The success of optimal system selection depends on many factors, such as the nature of the project itself, design team collaboration, team leader's personality, and client input. Unfortunately, despite numerous existing studies on key impacting factors in various fields of construction design, the majority of them failed to focus on the key factors affecting the structure design decision-making process. This study aims to identify, investigate, and rank factors perceived to affect decision-making for the optimal system in the construction industry, particularly that of buildings, during the early stages of the entire life cycle, in terms of their relative importance. Practitioners and experts from Egypt comprising a statistically representative sample, were invited to participate in a structured questionnaire survey to achieve this objective. The questionnaire was composed of 17 factors classified under three primary stage categories: feasibility study, planning, and design and engineering. The relative importance index and dispersion analysis were used to obtain statistics and calculate the collected data. The results show that “The impact of financial difficulties on the decision-making” is the first key factor, “The impact of errors and omissions due to the lack of communication and coordination on the decision-making” is the second key factor, and “The Impact of inaccurate evaluation of projects duration on the decision-making” and “The impact of design changes upon contractor request on the decision-making?” constitute the third key factors. Therefore, this work can guide decision-makers for effective construction management and help achieve a competitive quality and cost-effective project.