Incessant building collapses in Anambra State Nigeria is posing serious challenges to all the stakeholders in the building industry - building consultants, governments, developers, landlords and users. This has evoked great concern to all key players of the building industry. Thus, this study assessed the causative factors of building collapses in one of the cases, a collapsed uncompleted 3-story building which was reported in Oko town, Anambra State, Nigeria. A qualitative methodology involving subsoil and geotechnical investigation and also destructive testing of collapsed structural elements including sandcrete blocks, concrete and reinforcement bars; to establish the subsoil conditions, compressive strength, the yield stress as well as ductility of the reinforcements bars was adopted for this study. The results of the test carried out on the mass concrete, revealed a compressive strength ranging from 1.4N/mm2 to 3.1N/mm2 (standard compressive strength of 25N/mm2), 6” solid block ranging from 0.3N/mm2 to 0.4N/mm2 and 6” hollow block ranging from 0.2N/mm2, (standard strength value of 1.5 N/mm2 for a non-load bearing sandcrete block in accordance to NIS: 587:2007). The tensile stress of the reinforcement bars (12mm and 16mm) ranging from 280.29N/mm2 to 303.91N/mm2 (According to NIS: 117:2004, standard yield stress value of 410N/mm2 and ductility of 12%). The CPT revealed that the subsoil is generally too soft and the fine aggregate (sand) was poor for concreting. The findings suggest that poor foundation structure, inappropriate mix of concrete, the use of substandard materials, inadequate reinforcement and poor project supervision, contributed to the structural failure that lead to the collapse of the building. Therefore, this research recommends that mandatory, periodic or conditional structural integrity assessment of buildings in use and under construction becomes an exclusive preserve of highly qualified construction professionals. Standard organization of Nigeria should be vigilant to ensure that building materials imported into the country conforms to standard requirements especially the reinforcement bars.

Building defect is an issue in existing buildings that needs urgent tackling to prevent further problems. This study assessed the defects in concrete elements in residential buildings of 30 years and above in the Onitsha metropolis of Anambra State, Nigeria. Data collection instruments in the study include structured questionnaire, interviews, visual inspection/observations, archival records, recordings, photographs; and non-destructive testing of the concrete elements in an existing building in the study area. The population of this study constituted of the construction registered professionals and the existing buildings in study area. The sample for the study was based on the calculated sample size using Taro Yamani Formula. A total of 158 registered professionals were sampled from the population of 260. The questionnaires were purposively distributed to the registered professionals up to the required sample sizes of 158 and 129 questionnaires were properly filled and returned. The study used the SPSS and Microsoft Excel to analyze the data. The results were analyzed in percentages and figures using descriptive statistics and presented in the form of pie charts and tables. The finding of the study revealed that the causes and effects of structural defects on the concrete elements in existing buildings in the study area according to the rating are; exposed/corrosion of the embedded metals, faulty workmanship, overload and impacts, chemical attack, freeze-thaw deterioration, fire/heat, restraint to volume change. The visual observation revealed that the structural elements are characterized by heavy defects such as deep vertical, horizontal and diagonal cracks, exposed/ corrosion of the embedded metals, spalling of the concrete slabs. The existence of defects in the concrete members led to the low compressive strength of the concrete elements and the structural instability of the existing buildings How to cite this paper: Obiora, C.O.,