Ground Penetrating Radar (GPR) is a non-destructive technique widely used to investigate buildings and structures when direct or invasive inspections are not possible. Its application is particularly valuable in historical buildings, where preservation requirements limit destructive testing. However, the interpretation of GPR data can be challenging because different hidden features may generate similar radar responses. To address this issue, numerical modelling can be used to support interpretation by providing controlled simulations of electromagnetic wave propagation within structural elements. This thesis focuses on the investigation of the front façade of the Chiesa di San Giuseppe in Turin through the combined use of experimental GPR surveys and numerical modelling.