Construction projects aim to achieve a set of specific goals, when achieved the project can be described as successful. Thus, any obstacle for achieving these goals represents a challenge to the project. The execution phase of the project is the most critical and drains the resources during project life cycle. Therefore, it requires more expertise for monitoring and controlling to overcome the obstructions and achieve the desired goals. The main objectives of the study: to diagnose the actual reasons behind mismanagement of the project execution phase, to measure their impact on cost and then to develop appropriate actions and treatments.