AbstractConstruction nonconformity assessment of buildings is critical to ensure the anticipated quality and living safety for their future occupants. Previous studies have paid less attention to identifying and analyzing building construction nonconformities (BCNs) in the design and construction (D&C) phases. They considered expert judgments in nonconformity assessment, which are critiqued for human bias, uncertainty, and imprecision. In a BCN assessment, previous studies also did not consider the specific time frame to detect construction nonconformities. This study aims to prioritize nonconformities in the D&C phases, addressing the limitations of expert judgment by applying the fuzzy group decision-making approach (FGDMA). The FGDMA computes the defuzzified scores of the nonconformities to prioritize and identify critical nonconformities. The defuzzified scores are explained further by associating them with the corresponding fuzzy numbers to address the limitations involved in expert judgments. The study also identifies the detection time of BCNs and analyzes 15 different Bangladeshi project scenarios to understand their context better. The critical nonconformities identified include premature stressing on concrete, inaccurate water-cement ratios, insufficient concrete compaction, lack of full-time site supervision, and the absence of stirrups in beam-column joints. Critical nonconformities are mostly identified during construction, and residential, commercial, and multipurpose buildings, regardless of ownership (i.e., public or private) and size, have experienced poor quality construction. This study will assist major stakeholders (owner, contractor, consultant, and regulatory authorities) to fully understand the critical nonconformities in different building projects from their preconstruction to construction phases for better quality assurance in providing a safe living and working environment for their future occupants.Practical ApplicationsThe study identifies critical nonconformities and their frequency, severity, and detection times in different construction projects, including residential, commercial, and multipurpose buildings and mosques. It also studies 15 different project scenarios for analyzing the nonconformities of government and privately funded/owned buildings. The most common nonconformities are premature stressing on concrete (loading to concrete members before gaining their design strength), inaccurate water-cement ratios, insufficient concrete compaction, and the absence of stirrups in beam-column joints. These nonconformities all occur due to lack of full-time site supervision and poor workmanship during construction. The dominating detection time for identifying the critical nonconformities is “during construction.” Thus, it is possible to control many by careful supervision and improved workmanship during construction. The project scenario analysis shows that residential, commercial, and multipurpose buildings, regardless of ownership (i.e., public or private), experience poor quality construction. These findings will assist stakeholders with different engagement levels in managing their roles in building projects to deliver a better quality of construction, and hence a sustainable and safe living and working environment.