This study relies on comparing the behavior of structural timber pieces in naturawith pieces treated with castor oil-based polyurethane resin, with regard to the resistance to axial compression. The treatment attempts to improve the mechanical behavior of the wood and, to this end, two species will be compared: Pinus and Eucalyptus. Evaluations will be carried out according to NBR7190(1997)aiming to characterize physical and mechanical properties of the pieces and the results will be submitted to the statistical analysis by the Anova and Linear Regression methods