Composite materials based on scrap tires and polyurethane type polymer binder with defined reactivity were investigated to underline the influence of water (varying air humidity, special treatment of rubber crumb with water) during the production on selected mechanical properties. Compressive stress and modulus of elasticity E at 10% deformation, Shore C hardness and apparent density were investigated. Strong correlation between the above-mentioned mechanical properties of the composite materials and the crosslinking conditions of the polymer (presence of water during the production of composite materials) were observed. It has been confirmed previously that the crosslinking degree of polyurethane type binder separately and, therefore, at the same time mechanical properties of binder was strongly dependent on water as a significant factor during the hardening of the polymer.