A model of the mechanical dewatering process during wet pressing was formulated that includes a non-uniform compaction at the interface between web and felt. This non-uniform compaction is assumed to be caused by the surface roughness of the felt. The model of the simultaneous deformation and flow in the fibre network was implemented in ABAQUS, a general finite element system. The dewatering behaviour of different rough permeable surfaces, representing model-felt surfaces, was investigated. Results obtained with the model showed the influence of the felt model surface on dewatering, especially at lower grammages. Here, the non-uniform compaction leads to a considerable decrease in obtained dryness. This decrease was more pronounced for rougher felts. In addition, each felt had an optimal dewatering behaviour at a certain grammage. In general, finer model felts performed better at lower grammage, which is in agreement with practical experiences in wet pressing.