During the last few years, several major accidents during the construction phase have occurred in the Dutch building industry. The collapse of a roof structure of the FC Twente football stadium and the collapse of a concrete floor of the B-tower Rotterdam are some recent examples. Consequently, Dutch contractors do need to establish a reliable building process to prevent this kind of accidents. The main research question of this study was: “Which factors in the design and construction process influence structural safety at a single company?” Based on a previously published list of possible critical factors for a building project (Terwel & Vambersky, 2012), a questionnaire was developed in which 61 participants rated the contribution of these possible factors on structural safety in successful and in less successful projects on a five point Likert scale. Significant differences in the rating between successful and less successful projects indicated the relative influence of the specific factor on structural safety. Statistical analysis showed that Collaboration, Allocation of responsibilities, Risk analysis and allocation, Communication, Safety culture, Control mechanisms and Knowledge infrastructure were the most influencing factors concerning structural safety. The company was advised to improve these factors to reduce the number of failures in their construction processes in the future.