Historical-cultural heritage is a testimony to the formation of people and should be preserved to maintain their identity over time. Thus, historical buildings are part of this heritage and should be valued and kept in exemplary conservation, use, and safety conditions. In this regard, the importance of Diagnostic Engineering in reducing constructive anomalies and associated costs of technical assistance is evident. This field utilizes essential tools, such as visual inspection, which evaluates the technical conditions for the use and maintenance of buildings. Additionally, Non-Destructive Testing (NDT), such as infrared thermography (IRT), is a powerful tool for non-invasive detection of constructive flaws in historical buildings. In this context, the objective of this study was to conduct visual inspections and identify pathological manifestations in a historical building in the city of Quixadá, Brazil. This is applied research with objectives fitting descriptive and exploratory research, a qualitative-quantitative approach, and a procedure classified as a case study. Thus, on-site visual inspections of the building were carried out, the pathological manifestations were classified according to the parameters of the GUT Matrix and Delphi Method, and an analysis of manifestations related to humidity was conducted through IRT. It was concluded that the historic building is in a critical state of conditions of use, representing risks to the safety of users, and is prone to accidents and structural collapses. As a contribution, this research represents a robust analysis based on Diagnostic Engineering and the use of IRT to analyze pathological manifestations in historical-cultural buildings.