A simulation model was developed for three-dimensional heat and moisture transfer and viscoelastic hygrostress formation in a composite body undergoing drying. In the model the chemical potential of moisture in the body was used as a mass transfer potential since different materials had different affinities to moisture. The governing equations were solved numerically by a finite element method. The model was validated experimentally through drying experiments using triply layered brick shaped samples made of the hydrates of starch granules and of 3:1 mixture of starch granules and sucrose.