Extending the Life of High-Tech Façades with Digital Fabrication

NCCR DFAB researchers at ETH Zurich are investigating the use of Wire-and-Arc Additive Manufacturing to repair complex metal façades from the late 20th century. Using a historic building on the ETH campus as a case study, the team developed a digital workflow that includes reverse engineering, 3D modeling, fabrication, and structural testing to produce bespoke steel components to repair and conserve High-Tech facade constructions.

WAAM component. Image by Matthias Brenner.

The study focuses on a research building completed in 1998 on the ETH Campus in Zurich. Its multi-layered metal façade is both visually distinctive and functional, providing sun protection for the interior. The façade was built using components custom-made for this building, which are no longer available as spare parts, and detailed construction plans are missing. As a result, even small damages of the façade can make repairs difficult and may, in the worst case, require entire sections or even the entire system to be replaced.

Building Metal Components Layer by Layer

To address this challenge, the research team used Wire-and-Arc Additive Manufacturing (WAAM), a form of digital fabrication that builds metal components layer by layer, depositing material only where it is needed. This allows precise replication of bespoke elements while minimizing material use. The workflow begins with reverse engineering: 3D scanning and photogrammetry produce accurate digital models of the existing components. These models then guide the WAAM process to fabricate the replacement parts, which are subsequently tested to ensure they meet structural requirements.

Technical Testing of the Fabricated Bars

A particular focus was the steel eye bar, a connection element that carries structural loads in the façade system. Eight specimens were produced and tested, four under tension and four under compression. Tests show that the WAAM-fabricated bars perform reliably under real-world conditions, remaining ductile under load and easily exceeding the strength required for the façade. The specimens underwent additional porosity analysis, confirming consistent material quality. Overall, the experiments demonstrated that WAAM components meet engineering standards and are reliable for practical use in façade repair.

The specimen is tested for structural integrity. Image by Matthias Brenner.

Preserving Knowledge Embedded in the Original Construction

Beyond the technical results, the study highlights wider implications for sustainability and heritage preservation. Many façades from the second half of the 20th century, often combining metal and glass, are increasingly at risk. They use materials and construction methods that were innovative at the time, and replacement solutions are rarely available. Premature replacement not only wastes material and energy but also results in the loss of building culture and the architectural knowledge embedded in the original construction.

WAAM enables repairs to be made component by component, producing bespoke parts on demand that fit the existing structure. This reduces waste, avoids unnecessary energy use, and preserves the building’s character. By combining digital modeling, precise material deposition, and structural testing, the technology offers a practical, sustainable method for extending the life of high-tech buildings while respecting their historical and architectural significance.

This article is based on the paper “Structural behavior of a wire arc additively manufactured steel eye bar for the repair of a historic high-tech facade” by Matthias Brenner et al.

The project was made possible through an interdisciplinary collaboration of researchers from three different departments of ETH Zurich, combining architecture, mechanical, and civil engineering. Collaborators and co-authors of this paper are Vlad-Alexandru Silvestru, Patrick Studer, Thomas Denoreaz, Markus Bambach, Andreas Taras, and Silke Langenberg.

NCCR DFAB researcher Matthias Brenner, lead author of the paper on WAAM‑based façade repair, was featured on this webpage in 2024 during an earlier stage of this project. The article, “In the spirit of high‑tech architecture: digital fabrication”, provides additional context on the development of the research and includes a video interview with Matthias Brenner discussing the potential of digital fabrication for maintaining and repairing complex façades. You can read and view the article and video here: https://dfab.ch/news/in-the-spirit-of-high-tech-architecture-digital-fabrication.