Obsolescence is a serious threat for built property. As an often used demolition motive, obsolescence can be regarded as the last phase of the life span of buildings. From a sustainable viewpoint, life cycle extension is necessary to minimize waste. But there are more considerations to carefully maintain the existing stock. Knowledge about the prevention, the diagnosis and the treatment of obsolescence is therefor of growing importance. In previous research publications we combined the available knowledge about obsolescence in a conceptual model for further research on and appliance in the decision making about demolition. Since evidence based theoretical research references on obsolescence are scarce rare, the model has inevitably an explorative character. As the next step in our research, this paper describes the outcomes of a series of case studies to test and further develop the model.