Purpose: With the vast changes in the work life comes changes in the office design. One of the newest on the market is ABW (Activity Based Workplace), were the employees themselves chooses were to sit in the office depending on what fits them best according to the moment. This thesis contributes with knowledge that is necessary for an organisation to know before they begin using an ABW. The goal is to evaluate how an efficient ABW-environment is created. An ABW are efficient when the workplace concept works the way it is supposed to do and with that provides good results from the recourses that are available. This thesis addresses the implementation of the transition to an ABW from a traditional office type and how the office design could look from evidence-based results. Method: The main strategy for this thesis is a case study that involves the organisation NCC. That is because the evidence-based design is based on their workforce and their office building. The thesis goal is achieved through four different data collection methods: literature study, interview, observation and guidance form an architect. These methods were chosen to gather both qualitative and quantitatively data. Findings: The findings are divided into three areas: the first question of issue presents the different office types performances, there are both advantages and disadvantages with all office types. The advantages that can be found in these office types is for instance the cell offices privacy, the open landscapes interaction possibilities and that the kombi office retain the social environment whilst still give privacy from other employees. Whereas availability and flexibility are the most significant advantage of an ABW. Some disadvantages are how cell offices can be unwelcoming, the open landscapes noise level and the fact that you can not work in teams in a kombi office. The second finding is the evidence-based office design proposal, from an efficiency point of view. A collocation of the factors that needs to be thought of when designing an ABW is the fundament of this proposition. Some of these factors are for example the possibility to privacy, have co-workers nearby and distinct zone divisions. The third finding of the thesis demonstrate an evaluation of the transition to an ABW. An evaluation has shown to be necessary when establishing an efficient ABW. One of the most important part is to understand the employees, meet their needs and let them be heard. Implication: It takes both well planned transition and good design for an ABW to preform efficiently. Design and efficiency depend on each other and there are a few distinguished factors of what makes a workplace environment efficient. When talking about the transition to an ABW it is important to have a substantial process were the employees are given the possibility to be involved and informed of the ABW-concept and its impact. Limitations: The main limitations of this thesis are from a design perspective, such as artificial lightning, technical equipment and ventilation. The focus instead lies with the placement of walls and rooms, as well as furnishing. The economy aspect is also something that has not been taken into consideration, either when designing or in the evaluation process. This is maintained by defining the searches and stay focused.