Abstract: A composite panel includes a fiberboard substrate including wood fiber and waterproof resin. At least one veneer is disposed over a first face of the fiberboard substrate. A waterproof adhesive is disposed between the veneer and the fiberboard substrate. In another example, a door assembly includes a door having at least one panel cavity. An insulation core is disposed within the at least one panel cavity and coupled to the door. At least one panel is disposed within the at least one panel cavity and coupled to the door. In one option, the at least one panel includes a fiberboard substrate including wood fiber and waterproof resin. The fiberboard substrate includes at least one face. A first veneer is coupled along at least one surface to the at least one face of the fiberboard substrate. In another option, a second veneer is coupled along at least one surface to another face of the fiberboard substrate. Optionally, the second veneer is substantially adjacent to the insulation core.