EUROPEAN HISTORIC ROOF STRUCTURES: CONCEPTS OF COMPOSITION AND INTERVENTION

Historic roof structures - load-bearing structure sub-units meant to ensure the roof covering's support - built for over two millennia throughout Europe, predominantly until the second half of the 19th century, based on empirical-intuitive concepts, from historical materials (hardwood or softwood, wrought iron, etc.), using traditional technologies, preserved in tens of millions of specimens, represent special heritage values, the protection of which is one of the major tasks of those who manage the conservation of the built cultural heritage's technical area. This paper presents the empirical-intuitive concept of European historic roof structures, which can be divided into frames (on purlins and on rafters and tie-beams, the latter group being split into two broad categories: structures on purlins and on collar beams), highlighting based on the structural analysis supported by mathematical modelling - the mechanical behaviour (Romanesque, Gothic, Baroque and Eclectic) of these load-bearing structure sub-units, also emphasising the heritage values that they own or carry. It also presents the characteristic deficiencies of the various categories of European historic roof structures (mainly caused by conditions of building mechanics, biology and physics, of soil mechanics and of building services) and the ways in which they can be intervened on during the course of exploitation, detailing the conditions in which we use the well-known rehabilitation methods: preservation, conservation, renewal and reconstruction. The theoretical study is exemplified through the more than 700 year old thesaurus of Transylvanian historic roof structures, which is currently in course of inventorying and conservation.