Roof drainage systems of historical buildings no longer serving effectively under existing conditions should be repaired according to maintenance programs developed specifically for them through a study of their characteristics, discharge capacities, faults and the climatic conditions prevailing in their environs. The studies necessary for this should ideally be done using non-destructive methods. Such a study was conducted on the roof of a 13th century stone monument, "Agzikarahan", in Aksaray, Turkey, to assess its overall drainage adequacy and its potential for taking corrective action. Results showed that the roof was originally configured to provide a proper peripheral drainage system. However, it fails at present due to earlier incorrect interventions and subsequent lack of maintenance. Suggestions were made on urgent remedial interventions, preventive measures and future improvements. (c) 2006 Elsevier Ltd. All rights reserved.