© 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.Polydimethylsiloxane (PDMS) and hydrophobic silica nanoparticles (HSNP) were applied to coat wood surfaces to decrease boron release from DOT (disodium octaborate tetrahydrate) treated wood. The surface-modified specimens were then subjected to a 14-day-leaching course followed by mold resistance tests under laboratory conditions. Water absorption, dimensional stability and water contact angle of the modified wood specimens were then determined. FTIR analysis and SEM imaging were also performed for characterization of the modified wood surfaces. Retention level of 3.3 kg/m3 was retained in the DOT and PDMS-treated wood specimens after the leaching process, but nearly no boron remained in the wood specimens treated with DOT only and DOT + HSNP. In accordance with leaching tests, the DOT and PDMS-treated specimens showed highest performance against mold fungi even after leaching tests; however, no complete protection was achieved in both DOT + HSNP and DOT-only treated specimens. The PDMS and HSNPs coated wood samples displayed water contact angles of 114° and 172°, respectively. The comparison of chemical, wetting and structural characteristics of the modified wood samples before and after leaching showed similar behavior. More detailed research is needed to obtain a better understanding of the mechanisms of interaction between PDMS/HSNP and wood surfaces.