Abstract: A molding composition is disclosed for forming in a single step a natural sandwich foam product having a cellular core and a thick, densified outer layer. A hard, particulate filler material such as fly ash is admixed with an unreacted, rigid polyurethane foam system, together with a density distribution control agent such as carbon tetrachloride which lowers the viscosity of the admixture. In molding, the mold cavity is charged with the admixture and the foam reaction is permitted to occur with the mold closed. The resultant, filled foam product has a thick outer layer formed adjacent the mold surface of substantially greater density than its core. In the densified layer, both the polyurethane and filler material components of the resultant product are concentrated to provide over three times the density of the core structure. Formulations are set forth which provide substantial layer thickness and an outer surface having a durometer hardness value of 50 or greater over the entire surface area.