This paper has two parts: a) Analysis of construction techniques with load-bearing masonry of the buildings in the medieval town at different periods, focusing on the examination of structural performance through the passage of time in relation to the seismicity of the region and the special properties of building materials. b) Presentation of the operations of the Office from October 1985 till today. Analysis of the principles directing interventions in relation to structure and available materials. Detailed presentation of the methods used in the strengthening of load-bearing walls and stone vaulting (surface repair, reinforcement) and timber floors and roofs carried on timber beams (treatment-conservation, securing of their diaphragmatic function, construction of roof covering).