This paper presents a standardized methodology to analyze the impact of disasters on the functionality of healthcare systems post-disaster. The methodology to collect loss-of-function data was developed in 2010 and tested after the Bío-Bío, Baja California, and Christchurch earthquakes of 2010 and 2011. The survey tool collects field data on the performance of critical building systems and infrastructure, assesses the impact of system and infrastructure failure on the ability of hospitals to keep functioning, and provides data that can enhance existing and future tools to assess the performance of healthcare facilities. These survey tools can be used by other reconnaissance teams to collect data from both the healthcare and engineering perspectives, as well as an event tree which links the two perspectives together. This multi-disciplinary approach, involving engineers, epidemiologists, and health and emergency managers, is necessary to properly analyze how structural and non-structural damage disrupts essential services provided by hospitals.