The study analyzed actual construction costs of public apartments from 2004 to 2010 to identify and quantify irregular cost risks. By comparing actual costs with initial budget estimates, the researchers found that the biggest cost overruns occurred in outsourced labor and materials. Roofing and tiling work posed high outsourcing risks, while steel and cement were high-risk materials. The study also revealed that the lowest bidding system had drawbacks in cost analysis. The findings can help improve budget planning and risk management for future public housing projects.