A panel system includes a first skin, a second skin, a web core constructed from sheet material for securing the skins together in a spaced, sandwich relationship, and a connecting means for affixing the web core within the skins. The web core includes a plurality of spaced apart longitudinal members having longitudinally spaced projections extending therefrom and further having transversely aligned, longitudinally spaced slots therein. The web core further includes a plurality of spaced-apart, transverse cross members each having spaced slots therein receiving the longitudinal members at corresponding transversely aligned slots thereof to provide an interlocked grid work between the first and second skins. The grid is connected to the skins utilizing the projections, which extend through slits in the skins in one embodiment to facilitate welding or otherwise bonding the components. In a second embodiment the projections present mounting ears that receive fasteners that extend through the skins.