Interventions on the Gothic Roof Structure of the Nave at the Lutheran Church in Bistriţa (Romania)

The roof structure of the Lutheran Church in Bistriţa is one of the historic roof structures with the widest span in Europe. With a volume of over 9,500 cubic metres, the span of the trusses is 22.60 m. The roof structure – built between 1557 and 1561 – underwent several consolidation interventions. It was seriously damaged in the fire of June 11, 2008, which entirely destroyed the tower’s roof structure and extended to the nave as well, in particular in the area next to the tower. The interventions treated those deficiencies of the nave roof structure resulting from the fire, or from defective maintenance and usage throughout time – missing parts, degraded joints, etc. – or from previous interventions, which altered the static model (by introducing straining devices on intermediary supports that were created subsequently). Made of 39 trusses (out of which 20 main and 19 secondary), the consolidated roof structure was restored as follows: at the first 8 trusses – where the fire destroyed over 70% of the parts – the initial structure was restored; at the consolidated trusses from 1897 (from truss #9 to truss #23), the static model resulting from consolidation was kept in the restoration process; whereas from truss #24 to truss #39 – consolidated in secondary trusses in 1926 – the initial static model was also restored.