A radiant heating system comprises a thermally sprayed resistive heating layer bonded to an underlayment building material substrate. The substrate can comprise a sub-flooring material and the heating system can comprise a radiant floor heating system. The resistive heating layer can be thermally sprayed directly onto a sub-floor or similar underlayment material, including a cementitious backing material or a sound reduction board. A finished floor surface, such as a tile, wood or laminate surface, can be provided over the substrate and thermally sprayed heater to provide a radiant floor heater. In other embodiments, a radiant heating system includes a thermally sprayed heater bonded to a flooring overlay, such as a laminate board, to a heater insert, such as a flexible polymer film or a mica-based material, or to a concrete substrate. Methods of fabricating radiant heating systems include thermally-spraying a resistive material on a sub-floor or flooring overlay.