Predicting extreme values of wall-pressure on a tall building is a crucial step in the design process of the building but can prove to be very challenging. This paper describes wind tunnel study with a well-defined mean velocity gradient and turbulent characteristics. The experiments were performed in the NSA wind tunnel at CSTB, Nantes, France, at a 1:300 scale. The tower building was modeled by a wall-mounted prism of square crosssection (dimensions: 10 cm x 10 cm x 49 cm) equipped with 265 pressure taps used to measure the unsteady pressure distribution on the model walls. Comparisons between different measurement methods of the global wind load are presented. Differences between lateral and longitudinal loads are discussed in link with the physics of the flow