Structural defects such as joints or faults are inherent to almost any rock mass. In many situations such defects have a major impact on slope stability as they can control the possible failure mechanisms. Having a good estimate of their strength then becomes crucial. The roughness of a structure is a major contributor to its strength through two different aspects, the morphology of the surface (or the shape) and the strength of the asperities (related to the strength of the rock). In the current state of practice, roughness is assessed through idealised descriptions (Patton strength criteria) or through empirical parameters (Barton’s JRC). In both cases, the multi dimensionality of the roughness is ignored. In this study, we propose to take advantage of the latest developments in numerical techniques. With 3D photogrammetry and/or laser mapping, practitioners have access to the real morphology of an exposed structure. The derived triangulated surface is then introduced into the DEM code PFC3D to create a synthetic rock joint. The recent one development of the Smooth Joint Model (SJM) allows to get rid of the artificial roughness introduced by the particle discretization. Shear tests are then performed on the synthetic rock joints. Amongst the benefits of the methodology is the possibility offered by DEM to reproduce the progressive degradation of the asperities upon shearing and analyse structures of different scales without introducing any empirical relation.