Applications and Performance International joint field trial on the moisture performance of wood – Set up and first results

Wood durability to decay stems from its inherent resistance to fungi resistance to fungi. In this regard, wood's ability to withstand moisture uptake plays an important role as the lower threshold for wood decay is a moisture content of 25%. However, the aspect of moisture resistance is not yet sufficiently emphasized as a durability factor, both in the assessment of durability as a material property and within the context of durability-focused design principles. This international joint field trial was designed to provide a comprehensive comparison of different laboratory-based test variables and their potential for predicting the outdoor moisture performance of wooden elements over time at climatically different locations. Nineteen research groups representing 15 different countries from six continents teamed up to conduct field exposure tests and record wood moisture content over time. These results were then compared with more controlled moisture uptake and release tests in laboratory. Several of the latter tests showed a strong ability to predict moisture performance of exposed wood specimens under varying climatic conditions. The results should support the development of methods for incorporating ‘moisture performance’ of wood into existing durability classifications. Simultaneous exposure of matched test specimens under several climatically different conditions facilitated the development of a multi-year time series in just a few months. The approach might be considered for future projects to reduce the time frame for developing relevant data.