We study the dynamics of spontaneously spreading drops of viscous liquids on top of porous medium made by non-interconnected pores. A model for the single pore case is proposed on a theoretical basis and validated by molecular dynamics simulations. The generalization to the multiple non-interconnected pore cases allows unique characterization of the dynamics of spreading on a porous surface by essentially two parameters referring to the size of the considered pores and the friction between the liquid and the considered surfaces.