Statistical Analysis of Wood Durability Data and Its Effect on a Standardised Classification Scheme

The biological durability of wood is an important property for outdoor applications of wood-based products. In temperate climate zones, the most critical biological hazard is wood-destroying fungi, and the European standard EN 350 in combination with EN 113-2 provide guidance on sampling, testing, and classifying wood durability against brown and white rot fungi. However, in their latest revised versions, both standards recommend the use of probability density functions for fitting mass loss data (ML). Subsequently, the durability of wood and its variability should be further characterised. The aim of this study was to statistically analyse the ML data from laboratory agar plate tests with different European-grown wood species and to examine the effect of different statistical treatments on the standardised classification scheme of wood durability. It was concluded that more precise guidance is needed on the sampling procedure since significant differences in durability exist between stem zones. The assignment of dispersion indicators requires a revision to ensure clear, unmistakable, and reproducible durability classification of wood. Deficits in the description of the proposed statistical treatments in both standards became evident. It can be questioned whether the application of probability density functions provides additional information about the variability of wood durability.