This work was focused on the experimental testing and finite element analysis (FEA) of timber beams with and without flaws (different types of cracks and hole). The aim was analysing the effect of flaws on their load-carrying capacity. This topic is important for designers of timber constructions, since even today there is still a lack of knowledge in the field of fracture mechanics of wood. The results from experimental testing and numerical simulations were discussed in this paper. Two wood products were analysed, namely, sawn and glued laminated beams (glulam beams) and three types of flaws were considered for both products i.e. a vertical crack, an oblique crack and a circular hole. In addition for glulam beams the horizontal crack in the glue line was considered. Four-point bending test was created for experimental testing considering quasi-brittle characteristic of wood. 4 samples for each type of beam, 36 in total. XFEM (Extended Finite Element Method) was used for finite element analysis of beams with considering orthotropic-elastic properties for glulam beams were considered and The results of mechanical tests and FEA gave us an overview on how different types of flaws influence the load-carrying capacity of sawn and glulam beams and with what accuracy we can simulate cracks in wood using computational method.