Testing the durability of timber above ground: evaluation of different test methods

A large number of studies on the decay performance of wood in outdoor exposure have been conducted in the past. However, no test methodology for wooden components exposed above ground reflecting the variety of different loads has been established so far. Many test protocols were modified in different ways throughout the years and results were often published only in an encoded or incomplete way. This makes it difficult to obtain comparable results to work on a comprehensive above-ground test methodology. Therefore, a comparative study on moisture performance and the resulting decay response was conducted. Five different wood species were exposed according to 24 different test methods representing a wide range of different exposure situations including in- and on-ground exposure. After three years of exposure the moisture load as well as decay development differed between the test methods and tested materials. Different parameters were identified influencing the moisture performance of wood in the respective test set-ups and finally an attempt was made to set up a test methodology providing sets of test methods for differently severe applications within use class 3.1 and 3.2 as defined in the European standard EN 335 (2013).