Wood is inherently hygroscopic and will sorb moisture either directly from the atmosphere or via capillary action. Moisture can have marked effects on wood properties and repeated wetting and drying creates dimensional changes that lead to physical damage. Exposure to elevated moisture levels also increases the risk of fungal attack.

Wood preservatives have long been used to minimize the risk of fungal attack, but general concerns about all chemicals have encouraged exploration of alternative protection strategies, including water repellents that help keep moisture conditions below those required for fungal attack. The potential for a commercial water repellent to limit moisture uptake and dimensional changes was evaluated on Tasmanian shining gum (Eucalyptus nitens), messmate (E. obliqua), and southern blue gum (E. globulus) with prolonged water immersion. In general, dipping samples in the water repellent produced no noticeable improvement on either moisture uptake or dimensional change over 512 hours of immersion; however, moisture uptake in all wood samples was very slow and limited to the outer 5 mm of the sections. The results are discussed with specific reference to the use of these species in above ground applications with minimal preservative treatment.