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In the last two decades, building collapse has been a recurrent environmental hazard in Nigeria. This is a consequence of inadequate foundation investigation prior to construction, poor government policies, and general lack of awareness on the importance of geophysical and geotechnical investigations. In this study, geological mapping and detailed geophysical investigation using Electrical Resistivity Imaging (ERI) and Vertical Electrical Sounding (VES) were carried out to understand the suitability of proposed building sites at the main campus of the OOU, Ago-Iwoye, Nigeria for construction. Both Wenner array and dipole-dipole were used for profiling and Schlumberger for sounding. Four transverses and VES were used in each of the three areas investigated. The results show that the subsurface of the study areas is underlain by Precambrian basement rock of Nigeria. The sounding stations across the three areas and 2D resistivity imaging revealed three principal geoelectric layers, the topsoil, the weathered layer and the fractured/fresh basement with varied resistivity values for each layers. Our work demonstrates that some of the proposed sites are structurally incompetent for engineering or foundation purposes. Excavation of the topsoil and reinforcement are required to sustain the proposed structures.