A method for producing a three-dimensional construction material component preferably having at least one curved surface. A plurality of spacers are arranged in a formwork. A textile reinforcement is supported on the spacers, such that the textile reinforcement has a defined position within a formwork interior of the formwork. A tensile force is applied via a tensioning device to the textile reinforcement in at least one tension direction. Construction material is introduced into the formwork interior and surrounds the textile reinforcement. The construction material is then hardened, wherein the tensile force is maintained during the hardening. During this process, the spacers are integrated into the construction material component. The tensioning device has at least one clamping unit for clamping an end portion of the textile reinforcement between two clamping surfaces. The clamping surfaces are provided on clamping insert bodies, which are of a plastic material of a defined hardness.