A subfloor component includes a hardboard panel having first and second opposing faces and a plurality of intersecting grooves to define, in cross-section, a plurality of pedestals having walls that extend into the panel from the first face toward the second face. The subfloor component also includes a film of substantially moisture-impervious material attached to the first face of the panel and that conforms to the tops and walls of the pedestals and to the bottoms of the grooves.