Assessment of Cause–Effect of Design Defects in the Implementation Phase of Construction Projects

Design-related risks negatively affect construction project performance, in which design defects (DD) are considered as one of the most important risks. Previous studies provide a diverse list of important factors related to DD. However, very few of these studies have examined the interactions between factors in a cause–effect relationship. Identifying individual factors based on their importance can make it difficult to propose mitigation or prevention solutions. This study provides the important factors related to DD based on their interactions by combining the rules of systems thinking for iterative cause loop–diagrams (CLD) and Decision-Making Trial and Evaluation Laboratory (DEMATEL). The research results showed that ‘poor design consultancy’, ‘lack of checking and approval during the design process’, ‘lack or error of data before design’, and ‘careless, irresponsibility’ are the main causes of DD. At the same time, DD greatly influence project efficiency, which is reflected in factors such as ‘rework during construction’, ‘slow completion of the project’, ‘cost overrun’, and ‘rework of design documents’.