The most recent windstorms in Europe have shown that the wind can cause significant damage such as truss wall failures, or more frequently, the removal of roof elements. In this context, a pre-normative study by the Belgian Building Research Institute and the von Karman Institute, has been carried out to measure the unsteady pressure fields on roof tiles under different wind conditions. The objective is to design new guidelines for the Belgian NBN norm and the Eurocode 1, relating to the forces acting on the external part of the roof. Experiments have been performed both on a full-scale model (FSM) and on scaled down models (SDM). Test conditions and results are discussed: the wind conditions including the real and the wind tunnel atmospheric boundary layer, the steady and unsteady pressure fields under and on the roof and finally the resulting extremum Cp coefficients. The extremum Cp coefficients are obtained by searching for each wind direction the minimum and the maximum Cp encountered on the roof.