This existing building is a concrete and steel office building from 1960 with a total of seven floors, the first of which are shop premises. The planned extension is for the purpose of increasing office space. It has been concluded that it is possible to build on two full office floors as well as an enclosed technical floor. For our proposal we considered load-bearing structures in traditional steel and concrete, as well as with glulam and girder beams in wood. We found the wooden solution to be the cheapest and fastest both in material cost and assembly.