In the frame of a scientific cooperation within the Swedish research program ‘WoodBuild’ comparative field and laboratory durability studies have been carried out by the Technical Research Institute of Sweden SP and Leibniz University Hannover. One objective was to improve test methods as well as evaluation systems in order to facilitate the use of (field) testing for service life prediction. Therefore field trials containing long-term moisture and temperature recordings were set up to verify the suitability of different test methods for estimating the durability of wood under different exposure conditions. In this paper the test set up as well as preliminary results of the comparative studies on moisture performance of different materials in standardized and non-standardized field tests are presented. The field trials include graveyard, double layer, sandwich as well as lap-joint tests, which were performed with natural durable, modified and preservative treated timber. To consider the aspect that different climate conditions affect wood degrading processes the tests were carried out at three different test sites: Borås (Sweden), Hilo (Hawaii, USA) and Hannover (Germany). In addition, different laboratory decay and moisture uptake tests were conducted on samples matched to the field specimens. Preliminary results of the continuous moisture content (MC) measurements pointed on differences in moisture load between test methods, materials, and test sites. A more detailed understanding of the respective moisture regime can be expected when using different above ground test methods. Compared to traditional durability field testing the moisture performance based testing allows for reducing exposure intervals and more use-class related assessment. Due to this it seems worthwhile to quantify further test methods related to their severity and consequently to different exposure situations. The results for the different modified and preservative treated timber products pointed on the need for determination of material-dependent critical MC.

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