Thesis (B.S.) -- Cagayan State University, 2025.

Cost overruns remain a persistent challenge in the construction industry, especially in institutional building projects, where complex variables often hinder accurate budgeting. This study aims to address this issue through the development of a predictive model using the Mamdani Fuzzy Inference System (FIS), an intelligent framework known for handling uncertainty and imprecision in decision-making. By identifying and analyzing key contributory factors such as design errors, external influences, time management, cost estimation, and project team competence, the research establishes a comprehensive model capable of estimating the probability of cost overruns. Data were collected from twenty (20) experienced project engineers operating in the Third District of Cagayan, covering institutional projects between 2015 and 2025. These data included both estimated and actual project costs, allowing for comparative analysis. The model utilized fuzzy logic principles-specifically fuzzification, rule-based inference, and defuzzification to evaluate linguistic input variables and generate a crisp output representing overrun probability. Results demonstrated that design and external factors were the most significant contributors to cost increases, while material and equipment management had the least influence. The model achieved a prediction accuracy of 85.71%, validating its effectiveness in anticipating cost deviations. One incorrect prediction highlighted the inherent unpredictability of the construction environment, reinforcing the need for integrated risk management. The study concludes that the Mamdani FIS is a viable tool for enhancing cost control strategies and offers practical value for construction professionals, clients, and project managers seeking to improve budget reliability and reduce financial risk. Recommendations include expanding the range of variables, increasing sample diversity, and refining fuzzy rules based on broader data. The findings underscore the critical role of intelligent systems in navigating the complexities of modern construction projects.

Keywords: cost overrun prediction, Mamdani fuzzy inference system,
construction risk analysis, intelligent project management, Cagayan Third District, fuzzy logic modeling