Tsunamis, impulse waves, and dam-break waves are rare but catastrophic events, associated with casualties and damage to infrastructures. An adequate description of these waves is vital to assure human safety and to generate resilient structures. Furthermore, a specific building geometry with openings, such as windows and doors, reduces wave-induced loads and increases the probability that a building withstands. However, waves often carry a large volume of debris, generating supplementary impact forces and creating debris dams around buildings, limiting the beneficial effects of the openings. Herein, a preliminary study on the three-dimensional (3D) effect of debris dams on postpeak wave-induced loads under unsteady flow conditions is presented based on laboratory experiments. Both wooden logs (forest) and shipping containers were tested, showing different behaviors. Shipping containers were associated with severe impact force peaks, whereas the interlocking nature of forest-type debris provoked a compact debris dam, leading to higher and longer-lasting hydrodynamic forces. The arrangement of the debris also had an influence on the resulting structural loading. All tested scenarios were analyzed in terms of horizontal force, cantilever arm, and impulse acting on the building. This study presents a methodology to support the evaluation of postpeak debris-induced loads for the design of safer resilient buildings.