In this paper we investigate the influence of microheterogeneity on the phenomenological macroscopic material properties. The material analysed is Savonnieres: a French layered oolitic limestone. Due to the complex microstructure of the material the moisture permeability cannot uniquely be determined based on indirect measurement data. To overcome this problem we present an upscaling technique based on the modelling of transport phenomena on the mesoscale. The technique allows to determine an equivalent macroscopic permeability based on the geometric configuration and the permeability of the composing constituents.