The interaction between a falling hammer on a floor system is considered as well as the interaction between a foot and a floor system during a “normal” step. The two cases involve two contact conditions. The first one implies some type of rebound condition whereas the later one a stuck to the floor condition. The floor system is mainly governing by the dynamic behavior of the floor cover. In the model for the cover an air-gap is included, which is often found in practice since it is almost impossible to obtain perfectly plane layers and floor surface. The influence of the airgap is studied.