Public building stock in Turkey is getting older and more funds are transferred for repairs and maintenance of these public buildings. Parallel to this growth, a significant increase is observed in the number of occupational accidents occurring in the Turkish construction sector. This case study focuses on compulsory investments in small or middle-scale repairs and maintenance projects of public buildings. In the determination of occupational health and safety (OHS) costs which are an integral part of the project costs, a model combining risk-based activity analysis and activity-based cost analysis is utilized and computer software developed as a calculation instrument for this model is used. The ratio of actual and estimated OHS costs to the approximate cost was found to be 3.98 and 3.58%, respectively. Further research should be conducted to test the reliability of this model and its calculation tool in estimating the actual OHS cost before the tender stage.