The majority of the Tehran metropolitan region’s problems are associated with building contraventions, which intensified after migration from other parts of the country to the region increased. This migration coincided with a boom in the construction sector and an increase in density selling by the Tehran municipality.

Because of the far-reaching consequences of this phenomenon and the Tehran municipality’s inefficient and inappropriate building controls, it is important to identify the reasons and origins of these contraventions so that solutions and mitigation measures can be developed.

After conducting a literature review and a questionnaire study, the reasons for the occurrence of one of the most common building contraventions, namely non-compliance with floor area ratio (FAR) regulations, are discussed in this paper. The questionnaire investigated the following indicators: level of awareness, violation of regulations to meet the minimum needs of housing (housing-related motives), violation of regulations with the aim of gaining financial profit (profit-making motives), owners’ income level, the experience and expertise level of the developers, and the quality of supervision and monitoring. The questionnaire was answered by 150 persons whose cases were under investigation in the municipality, and the results were utilized to evaluate each of the above-mentioned indicators. A Pearson correlation test and a path analysis were used to analyze the data. The study revealed that developers’ level of awareness is the most influential factor leading to non-compliance with FAR requirements. Following this indicator, income level and housing-related motives have the greatest influence on non-compliance with FAR regulations.