The building has been built in 1964 and is rectangular in plan with dimensions 44.84x12.60m with a prestressed concrete structural system. It has 9 storeys and a basement. Its initial design results in a very torsional sensitive building since it is a high slender building with only some structural walls which are one main core and some side walls which have only been constructed in the upperstoreys and not the ground and underground floor. The intervention, after the examination of 5 different variations, is the addition of a new core in order to reduce the torsional sensitivity and the strengthening of the structural elements that do not fulfill the capacity checks.