The importance of assessing the overall behaviour of buildings considering the contribution of non-structural infills has been nowadays widely recog-nised. Indeed, infills can trigger fragile mechanisms of structural members preventing the evolution of dissipative mechanisms and can play an im-portant role in the verifications at damageability limit states, especially in the case of strategic structures for which often high performance levels are re-quired, including the full operativity (i.e. absence of damage to both struc-tural and non-structural members) after severe earthquake, in order to guar-antee the building occupancy during the emergency management. With reference to a case study, the paper presents a simplified approach for estimating the stiffness of masonry infill walls through expeditious dynamic impact tests on infills. The case study is constituted by a laboratory real-scale mock-up for which a complete dynamic identification is carried out before and after the realization of infill masonry walls. The adopted procedure is then validated through results from a refined finite element model of the mock-up in which infills are modelled adopting stiffnesses obtained from the proposed approach.