Outdoor wood is exposed to biotic and abiotic degradation factors. In nature, these processes are desirable, but when wood is used for economic purposes, these processes needs to be slowed as much as possible. If the wood is not properly installed or protected, it can degrade in a short time due to fungi. Railway sleeper protection is one of the oldest wood protection applications. In the past, creosote oil was predominately used to protect railway sleepers. Due to environmental issues, creosote oil will be removed from the market sooner or later. Therefore, alternatives have to be developed. Some of the possible alternative are copper based preservatives. The thesis addresses the degradation, remaining concentration of copper active ingredients and relevant mechanical properties of railway sleepers impregnated with copper-ethanolamine solutions that were exposed in outdoor conditions for four years. There were no detectable signs of fungal degradation observed on beech sleepers if the sleepers are impregnated with preservative solution in a higher concentration.