywater (kitchen, bathroom) as service water for the production of fish and edible plants is investigated and tested on a practical level. In addition to, the project first time tested the production of an urban liquid fertilizer („goldwater“) out of blackwater (toilet) for an resource saving urban food production. Based on and via an upscaling process building studies and building passports are developed for conventional typologies such as residential buildings, educational buildings, hotels or commercial buildings. Networking maps envision the loop-oriented city transformation exemplary for distinct Berlin neighbourhoods from the inner-city, via the periphery to areas of transformation. The interdisciplinary handbook presents the main results of practical and planning-design work at the scales of technology, building, neighbourhood, and city as well as from the perspective of RWF actors and users. Literally „from the screw to the city scale“ it shows technological and urban design strategies linking decentralized wastewater and food production as multifunctional infrastructure of the loop city. A Toolbox offers additional materials and examples focussing topics such as operation & maintenance, feasibility or life-cycle assessment, upscaling and transferibility of the modular ROOF WATER-FARM approach. ROOF WATER-FARM communicates future city and infrastructure development to a broad audience suitable for daily-use. Complementary to the technologie showcase at the ROOF WATER-FARM pilot plant in Berlin-Kreuzberg, the handbook serves as inspiration and tool for the sustainable urban transformation facing urban water, food, multifunctional infrastructure and the loop city.