Portland brownstone is a widely used building material that is susceptible to severe deterioration from weathering. This type of stone contains expansive clay minerals that may cause damage during wetting/drying cycles. Water repellent treatments could, in principle, reduce this problem. The study presents results obtained from water vapor transmission tests, sorption isotherms, and hygric linear expansion of Portland brownstone treated with two types of water repellent, water based Siloxane PD and solvent based Natural Stone. The treatments were applied at two different moisture contents of the stone samples. The results obtained from the various tests showed no significant differences between the treated and control samples by overall statistical data analysis. The water based water repellent treated samples showed that those treated at lower moisture content adsorbed less moisture than those conditioned at higher one, and furthermore, they appeared to adsorb less moisture than the controls. Also the hygroscopic swelling showed no significant difference with the controls. However, the hygroscopic swelling of the sandstone was significantly modified by the solvent based water repellent. This water repellent had the opposite behavior to that of the water based one, the samples treated at a lower moisture content adsorbed more moisture than those treated at a higher one.