Abstract: A foundation system, such as a frost-protected foundation system, includes an elongated body having a lower base surface, an upper support surface and side surfaces between the lower base surface and the upper support surface. The base surface is adapted to be supported on a ground surface and the upper support surface is adapted to supporting at least a portion of a structure. The body may be made substantially from a polymeric material, such as a high density crush resistant material, an extruded polystyrene insulation, or the like. At least one of said side surfaces is at an acute angle to said base surface. An architectural structure made with the frost-protected foundation system includes a slab supported with the upper support surface.