Felsenburg House in Biel is a renovation and vertical extension by Sara Gelibter Architecte for an artist couple. Initially planned as a modest refurbishment, the project became more ambitious after serious structural defects were uncovered, including a long-compromised roof. The solution was a new top floor that transformed the former industrial structure into a distinctive home.
House on top of a house
The building’s layered past shaped the intervention: once a wine shed, later industrial workshops, a youth hostel, and then fragmented into domestic conversions. Rather than erasing these traces, the design built on them, creating a “house on top of a house” that redefines the building’s identity while addressing noise and climate challenges from the adjacent railway. The result is a long-life, loose-fit, low-impact building—resourceful, adaptable, and rooted in its historic context.
Windows facing the tracks were closed, while large openings towards the Alps frame expansive views. Inside, salvaged elements such as a theatre staircase, reused beams, and repurposed components reflect a collaborative, resource-conscious approach.
Sustainability strategies
The project embraces low-carbon design through reuse, circularity, and modest interventions. By retaining the 19th-century timber frame and masonry, it avoided wholesale demolition and preserved embodied carbon as well as heritage. Where selective demolition was required, temporary timber structures were used, then dismantled and reintegrated on-site to maximise reuse and reduce waste.
The new timber structure was prefabricated off-site and installed in a single day by helicopter, then clad in lightweight fibre-cement panels for durability, noise protection, and future reuse—avoiding heavy road traffic near the railway.
Passive strategies include airtight detailing, compact insulation, and a south facade prepared for future photovoltaics. Corrugated fibre-cement cladding adds durability and noise protection. While uncertified, the project aligns with Minergie-Eco and SIA standards, reducing embodied and operational carbon.
Material innovations
The project maintains a commitment to sustainability through selective deconstruction and reuse: temporary timber was dismantled and reintegrated into a new truss system. Low-tech timber engineering with platform-frame infills and glulam beams reduced embodied carbon and allows for future disassembly.
Locally sourced materials include Swiss timber and wood-fibre insulation, balancing performance with low embodied carbon.
Surface economy was prioritised: exposed OSB walls and furniture eliminated multilayer finishes, thereby aligning with circular design principles. The reuse of existing foundations avoided further concrete and emissions.
Adaptive reuse principles
Adaptive reuse shaped the project's logic: preserve, extend, and prepare for reversibility. Modular timber portals allow flexible layouts, lightweight infills are replaceable, and the prefabricated roof can be dismantled in modules for long-term adaptability.
Self-building was central to the process: family and community dismantled, sorted, and reassembled materials. This reduced costs, increased reuse, and reinforced the home’s connection to its inhabitants.
