Lap-joint trials (following European Standard ENV 12037) were set up with 11 different softwood and hardwood species. The main aim was to evaluate the suitability of this test standard (developed for testing wood preservative effectiveness) for natural durability testing. The moisture development has been followed during a 36 months period. In this paper, the outcomes of different moisture contents evaluations are presented. Completely painted samples without a lap-joint have the lowest moisture content with an increasing maximum in moisture content in the winter period over the years, however for most timber species (but pine sapwood) still staying around 20%. The painted lap-joint samples have the highest moisture content with long periods above 30%-50% for most species. The moisture content of the lap-joints is predominantly influenced by the wood species. By applying a coating to the lap-joints, all species stay wet for longer periods (more than a year). For lap-joint trials without any coating, most of the (hardwood) species stay relatively dry for longer periods, not allowing any fungal decay. In general it can be concluded, that a lap-joint approach can contribute to natural durability testing, however the course of decay under mid-European climate is very slow for an accelerated method.

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