The respective tests consisted in glueing birch wood with urea-formaldehyde glue, F*l2*sM*l2*s glue and Wikol glue. The glued wood samples were modified with polystyrene, methyl polymethacrylate and Polimal-105 polyester resin. The material prepared in such a way was tested for dry shear strength after 6 hours of boiling and after 24, 48, 144 and 288 hours of soaking in cold water. The test results have proved that the wood glued with water-proof and semi-waterproof glues can be modified, since the strength of joints remains unchanged after modification. The best results have been obtained for the samples modified with polystyrene.