The object of this investigation regarding wood windows was to determine the types of damage which occur and to find the causes of damage due to decay. Another aim was to draw up recommendations for the repair of damaged windows and for preventive maintenance of windows which are likely to be exposed to decay. Work on the project, carried out jointly by the Swedish Forest Products Research Institute and Chalmers University of Technology, Gothenburg, commenced by an inspection of damaged windows The inspections covered about 40 buildings