Wood in outdoor applications is subject to various decomposition factors. Wood degradation can be prevented by construction details, biocide protection of wood, wood modification, or selection of naturally durable wood species. Unfortunately, the majority of timber species in Europe do not have naturally durable wood. Imported tree species represent a new pool from which we can draw wood species with better natural durability. Wood performance in the outdoor application is a function of biologically active compounds (extractives) and water exclusion efficacy. Based on these parameters, we can estimate the resistance dose that reflects the material property of wood. Recently, the model most commonly used for this purpose is Meyer-Veltrup. Literature data indicate that the durability of the wood from native and new sites is not always comparable, so it is necessary to determine the resistance of non-native wood species from new sites. This paper presents original data on the overall wood durability of American Douglas fir (Pseudotsuga menziesii) and Sitka (Picea sitchensis). Experimental data show that the adult heartwood of Douglas fir is more durable than the wood of European larch (Larix decidua), and Sitka spruce is more durable than the wood of Norway spruce (Picea abies). Among the wood species considered, the wood of the American Douglas fir shows the greatest potential for outdoor use.

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