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Elevated Living Above Active Railways with Mixed-Use Spaces

Authors:
Walter Hjaltested, Caterina Decker
Elevated Living Above Active Railways with Mixed-Use Spaces
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Located above active railway viaducts, the design transforms underutilized infrastructure into a dynamic mixed-use environment with diverse housing options and integrated community spaces.
5 key facts about this project
01
Located above active railway tracks, enhancing urban use of infrastructure.
02
Design includes circular public squares encouraging social interaction.
03
Mixed-use floors accommodate both residential and community facilities.
04
Potential for over 250,000 new homes without requiring additional land.
05
Varied apartment typologies cater to a wide demographic range.

The City in the Sky project makes use of the Greenwich Railway Tracks in London, addressing the city's high demand for housing while enhancing community connections. The design combines residential and commercial spaces in a multi-level urban structure that seeks to foster interaction and accessibility among residents.

Design Concept

The architectural layout reimagines the railway viaducts, which have primarily functioned as storage and maintenance areas, turning them into a lively mixed-use environment. Comprised of a two-story, low-rise structure, the project spans about 5 kilometers, creating a continuous living area that features streets elevated above the ground. This approach aims to connect individual living and working needs with broader community experiences.

Programmatic Elements

Mixed-use floors within the City in the Sky include both living units and community facilities such as kindergartens and workspace offices. This design provides vital services for residents and serves as a sound-insulating buffer between the apartments and active train operations below. By integrating various activities within the same space, the environment promotes a vibrant atmosphere where daily life and work can coexist.

Community Interaction

Pedestrian paths and public squares are woven throughout the design, facilitating movement and fostering social connections among residents. Circular public spaces feature restaurants and cafes, encouraging community engagement and enhancing urban life. These areas contribute to a livelier atmosphere, breaking down the usual barriers often found in city designs.

Housing Capacity

The plan can accommodate over 250,000 new homes without needing to acquire additional land, presenting a sustainable approach to urban development. By offering diverse apartment types, from affordable units to more premium residences, the project meets the varying needs of a dense population. This inclusivity is essential in addressing the ongoing housing crisis in the city.

The City in the Sky concludes with communal spaces that encourage exploration and connection, framed by an inviting streetscape that serves as a gathering point for residents.

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The Next House: USA — A Global Call to Reimagine the American Suburb

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Competition organisers

Buildner is launching The Next House: USA, a global architecture competition that challenges architects, designers, and thinkers to reimagine the American suburban home for the 21st century. For decades, the suburban house has symbolized comfort and stability, but today it often reflects excess, isolation, and environmental strain. This competition asks: how can the American home evolve to address climate urgency, economic pressures, and shifting social values?

Participants are tasked with designing a prototype home of no more than 1,500 sq ft (≈140 m²) for a household of two adults and one child. The design should be compact yet generous, adaptable, sustainable, affordable, and replicable across diverse U.S. contexts. More than a design exercise, the competition aims to spark a conversation about how homes can support healthier, smarter, and more connected communities.

The total prize fund is $20,000 USD. The final registration deadline is May 20, 2026, and winners will be announced on September 22, 2026. The Next House: USA invites architects, students, and visionaries worldwide to redefine what the American home means today—and what it should mean tomorrow.

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