Modern games often feature highly detailed urban environments. However, buildings are typically represented only by their facade, because of the excessive costs it would entail to model all building interiors of a city by hand. Although there exist automated procedural techniques for building interiors, their application is to date limited. One of the reasons for this is because designers have too little control over the resulting room topology. Furthermore, generated floor plans do not always adhere to the necessary consistency constraints, such as reachability and connectivity. In this paper, we propose a novel and flexible technique for generating procedural floor plans subject to userdefined constraints We demonstrate its versatility, by showing generated floor plans for different classes of buildings, some of which consist of serveral connected floors. It is concluded that this method results in plausible floor plans, over which a designer has control by defining functional constraints. Furthermore, the method is efficient and easy to implement and integrated into the larger context of procedural modeling of urban environments.