A method of erecting a building wall in 3D printing, said method comprising - that a 3D positioning apparatus, in particular a gantry robot, having a tool holder, to which a printhead is attached, is provided, - that an initially plastically deformable and then hardening building material, in particular a concrete, is fed to the printhead, and - that the building material is applied by means of the printhead along a predefined or predefinable printing path in that the printhead is moved along the printing path by means of the 3D positioning apparatus and outputs the building material in so doing, wherein the printing path extends in a plurality of horizontal layers, which are vertically offset in parallel with one another, and comprises a respective first section in each of said layers to form a first wall surface of the building wall, wherein the method further comprises - that at least one elongate reinforcing element is provided that extends along a longitudinal direction and that has a first side transverse to the longitudinal direction and a second side opposite to said first side as well as at least one passage opening which connects the two sides (33, 35) to one another, characterized in that - the at least one reinforcing element is fixed vertically oriented on a substrate such that it crosses the respective first section in at least some of the layers so that in each case a first part section (27, 29) of the first section adjoins one of the two mentioned sides (33, 35) of the reinforcing element and a second part section (29, 31) of the first section adjoins the other one of the two mentioned sides (33, 35) of the reinforcing element, and - in that the printhead, after it has been moved along the first part section (27, 29) towards the respective side (33, 35) of the reinforcing element and has output building material in so doing and/or before it has been moved along the second part section (29, 31) away from the respective side (33, 35) of the reinforcing element and has output building material in so doing, presses building material in at least one of the layers through the at least one passage opening onto the respective other side (33, 35) of the reinforcing element. - that a 3D positioning apparatus, in particular a gantry robot, having a tool holder, to which a printhead is attached, is provided, - that an initially plastically deformable and then hardening building material, in particular a concrete, is fed to the printhead, and - that the building material is applied by means of the printhead along a predefined or predefinable printing path in that the printhead is moved along the printing path by means of the 3D positioning apparatus and outputs the building material in so doing, wherein the printing path extends in a plurality of horizontal layers, which are vertically offset in parallel with one another, and comprises a respective first section in each of said layers to form a first wall surface of the building wall, wherein the method further comprises - that at least one elongate reinforcing element is provided that extends along a longitudinal direction and that has a first side transverse to the longitudinal direction and a second side opposite to said first side as well as at least one passage opening which connects the two sides (33, 35) to one another, - that at least one elongate reinforcing element is provided that extends along a longitudinal direction and that has a first side transverse to the longitudinal direction and a second side opposite to said first side as well as at least one passage opening which connects the two sides (33, 35) to one another, characterized in that - the at least one reinforcing element is fixed vertically oriented on a substrate such that it crosses the respective first section in at least some of the layers so that in each case a first part section (27, 29) of the first section adjoins one of the two mentioned sides (33, 35) of the reinforcing element and a second part section (29, 31) of the first section adjoins the other one of the two mentioned sides (33, 35) of the reinforcing element, and - in that the printhead, after it has been moved along the first part section (27, 29) towards the respective side (33, 35) of the reinforcing element and has output building material in so doing and/or before it has been moved along the second part section (29, 31) away from the respective side (33, 35) of the reinforcing element and has output building material in so doing, presses building material in at least one of the layers through the at least one passage opening onto the respective other side (33, 35) of the reinforcing element. - the at least one reinforcing element is fixed vertically oriented on a substrate such that it crosses the respective first section in at least some of the layers so that in each case a first part section (27, 29) of the first section adjoins one of the two mentioned sides (33, 35) of the reinforcing element and a second part section (29, 31) of the first section adjoins the other one of the two mentioned sides (33, 35) of the reinforcing element, and - in that the printhead, after it has been moved along the first part section (27, 29) towards the respective side (33, 35) of the reinforcing element and has output building material in so doing and/or before it has been moved along the second part section (29, 31) away from the respective side (33, 35) of the reinforcing element and has output building material in so doing, presses building material in at least one of the layers through the at least one passage opening onto the respective other side (33, 35) of the reinforcing element.