Impregnation of dry wood with pure lactic acid oligomers (OLAs) followed by heat treatment confers promising properties to wood because of OLA's good diffusion, in-situ polymerization and persistence in cell walls. Treatment provides drastic reduction of the equilibrium moisture content, high dimensional stability and good durability. The presence of water during treatment has been evaluated. Curing of OLA impregnated dry wood in humid atmosphere leads to a strong and global degradation of the material. OLA treatment of wet wood only impacts the water leaching rate negatively. Treatment of dry wood with OLA diluted in water additionally decreases the biological resistance and is not efficient for decreasing hygroscopicity. Treatment of dry wood with lactic acid solution leads to a lower polymerization level but confers good properties.