This article investigates the cause of the failure of some parts of a
two-storey building under construction, in Oba-Ile, Akure, Ondo State, Nigeria. The
article examines the effect of the quality of sand used for concrete production on
the quality of concrete produced from them. The article also investigates whether
the provided main and shear reinforcements in buildings complied with the
provisions of the BS 8110 . Site inspections were carried out, and concrete samples
were taken. Many of the structural components were exposed, so as to determine
the number of reinforcements in each structural element, the anchorage length
of main reinforcement provided and the spacing of shear reinforcement. The fi eld
settling method was used to determine the percentage content of silt / clay impurity
in the sand. The average silt / clay content of the sand was found to be 10.5 per cent,
which is above the maximum 4 per cent value stipulated by the code. The results of
both the destructive and non-destructive tests show that the average compressive
strength of the concrete is 9.6 N / mm 2 , which is less than 20 N / mm 2 specifi ed
minimum concrete strength for structural use. The anchorage length provided
is less than the value stipulated by the code. The low quality of the concrete is
due to the high percentage content of silt / clay in the sand used. From the above
investigation, the possible cause of the collapse of the building is the provision of
anchorage length less than required, spacing of shear reinforcement is less than
required and, the poor quality of the concrete used for the construction.

• Causes of structural failures of a building: Case study of a building at Oba-Ile, Akure