Described herein is a method for forming a monolithic surface in a ceiling system, the method comprising overlapping a first facing sheet and a second facing sheet to create an overlap region, each of the first and second facing sheets having a first major surface opposite a second major surface and side surface extending between the first and second major surfaces, wherein the lower surface of the first facing sheet contacts the upper surface of the second facing sheet within the overlap region, and running a blade of a cutting tool along the overlap region such that the blade extends through the first and second facing sheets at a cutting angle that is oblique to the first major surface of the first facing sheet within the overlap region.