The renovation of old houses is gaining increasing significance. The extent of labor and costs depends mostly on the condition of the wooden ceilings. By means of structural endoscopy wooden ceilings can be investigated by non-destructive testing of their entire cross-sections. In this way the degree of degradation becomes evident at an early stage. Also, apart from visual judgment, specimens from interior wood sections can be collected with special tools. In contrast to the conventional detaching of parts of the flooring, the method of structural endoscopy can be carried out without disturbing the residents.