Welder used 12mm of rod instead of 16mm for a building of 2 storey, what should I do?

Hello Adeshina! Sorry for the late response and Thank you for seeking support from our platform. Regarding your question, if the specification of the building supposed to be 16mm reinforcement bars (rods) and you spelt it accurately to the welder yet he used 12mm rods instead. Then you have the right to reject it and compel the welder to use the specified 16mm. However, if the 12mm rods have been used already to erect the storey building, be aware that the structural integrity of the building is at stack unless if doubled number of the 12mm rods were used for each pillar and lintels. The key and truthis to adhere strictly to the specifications of the civil engineer. Thank you and let us know if we are able to hit the answer you are looking for.