Tsunami, impulse-waves and dam-break waves afflict humanity with casualties and damages. An insight into the flow mechanisms of these waves is important to provide safety and reduce reconstruction costs. This experimental study focuses on the effect of bed roughness on the main hydrodynamic properties of surges propagating on dry bed. In addition, the resulting wave impact forces on buildings with and without openings are studied. Results pointed out that dry bed surges on a rough bed had a lower front celerity and a higher flow depth, resulting into inundation depths during the impact around 20% higher as compared to the smooth bed. Furthermore, a rough bed induced a lower momentum flux during wave propagation, resulting into lower impact forces exerted on the building. The rough bed configuration also caused shorter impact durations, leading to lower impulse values transferred to the building. Results pointed out that even on rough bed, openings within the buildings linearly reduced impact forces, thus providing some helpful information for the design of safer coastal structures.