Causes of variability in the execution time of processes in different construction systems

Abstract One of the major challenges faced by construction management is the implementation of activities within schedule, as variability often occurs. This research study aims to analyse the causes of variability in the execution time of processes in different construction systems, classifying them into different risk levels. The methodology consisted of a field study, where a questionnaire with 31 causes of variability divided into categories was applied to several construction workers. Our aim was to detect the frequency and intensity of delays. The study analysed reinforced concrete works (conventional), structural masonry and concrete walls cast on-site. For the data analysis, a delay factor was created and we classified the causes into risk levels by using cluster analysis. The results showed the main causes of variability for each one of the systems, and pointed to similarities: rework, low quality of work, socialisation. Statistical analyses showed differences between systems: the more industrialised systems had a greater number of causes classified at high-risk levels, but the impact of variability in the process was smaller. The study also showed deficiencies, on the part of managers, to deal with the impacts of process variability.