Building-failure usually results to collapse if not discovered and properly addressed. Building-collapse/failure most times cause loss of properties and lives. A case study of a partially-collapsed one-story building is presented for emphasis with technical-assessment of the actual collapse cause so as to proffer remedy of the structure. This is achieved through detailed engineering-analysis of the building’s structural-elements and identification of remedial-options. Field-inspection through excavation of the soil to assess the foundation condition, taking soil-samples from the collapsed-building for laboratory study and non-destructive test. From inspection, it was observed that the building construction was not properly supervised and as a result were under-reinforced, which led to excessive cracks and deflection. The soil is classified by AASHTO as A-2-4; maximum-dry-density of 2.15mg/m3 and optimum-moisture-content of 9%. The compressive-strength of the structural elements were measured using the rebound-hammer and a mean compressive-strength of 13N/mm2 was obtained which indicates a low-compressive-strength concrete. Analytical-hierarchical-process is utilized as the multi-criteria decision making method to derive the actual cause of the collapse and from the priority vector 6%, 56%, 26% and 12% was obtained for soil/foundation, under-reinforcement, low-compressive-strength and overloading alternatives respectively. The consistency-ratio was obtained to be 0.065 this showed that the decision-maker’s subjective assessment is consistent. The summary of the failure investigation underscored the importance of ensuring proper supervision and quality control in the construction of framed structures. The remediation measures outlined are engagement of experts to re-design the structure using relevant-codes; then cracking, chiseling, and excavation to re-build the structure with thorough supervision.