Purpose The purpose of this paper is to perform a quantitative analysis of the literature in order to determine the main causes of delay in construction projects. Design/methodology/approach A set of 47 articles from the literature were analyzed, yielding 1,057 different causes of delay. In order to analyze and compare the main causes of delay, their degree of impact was studied statistically. Next, a mention count method was used to determine the primary causes of construction project delays and through the use of Pareto diagrams, the main causes of delays in construction projects were determined. Findings It was determined that the three main causes of construction project delay are problems that occur during execution, administrative problems and labor conflicts; together they account for almost 80 percent of the causes found in the literature. Moreover, it was deduced that problems during execution are based on unpredictable events, while administrative problems are rooted in poor cash flow management. In addition, seven sub-groups of delay causes were identified as being major due to the number of mentions detected. These were "Changes during construction," "Poor construction management," "Construction errors," "Economic/Financial," "Conflict/Relationship" and "Lack of experience." Social implications Identifying the factors and causes of the delays will allow mitigation actions to be taken in order to avoid delays, which will ultimately allow homes, schools, hospitals and other necessary infrastructure to be delivered on time or even before the planned date. Originality/value This study provides a unique classification method that was successfully validated. Thanks to the classification, designers may use this information as a starting point for designing future construction projects, thereby minimizing unforeseen events during construction.