The potential of an architecture that combines old and new with partial interventions

"We cannot not build. It is about a balance", De Vylder says. "The 33.3% attitude offers a way of working that does not strive for a 100% solution, but rather seeks a partial yet precise intervention that bridges the gap between old and new." The Flemish architect has worked a lot in his homeland Belgium whose contemporary architecture is famous for intertwining old and new elements to form a new, strong expression. "In Belgium the scarcity of means drove our attitude", De Vylder say. In Switzerland it is the other way around. "Because there is so much money that needs to be invested the pressure is high to replace old structures completely."

The professor has developed the course together with the assistants Oliver Burch, Jakob Junghanss and Lukas Ryffel, who got to know each other at ETH Zurich and founded the architecture practice 8000.agency. They are part of the collective ZAS* that is currently teaching a visiting studio at D-ARCH. The three architects often deal with retrofitting the existing. In 2024 they published the brochure "Offen erschlossen: Ansätze zum Weiterbauen" that presents their findings from the BSA research grant on arcade accesses for existing structures.

A parking garage as a park

The book "Towards Transformation" by Triest explains the 33.3% approach and presents 22 student projects. The studio examined three contexts in the city of Zurich: real estate developments, the densification of the garden city in Schwamendingen and single-family neighborhoods. The students explored actual planned projects and altered them to highlight the potential of the existing. For example, a group of students kept the underground parking garage of an old structure that would have been abandoned and sealed and turned it into an underground park. The planned residential volumes could still be constructed on top.

A tricky part is how to deal with small houses that make up a lot of the building fabric in Switzerland. A group of students transformed a single-family house into a small housing cooperative with seven members. Another project extends single-family houses based on a series of agreements with the neighbors. At one site the students kept single-family houses but transferred the legal building reserves to a large housing development next to them. This allows to densify the city while keeping an open space between the single-family houses.

In Oerlikon a steel structure by the architect Jacques Schader is re-used by placing it on top of a concrete building next to it, making way for more densification without losing connection to history. The projects oscillate between past, present and future. "It is fascinating how young people want to learn this playful, creative attitude", says De Vylder. "They want to act differently, questioning the standard approach." However, the students did not ignore reality. Together with stakeholders such as pension funds, housing cooperatives or developers the studio also looked at the feasibility and the economic side of the interventions.

In recent years the idea of adaptive re-use got more attention in Switzerland thanks to climate protection efforts, concerns around building heritage and higher interest rates. "In many ways Switzerland is ideally suited to refurbish existing structure", the architect Oliver Burch says. "The construction quality is usually high and the maintenance thorough, so the buildings are in good condition to build upon."