A wall board is produced based on a body element, which essentially has the shape of a rectangular parallelepiped including two opposing main sides and four edge sides according to the following method: mechanical surface processing of a first edge side, wherein the first edge side attains a flat surface structure, which extends from a first to a second of the main sides; applying a first surface treatment layer on the first edge side; and arranging a first edge strip along the first edge side. The first edge strip contains: a first distal edge surface, a thereto opposing first proximal edge surface which is flat, and a first primary surface between the first proximal edge surface and the first distal edge surface, The first edge strip being arranged with the first proximal edge surface against the first edge side such that the first primary surface and the first main side of the body element form a first, flat and essentially unbroken surface. A first reinforcement layer is also applied on the first, flat and essentially unbroken surface, which first reinforcement layer covers the first main side and the first primary surface.