The sorption and transport of water in two porous building materials, clay brick and autoclaved aerated concrete, was studied in detail. The evolution of the distribution of liquid in the porous medium was analysed in terms of the Boltzmann transform method and anomalous diffusion equation proposed by Küntz and Lavallée . The apparent moisture diffusion coefficients of water were determined from the total water profiles using a modified Boltzmann-Matano analysis, and a good agreement with literature values was found. The application of anomalous diffusion model to building materials indicates that the previous 1/ 2 t relation is not entirely accurate to estimate the volume of absorbed water. This result has particular relevance for evaluating the durability of building structures.