The construction industry in Saudi Arabia (KSA) suffers from delivering projects on the planned time with the determined budget due to delays and cost overrun. Previous researches shows that 70% of the projects in the Saudi market, comprising 662 projects estimated at $440 million in value, faced significant delays with a cost overrun. Therefore, the accuracy of estimating budget for a construction project is a critical factor in the success of any project. The cost estimation models, which estimate the construction costs early, are helpful in the preliminary design stage. Improved cost estimation techniques available to project managers will facilitate more effective control of time and costs in construction projects. Hence, the aims and objectives (1) identifying different factors that cause disputable claims from a contractor point of view. (2) Ranking these factors according to their relative importance to find out the most important factors. (3) Provide a proposed system (Cost-X with BIM) to improve the estimated cost for construction projects with avoiding converting claims into disputes. The expected outcome in this thesis is to identify the significant causes of construction claims and disputes from a contractor point of view to be early avoided accordingly. Second, the possibility of combining BIM with Cost-X is a proposed method in this thesis as a preventive action to avoid claims and disputes ahead occurs. Third, the expected outcome also is a benefit from the proposed system, which the system supposes to accurately analyse any commercial value of claim or dispute cases in the event of occurring under any circumstances.