Lightning electromagnetic pulse (LEMP) is a severe threat to sensitive electronic devices installed in buildings. To protect these devices from LEMP effects, the evaluation of the electromagnetic fields inside of the building is required. Although numerous studies have been devoted to the analysis of these fields stemming from direct and indirect lightning strikes, no thorough study on the analysis of the electromagnetic environment inside a building with layered reinforcing bars has been presented in the past. In this paper, using the 3-D finite-difference time-domain method, we present a systematic analysis of the electromagnetic field inside a full-scale building associated with direct and nearby lightning strikes, taking into account the presence of reinforced concrete, to evaluate the effect of the structure of the reinforced concrete on the lightning electromagnetic fields.