Structural failures occur worldwide. Various investigations have concluded that the primary causes of failure were design and construction errors within the building process. However, the exact factors that played a significant role were not clear. Therefore, the primary focus of this study is to improve structural safety by determining the influencing factors for structural safety within the design and construction process. First, a theoretical framework was developed, based on safety science and management literature. In particular, the concept of critical success factors, the factors within projects that are essential to reach the stated goals, appeared to be useful for this research. The factors mentioned in the literature played a role within some documented structural failures in the Netherlands. Based on this framework, a questionnaire was established. In this questionnaire, participants from the building industry were asked to indicate the extent to which factors from the theoretical framework were present in successful and less successful projects. In addition, they were asked to select the greatest determining factors for structural safety, in their opinion, from a list of possible factors. The results were statistically analyzed. Factors concerning the interrelations between various project partners had the largest impact on structural safety: communication and collaboration, control mechanisms, allocation of responsibilities, structural risk management, safety culture, and knowledge infrastructure. These factors will be designated the critical factors for structural safety, which are essential to assure structural safety within projects.