W ith the increase in population and the development of the property sector in Indonesia, the need and demand for development such as the need for building materials, one of which is steel, will also increase. PT. Buana Masa Metalindo is a company that excels in fabrication and construction. At the time of making a girder product, the entire production process is carried out by manually (manual operation) which still relies on the skills of the operator. During the production process, errors are still often made by operators, especially in the cutting, welding, and painting processes. The purpose of the research conducted at PT. Buana Masa Metalindo to determine the potential for human error in the customized girder production process, measure the possibility of human error (human error probability) in the customized girder production process and provide suggestions to minimize human error at PT. Buana Masa Metalindo. The method used to identify the task is with SHERPA, then to calculate HEP is using HEART and to assest risk control is using HIRARC. From the SHERPA method, there are 5 high probability activities. In the HEART method, the highest HEP value is 0.855 in activity 5.1. From these results, 80% of the highest HEP values were used for risk assessment and risk control using HIRARC and proposed improvements in the form of making a hygiene checklist and also the completeness of safety protective equipment.