EVALUATION OF HISTORICAL CONSTRUCTION TIM BER .1. DENSITY AND COMPRESSION STRENGTH

Structural timber, approximately 600 years old, was investigated durin g restoration work undertaken on the roof of St. Nicolai Church in Ber lin-Spandau. The objective was to check whether the original trusses, in particular the end pieces, partially damaged by bacteria and insect s, could be used for reconstruction. This was to be determined in dens ity and strength tests. Furthermore, new structural timber was also te sted for comparison with the old wood material. Annual ring widths pro vided no significant evaluation criteria. In the density/strength coll ectives the old wood material showed a tendency to deviate from the ru le that higher density values have a definite correlation with higher strength values. On account of the ageing process (resin formation, ce ll structure changes, loss of substance) it was found that the scatter ing range of test values increased. The average compression strength f or the undamaged old wood material achieved values which are within th e range of those for ''fresh'' wood.