Resistance of pine and spruce against decay – The effect of wood chemical composition and coating with water-borne wood oil product

Natural durability of wood has been widely studied, but the combination of the natural durability and different treatments has not been the focus of many studies. The durability of wooden products is mainly based on the water permeability and the resistance against organisms. In this study, the water absorption and decay resistance of sapwood and heartwood of Scots pine and Norway spruce were examined. The effects of the wood origin and the coating with water-borne wood oil were also observed. The wood oil is penetrating treatment which is recommended for decking and garden furniture. The results were compared to the chemical composition of wood. The water absorption of untreated pine sapwood was significantly higher than that of pine heartwood or spruce. Decay resistance of pine heartwood was relatively high. However, the decay resistance was widely varied among different pine heartwood samples and in some cases this variation was significantly higher than that of pine sapwood or spruce. The effect of wood oil coating on decay resistance of pine heartwood was more significant than on pine sapwood. Elevated decay resistance was also found among coated spruce samples, but no significant difference between sap and heartwood was found. Decay resistance was comparable with water permeability and pinosylvin content of wood.