In the present paper a probabilistic approach for modelling the tensile strength and tensile stiffness properties of timber boards and finger joint connections is presented. The approach includes the geometrical setup of timber boards (the position of knot clusters) and a hierarchical representation of two strength and stiffness related indicators. One indicator to describe the mean material properties of timber boards and one indicator to describe the lengthwise variability due to knots. Based on the two indicators the tensile strength and tensile stiffness of timber board sections and finger joint connections are estimated using material models. The application of the approach is illustrated. For this purpose, finger joint connections and timber boards with different length are simulated and the material properties are compared with values proposed in the literature.