Beech wood is amongst the most important wood species in Slovenia. The EU standard EN 350-2 classifies beech wood into the group of the least durable wood species. This is one of the most important reasons which limit the use of beech wood in outdoor applications. The majority of the data about beech wood durability is a result of laboratory tests as there were limited numbers of field tests performed. As the service life of wood significantly depends on the local climate conditions, this data cannot be simply copied from other countries. Therefore, field tests have been running at the field test site of the Department of Wood Science and Technology for several years now to determine comprehensive performance of most important Slovenian wood species including beech wood. Majority of the tests are performed in use class 3 applications (above ground, not covered). The first signs of decay on beech wood are visible after few months of exposure. Afterwards the decay proceeds and the samples are degraded between 4 and 6 years of exposure. The most important reasons for insufficient outdoor performance of beech wood are lack of biologically active extractives and low water exclusion efficacy. In order to elucidate this phenomenon moisture content was continuously monitored for 15 months. We believe that the field tests performed will lead us to the data which will enable better understanding of the phenomena of durability and improve durability of beech wood with state of the art modification solutions.