This chapter presents the forensic investigations relevant to the collapse of a building in ‘aggregate’ that occurred in Barletta (Puglia, South Italy) on the morning of the 3rd October 2011, causing five fatalities. According to the Italian technical standards, a building aggregate consists of a set of adjacent buildings that is the result of an articulated and not unitary genesis due to multiple factors. Some recent Italian collapses, such as that occurred in Barletta, have highlighted that the approach to be used in the relevant forensic investigations is not so obvious and simple. The aim of the article is to describe the different approaches used in the investigations by different consultants and their different conclusions on the trigger of the collapse.