Abstract: A wallboard is formed with each of its abutting top and bottom surfaces extending from its rear surface substantially perpendicular thereto for less than 50%, preferably 371/2%, of the distance between the rear surface and the front surface. The wallboard has a convex curved surface extending from the termination of the abutting top or bottom surface to the front surface. When the abutting surfaces of two wallboards are disposed in abutting relation, a deep fill recess is formed between the curved surfaces of the two adjacent wallboards. The recess is filled with a sealing compound having a greater compression strength than the compression strength of each of the adjacent wallboards so that any compression of the wallboards is absorbed by the wallboards and not the sealing compound whereby no tape is required at the wallboard joint and no ridging occurs.