Prediction methods are required for designing buildings to protect inhabitants against ground-borne (structure-borne) noise from railway lines or other outdoor ground vibration sources, according to national regulations, guidelines or recommendations. There is no European standard for such predictions yet, but a European task group (CEN/TC126/WG2/TG1) is now doing preliminary work on this subject. A recent standard (EN ISO 20270) on field characterization of vibration sources opens a way for tackling the problem, based on the source-receiver vibration system methodology and using a mobility approach. In this paper, the approach is applied to ground-borne sound in buildings, where the building foundations in contact with ground are considered as the source and the building upperstructure the receiver. Two challenges are identified: one concerns the transmission of vibration power to the building upper-structure not only by flexural waves as with service equipment, for which a standardized prediction method exists, but also by in-plane waves; the second challenge arises from the complexity of the ground vibration field and the coupling between ground and building foundations, leading to difficulties in estimating the source activity.