A set of scale-model tests was carried out at the wave basin of the Leibniz University Hannover to extend the range of wave steepness values analysed in run-up, overtopping and armour layer stability studies, focusing on oblique extreme wave conditions and on their effects on a gentler slope breakwater’s trunk armour and roundhead. The paper describes the model set-up and operation concentrating on the measurement techniques used in those tests, namely on the innovative techniques for armour layer damage characterization.