Performance of European Wood Species in Above Ground Situations After 10 Years of Weathering: Evidence of a Positive Impact of Proper Design

Abstract

Most of European native wood species used outdoors are expected to last less than 10 years if left untreated and exposed to severe environmental conditions such as high humidity and biological agents. However, the current classification of wood’s natural durability based on EN standards does not fully reflect real end-use conditions, often underestimating wood’s performance in use. In addition, the importance of design details and the role they play in enhancing service life, especially in the case of outdoor applications, is often neglected. With the aim of evaluating the positive impact of proper design on wood’s service life, large-scale experimental devices, manufactured according to different designs (water draining / trapping) from six native wood species, were installed in 2009 in two French cities benefiting from different climatic conditions (oceanic / continental). The results of the evaluation carried out after 10 years of natural weathering demonstrated that (1) significant differences in the ability to withstand decay over time exist depending on the selected design details and the climatic conditions encountered in the experimental fields; (2) high variability in the resistance of non-durable spruce and poplar wood against fungal decay was noticed for each tested design, but with an unexpected high percentage of elements performing very well; (3) the moderately durable heartwood of larch, maritime pine and Douglas fir was mostly unaffected by decay even under severe conditions of exposure to rain (decking modules), suggesting these species may have greater value for outdoor applications without any preservative biocidal treatment than previously assumed.

Full document