An ever-increasing population, urbanization and visions towards sustainable cities clarifies the need of densification. When densifying existing urban areas adding storeys could serve as a residential densification, which would also meet the market demand for centrally located apartments. An increased understanding of the potential of vertical densification gives way to the aim of this thesis to increase the amount of centrally located housing. This thesis provides knowledge of adding storeys and how property owners can identify opportunities in their existing building stock. The first question, What kind of residential densification takes place in Sweden today? highlights ways of residential densification; development of brownfields, infill and adding storeys, where adding storeys is what this thesis then focuses on. The result came through a literature review that also clarified important factors when adding storeys. This part of the literature review, a case study and interviews answers the second question, What factors are central when adding storeys? and accumulates the factors; culturally listed buildings, structure, year of construction, attic apartments, need of renovation, area potential, accessibility requirements, revenue ratio and 3D-property division. In an analysis an inventory instrument is designed based on the central factors. The inventory instrument is applied in an illustrating work on a property company's existing building stock. The result of the inventory answers the third question, How can a property owner examine the opportunities for residential densification through adding storeys on their existing building stock? and identifies five properties as possible for adding storeys, whereof two are highlighted as best suited. Furthermore, in the third and final question a description is given of a continued deepening process. For densification to occur at the right place and in the right way, it is not only the existing building and its load-bearing capacity that is to be assessed. The thesis main conclusion is that the context and environment of the existing building are of equal relevance.