In facilities management, decisions regarding how and when maintenance and rebuilding are to be carried out are made on a regular basis. Typically, there is a compromise regarding cost, usability and the possibility of exploring new options. Many case studies indicate that a large number of these decisions are based on simple models and that they are not adequately investigated. This is a problem, especially in cases of public procurement, where a high level of transparency in decision making is desired. There is a need for a proper decision basis in order to build a society that is economically, socially and environmentally sustainable. A working method is proposed as a tool for the integration of costs and benefits in decision making on investments in sustainable re-building. The guideline gives an overview as to why, when and how impact assessments and project appraisals can be conducted on different levels on a scale from tactical decisions to strategic decisions. The proposed method can be used to prioritise actions that need attention and to decide which preventive measures are the most efficient from an economic point of view. This paper explores the practical application of the guideline and presents an economic analysis and valuation in sustainable rebuilding management. Finally, the prerequisites for impact assessment and project appraisal and how they can be used and accepted by the users and decision-makers are discussed.