In the carrying out of non-destructive tests the following methods and devices were applied. In the case of the ultrasonic method the devices Tester CCT-4 and SYLVATEST were used. As regards the vibration methods natural frequencies of simple systems were measured. The devices used were accelerometers HOTTINGER, amplifiers of the signal and the osciloscopes GOULD.

Before the carrying out of non-destructive tests the structural timber was graded according to the standard EN 518. After the finishing of the non-destructive tests destructive tests were carried out according to the standard EN 408. These destructive tests were evaluated in detail according to the standard EN 384. Several sample sets from different localities of the Czech Republic were tested.

The aim of work is to contribute toward a deeper understanding of the problems of non-destructive timber grading and the determination of the performance of structural timber elements. Emphasis was laid on the choice of the non-destructive method and the testing procedure in view of achieving the most objective results concerning the strength and stiffness properties of timber.
Each of the non-destructive methods is also evaluated from the point of accuracy, as well as technical complexity and time of duration.