A grand tower project west of Lausanne has taken a new step this week: the Tilia tower in Prélie-Male, which will dominate a district along with 4 other buildings, the public investigation of which began on Wednesday. 85 meters high for 27 floors, it will be made of wood and concrete.

>> Read: A 27-story tower in Prali (VD) must see daylight

Not far away, the construction of the Mali Pharae Tower will begin this year. Slightly smaller – 60 meters for 14 storeys – the tower is presented as the first wooden structure tower in Switzerland.

“It is a challenge. We are not used to facing such a challenge in the wild and we are happy to tackle it,” explains in the forum Matilda Benoist. He is a wood construction engineer at JPF-Ducret and participated in the design of the Malley Phare tower.

mix between concrete and wood

She points out that wood does not impose a height limit. “It’s all about good design, wood can achieve feats. You just have to keep in mind that compared to concrete, it’s not always super relevant. You can’t just copy and paste large concrete constructions And can switch it to wood. You really have to think about the project that it’s wood and do everything to make it work.”

You can’t just cut and stick large concrete buildings to wood

Matilda Benoist specifies that concrete is also used in timber construction: “For acoustic reasons, we often prefer to have mass. So on our tower project, we use composite slabs instead. Wood-concrete , with wooden joists and a fairly thin concrete slab, which provides just a little bit of mass.”

Wooden towers are lighter than towers made only of concrete. But the engineer makes sure it is as solid as possible. “For a given load, we shape all of our elements like we would with concrete or metal.”

What is the risk in encountering a fire?

Regarding fire risk, Matilda Benoist explains that wood is not a problem: “Wood, when it burns, forms a layer of carbonization around it that helps protect and maintain a healthy inner section. And as engineers, we calculate this healthy section so that it can resist a substantial amount of time during a fire.”

>> Read: No offense to the three little pigs, a test proves that wooden houses are solid

Matilda Benoist also specifies that timber constructions tend to have no less longevity than other structures. In contrast, “we have been building with wood for hundreds of years, we still have many buildings across Europe that can show that as long as wood is used in the right place, with good projects, there is no longevity.” It’s not an issue.” And to conclude: “What is needed to protect the wood from changes in moisture.”

Radio Interview: Pietro Bougain

Web text: Antoine Schaub