Disclosed herein are plaster boards having a first surface and an opposing second surface, and a first edge and an opposing second edge that bound the first surface and the second surface. The first surface includes a first section and a second section, the first section being raised compared to the second section, the second section abutting the second edge. The second surface includes a first section and a second section that are separated by a boundary between the first edge and the second edge. The first section of the second surface is substantially parallel to the first section of the first surface. The second section of the second surface slopes toward the first surface from the boundary toward the second edge. Methods for making the plaster boards involve forming wet plaster material and drying the wet plaster material such that the wet plaster material hardens into a plasterboard.