This study presents a customized root cause analysis approach to investigate the reasons, provide improvements measures for the cost overruns, and schedule slippage in papermachine- building projects. The proposed approach is an analytical-survey approach that uses both actual technical data and experts’ opinions. Various analysis tools are embedded in the approach including: data collection and clustering, interviews with experts, 5-Whys, Pareto charts, cause and effect diagram, and critical ratio control charts. The approach was implemented on seven projects obtained from a leading international paper machine supplier. As a result, it was found that the main causes behind cost and schedule deviations are products’ related; including technical accidents in the Press section, damaged parts, design issues, optimization of the machine and missing parts. Based on the results, prevention measures were perceived.