Addition of stories elementary school, Köniz

The project
The numbers speak for themselves: between 2013 and the end of 2015 alone, the number of students in the Buchsee-Köniz school district grew from 410 to 472. To create more space, the municipality decided to add one floor to each of two two-story wings of the elementary school. In addition to new classrooms, the new floors could also accommodate group and multi-purpose rooms as well as the school library. The existing buildings, built in the 1950s as a solid construction, had only limited load-bearing capacity. The new floors of wings C and D of the school building were therefore built entirely in timber frame construction in order to keep the loads low.

The construction
The new flat roof consists of a simple beam layer of glulam supported on cross beams. In order to be able to transfer the loads to the points determined by the structural engineer, a steel beam visible from the inside was inserted on the south side. The non-structural exposed aggregate concrete elements were cut out at the support points to properly transfer the loads from the columns to the existing concrete parapet. These columns rest on welded-together steel angles that were mounted to the concrete parapet and transfer the loads.

The challenge
For the new floors, the timber engineers also had to take into account the large shear forces that can be triggered by wind or earthquakes. This challenge was solved with a three-layer slab: This slab was nailed to the bracing wall at the top and connected to the concrete slab at the bottom with iron angles.