The Séquences Bois team choose this project for the challenge it exemplifies. Indeed, it reaches 38 meters high with 11 storeys totally built in timber, on a concrete basis. Devoid of concrete cores for the circulations, the difficulty was to withstand the sismic horizontal forces, 3 to 5 times stronger that the wind forces. Made up of 3 blocks standing on a continued three storeys basis, constructed with timber frame walls, the high storeys are built in glulam posts and beams, with peripheric structural walls in CLT, and, for the higher block, with CLT shear walls to brace the building. So the three more common building in timber methods are represented. Concerning the details, 80 % of the assemblies were realized by the inside with corner pieces. The floors are based on wall beams fixed by bonding to the walls.

The building, which mesures 100 meters long, is situated in Strasbourg, in a large urban project zone called Deux-Rives, once a brownfield site, where many timber buildings are being built (“l’ilôt bois”, that we could translate the “wood island”): “Sensations” is the first of them to be delivered.

The spatial configuration offers a double orientation to the most of the dwellings and each benefits from balconies.

Because the French scientific and technical building center (CSTB) ask for a fire propagation test on a prototype of the initially planned wood-clad façade, the architects finally replaced the glass insulation with a rock insulation, more resistant to high temperatures, and the wood cladding with steel to reduce the combustible mass. So the three first storeys above the varnished concrete are dressed of yellow cladding and coarse mesh expanded metal, and the higher storeys with dark panels and thin mesh expanded metal.

The client, Bouygues Immobilier, has count a 20% extra cost compared to concrete construction. The project lasted six years from the competition to the delivery, with only 3 months of executing the timber structure and the concrete basis.

Architect: KOZ Architectes, Paris

Wood engineering: Ingénierie Bois Illios

Wood construction company: Altibois

Delivery: 2019

Photo credits: Cécile Septet

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