The Lutheran Church A. C. in Bistriţa, dating back to the 14th century, suffered major transformations between 1559 and 1563, which were performed by Petrus ITALUS de Lugano, a well-known craftsman, who carried out many exceptional interventions in 16th century Central Europe. On the occasion of the 450th anniversary of the church’s re-sanctification (in 2013) – subsequent to the Renaissance transformations brought by Petrus ITALUS – the vaulted roof slab was conserved, through both consolidation works and enhancement of the Renaissance decorative painting, which was discovered during the building archaeology study prior to the consolidation interventions. The vaulted roof slab covers both the nave and the chancel of the church, and is built of brick masonry. The vault caps are supported by ribs made of 4-5 centimetre thick burnt clay voussoirs that are laid out perpendicularly on the longitudinal direction of the ribs, integrated in the masonry of the caps, with a geometry that shapes in a longitudinal direction the profile of the ribs. The ribs are made up of four types of voussoirs, according to strict rules. Some of the voussoirs gave way in operation and were locally replaced with gypsum longitudinal elements, which were anchored to the cap by metal elements. Other deteriorations in operation were caused by the flooding of the roof slab during the 2008 fire extinction operation, which led to the destruction of the roof structures of the tower and of the nave in the area adjacent to the tower. In order to replace the gypsum rib elements and the broken ceramic voussoirs, which were macerated, four types of ceramic voussoirs were ordered and integrated in the vaulted slab. The quality of the interventions was locally tested by in situ trials, consisting in overloading the ribs. The caps of the vaulted slabs were rehabilitated too, as reweaving and matting interventions were necessary each time cracks occurred in operation because of implementation technological errors. The presence of decorative paintings made the interventions more difficult, as these paintings were conserved
simultaneously with the consolidation works.
This article presents the whole intervention process, focusing on mechanical and technological aspects that are specific to exceptional load-bearing structures.
Keywords: vaulted roof slab, nave, chancel, rib, ceramic voussoir, mural painting