Wire Arc Additive Manufacturing (WAAM) is one of the lesser-known metal 3D printing technologies. The metal wire is melted with an electric arc as the heat source, thus the technique has a huge potential for large 3D metal parts with complex design in many industrial applications using less material. One of the limitations of this technique is residual stresses. This study shows how the process can be studied coupling several techniques, measuring residual stresses thanks to neutron techniques, which are able to analyse thick pieces without any destruction.