A ceiling system includes a grid support member, and first and second ceiling panels abutted at a joint. In the factory-supplied condition, each panel has a facing sheet already adhesively bonded to a central region of the panel. Perimeter portions of the facing are left un-bonded to an annular peripheral region of the surface surrounding the central region. This allows seams to be made in the field. The facing sheet comprises a cantilevered flap extending beyond a peripheral edge of the panel. During field installation, the flap of a first panel extends across the joint overlapping the second panel's un-bonded facing sheet in the peripheral region. The double thickness of facings is cut to form a seam laterally offset from the joint, which is concealed. A field applied or activated adhesive bonds the facing to the peripheral regions of each panel. A related installation method is disclosed.