Comprehensive Risk Assessment for Engineering, Procurement, and Construction (EPC)-Based Prefabricated Buildings Using Analytic Network Process (ANP)–Gray Clustering Analysis

China’s prefabricated construction industry, despite its recent emergence, faces challenges such as limited standardization, poor integration, and low industrialization. In the Engineering, Procurement, and Construction (EPC) model for prefabricated buildings, numerous risks arise due to the long project lifecycle, complex technical requirements, and force majeure factors. These risks may cause substantial project losses if not effectively controlled. This study, from the perspective of general contractors, explores risk assessment for prefabricated building projects under the EPC model to promote construction practices and enhance project resilience. The objective is to help contractors mitigate risks and ensure the smooth and environmentally responsible implementation of prefabricated projects. Risks were identified through literature review and case analysis, and a statistical process refined them into a structured index. The Analytic Network Process (ANP) was applied to assign indicator weights, establishing a comprehensive risk evaluation model. The Gray System Theory was then employed to assess the risks in a case study from Southwest China, validating the effectiveness and applicability of the proposed model. This research provides a systematic approach and theoretical support for EPC-based risk assessment, offering guidance for risk management and contributing to development in the construction industry.