Various degrees of rot and other damages in ceiling beams with dimensions of 6500-8800 x 160-200 x 240-310 mm (length x height x width) situated in one historical bourgeois house in the UNESCO town Banská Štiavnica, Slovakia were determined visually and by the PUNDIT-plus ultrasonic device. Subsequently, for seventeen of the most bio-damaged fir (Abies alba Mill.) beams chosen for exchange were carried out other ultrasonic tests and also “in vitro” ultrasonic and bending tests on small specimens (300x20x20 mm). “In situ” measurements have shown that the lowest velocity of ultrasonic waves is usually in the ends of beams, i.e. in their direct contact with walls it was only 300-400 m/s, while 0.5-1 m from their ends it was usually higher from 700 to 1100 m/s. “In vitro” measurements (the modulus of elasticity determined either by ultrasonic test – Ed, or by bending test – E; the bending strength “modulus of rupture” – fm) depended significantly on the density of tested fir specimens. High correlations were observed also between values of the dynamic and static modulus of elasticity, and between values of the modulus of elasticity and values of the bending strength. Achieved “in situ” and “in vitro” results could help at evaluation of bio-damages in other wooden heritage structures, as well.

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