In this study loading characteristics of rubble mound breakwater crown walls are investigated. This is done using a 2D physical model, testing for overall stability (through sliding) and temporal & spatial distributions of pressure along the face and base of the crown wall. A variety of wave conditions and geometries is used, with special attention for the influence of foundation level on the loading characteristics. This study shows the importance of this parameter and its link to the time lag between the maximum horizontal force and maximum vertical force in a wave impact. Using a new analysis method based on the factor of safety, this time lag is quantified and a reduction factor for the vertical forces is introduced.