Cases of collapsed buildings have been on the increase in the city of Port Harcourt and environs in Rivers State, in particular and other major cities in Nigeria in recent times. A critical evaluation of the modes of failures indicates that absence of and / or inadequate subsurface geotechnical investigations have been responsible for these building foundation failures. Case histories of four major building foundation failures within the municipality of Port Harcourt and environs in the southern Niger Delta sub-region of Nigeria in recent times are presented and discussed in this paper. The first case history involves a five-storey building that collapsed because it was constructed across a river channel that had sand and gravels as major subsurface materials beneath the building site. As a result of excessive increase in groundwater table during the rainy season and the attendant excessive pore water pressures build-up that led to a rapid loss of the bearing strength of the subsurface materials, it collapsed in the form of a “punching failure”. The second case was a bearing capacity failure due to rapid construction that did not leave enough time for the dissipation of pore water pressures to allow the foundation soils gain shear strength. It collapsed soon after construction was completed. The third case failed as a result of lack of sufficient time to allow for curing of the block materials used for the building. This was a case of structural failure. The fourth case failed as a result of a complete lack of soil investigations that prevented a detailed foundation design for the residential buildings near the banks of a creek at Opobo town, a suburban settlement along a tidal creek. The paper presents and discusses in details the geology, hydrogeology and modes of failures of these four structures and draws attention to the need to carry out detailed subsurface investigations and abide within the building codes (if any)
