Outdoor efficacy of additional hydrophobic treatment of weathered wood by siloxane

•Significant improving of hydrophobicity of weathered wood.•Effective is easy applied one layer of siloxanes treatment.•Applying of treatment in water solution with low concentration.•Treatment of weathered wood is more durable in comparison with native wood. Recently, the share of the use of untreated wood in exterior applications has been growing due to positive ecological and health impacts. In particular, facade elements, but also terraces, fences, gazebos, and other structures without contact with the ground can be made of untreated wood with moderate or lower natural durability against bio-damage. During exposure, however, there is a high increase in the water soaking into weathered surfaces. In terms of higher temperatures and more permanent precipitation, the risk of damage by wood-destroying fungi, which have a fatal impact on the functionality of wood products, increases significantly. This work is focused on the possibility of additional hydrophobization of weathered wood with siloxanes. In particular, samples of spruce pre-weathered for 3 and 5 years in an exterior exposition according to EN 927–3 were additionally treated by siloxane emulsion. For partial comparison, oak and larch were also weathered for 3 years, and native non-weathered references were also exposed. Moisture content during the subsequent 12 months of exposure was assessed, and changes in wetting contact angle, colour, roughness and changes in chemical composition by FTIR were analysed. Additionally, the ignition time of weathered samples was evaluated using a conic calorimeter. The results indicated a good possibility of using siloxanes for risk conditions threatening biotic degradation of weathered wood surfaces in outdoor conditions.