Weathering of stone materials in urban settings causes significant damage to heritage buildings due to the effects of air pollution and other factors related to the building environment (water transfer, interaction with binders, etc.). The assessment of weathering of rock surfaces requires the use of high resolution techniques, and this task is even more difficult if relatively short periods of time are considered. We explored the joint use of elemental chemical analysis, mercury intrusion porosimetry, and multifractal analysis of pore size distributions (PSDs) to assess the surface weathering of a granite rock widely used in the built heritage in NW Spain. The scaling properties of all PSDs obtained by mercury injection porosimetry could be fitted reasonably well with multifractal models. Generalized dimension spectrum, Dq, lead to a better definition of multifractal scaling than singularity spectrum, f(α) versus α. Statistical analysis shows a weak association of weathering with building age considering some chemical elements and several multifractal parameters. Building age has a tendency to decrease Al2O3, P2O3, D−10, (D−10–D10), and α0, while it suggest building age has a tendency to increase MnO, Cl, SO3, D1, D2, and D10. Our results show that multifractal analysis of PSDs may be an appropriate tool for rock pore size distribution and also a suitable indicator for assessing weathering.