Hospitals are a critical element of the healthcare system and their continuous function is highly important to the wellbeing of communities. In accordance with the criticality of their functional performance during disruptive events, several modelling and analysis approaches have been developed to investigate the extent of various aspects of hospitals’ vulnerability and resilience. However, these approaches fall short in addressing either the degree of absorption, adaptation and, in some cases, degradation of the hospital as a system before its fundamental breakdown or fail to differentiate their performance in normal conditions versus surge circumstances and protocols. In this paper, these issues were addressed via deployment of the Functional Resonance Analysis Method (FRAM) and a macro analysis of the interactions among hospital system functions under surge conditions. The use of FRAM as the modelling technique helps to address the extent of system adaptability to changes and explore the hidden impact of different functions on overall system performance. The modelling involved identification of surge functions and fulfilment of conditions for the functions generating the outcomes. The study identifies the limitations existing in hospital surge procedures and highlights the difference between work-as-imagined and work-as-done regarding hospital surge procedures.