This paper reports attempts to optimise the chemical modification of wood impregnated with polybutylene succinate oligomers (OBS). OBS impregnation at temperature and subsequent heating to induce in-situ polymerisation led to high OBS uptake, but limited dimensional stability. However, subsequent water soaking followed by drying enhances wood dimensional stability in both high humidity environments and in liquid water. To enhance OBS treatment and performance, it was found that OBS impregnation followed by wet heat or water soaking and a second heating step, promoted oligomer migration into wood cell walls. These combined treatments provided modified wood with anti-swelling efficiency at 95% relative humidity (ASE*95%RH) values of 55–70%.