In this paper single-sided nuclear magnetic resonance (NMR) is applied to characterize the moisture diffusivity of typical building materials subject to spontaneous imbibition. Three exemplary materials are investigated: ceramic brick, calcium silicate and autoclaved aerated concrete. Single sided NMR is engaged to determine the time development of moisture content at given positions in absorbing samples. Via mathematical procedure the time development of the moisture content is translated into the liquid water diffusivity function. This function is then used as input of a numerical solver to simulate the absorption process. The results are finally compared with water uptake curves determined gravimetrically and with data from the literature, proving that the applied method is reliable.